Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications
The aim of the paper is to show the potential of the spectroscopic ellipsometry and magnetooptical (MO) spectroscopy for probing of the multilayered films (MLF) with sublayer thickness of about a few nanometres. The main approach applied by us is based on the comparison of the experimental optical a...
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| Published in: | Успехи физики металлов |
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| Date: | 2005 |
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Інститут металофізики ім. Г.В. Курдюмова НАН України
2005
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| Cite this: | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications / Yu.V. Kudryavtsev, V.M. Uvarov, R. Gontarz, J. Dubowik, Y.P. Lee, J.Y. Rhee, Yu.N. Makogon, E.P. Pavlova // Успехи физики металлов. — 2005. — Т. 6, № 2. — С. 135-168. — Бібліогр.: 62 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860218049124106240 |
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| author | Kudryavtsev, Yu.V. Uvarov, V.M. Gontarz, R. Dubowik, J. Lee, Y.P. Rhee, J.Y. Makogon, Yu.N. Pavlova, E.P. |
| author_facet | Kudryavtsev, Yu.V. Uvarov, V.M. Gontarz, R. Dubowik, J. Lee, Y.P. Rhee, J.Y. Makogon, Yu.N. Pavlova, E.P. |
| citation_txt | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications / Yu.V. Kudryavtsev, V.M. Uvarov, R. Gontarz, J. Dubowik, Y.P. Lee, J.Y. Rhee, Yu.N. Makogon, E.P. Pavlova // Успехи физики металлов. — 2005. — Т. 6, № 2. — С. 135-168. — Бібліогр.: 62 назв. — англ. |
| collection | DSpace DC |
| container_title | Успехи физики металлов |
| description | The aim of the paper is to show the potential of the spectroscopic ellipsometry and magnetooptical (MO) spectroscopy for probing of the multilayered films (MLF) with sublayer thickness of about a few nanometres. The main approach applied by us is based on the comparison of the experimental optical and MO properties with the simulated ones based on various models of the MLF. Specifically, as shown, such an approach can be useful for studying the nature of unusual MO properties and the interfaces in MLF comprising the noble and 3d-transition metals (3d-TM). The high sensitivity of the applied spectroscopic methods for the monitoring of the solid-state reactions in the 3d-TM/Si MLF induced by ion-beam treatment or by thermal annealing is also demonstrated. The optical properties of various silicides formed spontaneously or induced by various treatments at interfaces are evaluated experimentally and compared with the results of first-principle calculations.
В данной работе показаны возможности спектральной эллипсометрии и магнитооптической (МО) спектроскопии для изучения структуры и особенностей физических свойств многослойных металлических пленок (МСП) с толщинами составляющих слоев порядка единиц нанометров. Основной подход исследования базируется на сравнении экспериментально измеренных оптических и МО свойств МСП с модельными, полученными для различных моделей структуры МСП. Было показано, что данный подход позволяет выяснить природу необычных МО свойств, а также структуру интерфейсной области в МСП, состоящих из слоев благородных и 3d-переходных металлов (ПМ). Также в работе продемонстрирована высокая чувствительность спектральной эллипсометрии для изучения твердотельных реакций в МСП 3d-ПМ/Si, вызванных ионной бомбардировкой или термическим отжигом. Оптические свойства различных силицидов 3d-ПМ, сформированных спонтанно либо в результате различных воздействий на МСП, были изучены экспериментально и сравнены с результатами теоретических первопринципных расчетов.
В даній роботі показані можливості спектральної еліпсометрії та магнітооптичної (МО) спектроскопії для вивчення структури та особливостей фізичних властивостей багатошарових металевих плівок (БШП) з товщинами складаючих їх шарів порядку одиниць нанометрів. Основний підхід дослідження базується на порівнянні експериментально одержаних оптичних та МО властивостей БШП з модельними, що були одержані для різних моделей структури БШП. Було показано, що даний підхід дозволяє визначити природу незвичайних МО властивостей, а також природу інтерфейсної області БШП, що складаються з шарів благородних та 3d-перехідних металів (ПМ). В роботі також паказана висока чутливість спектральної еліпсометрії для вивчення твердотільних реакцій в БШП 3d-ПМ/Si, зумовлених іонним бомбардуванням або термічним відпалом. Оптичні властивості різних силіцидів 3d-ПМ, що було зформовані спонтанно або завдяки зовнішньому впливу, були вивчені експериментально та порівняні з результатами теоретичних першопринципних розрахунків.
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Óñïåõè ôèç. ìåò. / Usp. Fiz. Met. 2005, ò. 6, ññ. 135–168
Îòòèñêè äîñòóïíû íåïîñðåäñòâåííî îò èçäàòåëÿ
Ôîòîêîïèðîâàíèå ðàçðåøåíî òîëüêî
â ñîîòâåòñòâèè ñ ëèöåíçèåé
© 2005 ÈÌÔ (Èíñòèòóò ìåòàëëîôèçèêè
èì. Ã. Â. Êóðäþìîâà ÍÀÍ Óêðàèíû)
Íàïå÷àòàíî â Óêðàèíå.
PACS numbers: 75.70.-i, 78.20.Bh, 78.20.Ls, 78.66.-w, 78.67.-n, 79.20.Rf
Optical andMagnetoopticalSpectroscopy of theNanostructural
Multilayered Films: Possible Applications
Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz*, J. Dubowik*,
Y. P. Lee**, J. Y. Rhee***, Yu. N. Makogon****, and E. P. Pavlova****
G. V. Kurdyumov Institute for Metal Physics, N. A. S. of the Ukraine,
36 Academician Vernadsky Blvd.,
UA-03680 Kyyiv-142, STM, Ukraine
*Institute of Molecular Physics, Polish Academy of Sciences,
60-179 Poznan′, Poland
**q-Psi and Department of Physics, Hanyang University,
Seoul, 133-791 Korea
***Department of Physics, Hoseo University,
Asan, Choongnam, 336-795 Korea
****National Technical University of Ukraine ‘Kyyiv Polytechnic Institute’,
37 Pobedy Ave.,
Kyyiv, Ukraine
 äàííîé ðàáîòå ïîêàçàíû âîçìîæíîñòè ñïåêòðàëüíîé ýëëèïñîìåòðèè è
ìàãíèòîîïòè÷åñêîé (ÌÎ) ñïåêòðîñêîïèè äëÿ èçó÷åíèÿ ñòðóêòóðû è îñî-
áåííîñòåé ôèçè÷åñêèõ ñâîéñòâ ìíîãîñëîéíûõ ìåòàëëè÷åñêèõ ïëåíîê
(ÌÑÏ) ñ òîëùèíàìè ñîñòàâëÿþùèõ ñëîåâ ïîðÿäêà åäèíèö íàíîìåòðîâ.
Îñíîâíîé ïîäõîä èññëåäîâàíèÿ áàçèðóåòñÿ íà ñðàâíåíèè ýêñïåðèìåí-
òàëüíî èçìåðåííûõ îïòè÷åñêèõ è ÌÎ ñâîéñòâ ÌÑÏ ñ ìîäåëüíûìè, ïîëó-
÷åííûìè äëÿ ðàçëè÷íûõ ìîäåëåé ñòðóêòóðû ÌÑÏ. Áûëî ïîêàçàíî, ÷òî
äàííûé ïîäõîä ïîçâîëÿåò âûÿñíèòü ïðèðîäó íåîáû÷íûõ ÌÎ ñâîéñòâ, à
òàêæå ñòðóêòóðó èíòåðôåéñíîé îáëàñòè â ÌÑÏ, ñîñòîÿùèõ èç ñëîåâ áëà-
ãîðîäíûõ è 3d-ïåðåõîäíûõ ìåòàëëîâ (ÏÌ). Òàêæå â ðàáîòå ïðîäåìîíñ-
òðèðîâàíà âûñîêàÿ ÷óâñòâèòåëüíîñòü ñïåêòðàëüíîé ýëëèïñîìåòðèè äëÿ
èçó÷åíèÿ òâåðäîòåëüíûõ ðåàêöèé â ÌÑÏ 3d-ÏÌ/Si, âûçâàííûõ èîííîé
áîìáàðäèðîâêîé èëè òåðìè÷åñêèì îòæèãîì. Îïòè÷åñêèå ñâîéñòâà ðàç-
ëè÷íûõ ñèëèöèäîâ 3d-ÏÌ, ñôîðìèðîâàííûõ ñïîíòàííî ëèáî â ðåçóëüòà-
òå ðàçëè÷íûõ âîçäåéñòâèé íà ÌÑÏ, áûëè èçó÷åíû ýêñïåðèìåíòàëüíî è
ñðàâíåíû ñ ðåçóëüòàòàìè òåîðåòè÷åñêèõ ïåðâîïðèíöèïíûõ ðàñ÷åòîâ.
 äàí³é ðîáîò³ ïîêàçàíî ìîæëèâîñò³ ñïåêòðàëüíî¿ åë³ïñîìåò𳿠òà ìàã-
íåòîîïòè÷íî¿ (ÌÎ) ñïåêòðîñêîﳿ äëÿ âèâ÷åííÿ ñòðóêòóðè òà îñîáëèâî-
135
136 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
ñòåé ô³çè÷íèõ âëàñòèâîñòåé áàãàòîøàðîâèõ ìåòàëåâèõ ïë³âîê (ÁØÏ) ç
òîâùèíàìè ñêëàäàþ÷èõ ¿õ øàð³â ïîðÿäêó îäèíèöü íàíîìåòð³â. Îñíîâíèé
ï³äõ³ä äîñë³äæåííÿ áàçóºòüñÿ íà ïîð³âíÿíí³ åêñïåðèìåíòàëüíî îäåðæà-
íèõ îïòè÷íèõ òà ÌÎ âëàñòèâîñòåé ÁØÏ ç ìîäåëüíèìè, ÿê³ áóëè îäåð-
æàí³ äëÿ ð³çíèõ ìîäåë³â ñòðóêòóðè ÁØÏ. Áóëî ïîêàçàíî, ùî äàíèé ï³ä-
õ³ä äîçâîëÿº âèçíà÷èòè ïðèðîäó íåçâè÷àéíèõ ÌÎ âëàñòèâîñòåé, à òàêîæ
ïðèðîäó ³íòåðôåéñíî¿ îáëàñòè ÁØÏ, ÿê³ ñêëàäàþòüñÿ ç øàð³â áëàãîðîä-
íèõ òà 3d-ïåðåõ³äíèõ ìåòàë³â (ÏÌ).  ðîáîò³ òàêîæ ïîêàçàíî âèñîêó ÷óò-
ëèâ³ñòü ñïåêòðàëüíî¿ åë³ïñîìåò𳿠äëÿ âèâ÷åííÿ òâåðäîò³ëüíèõ ðåàêö³é ó
ÁØÏ 3d-ÏÌ/Si, çóìîâëåíèõ éîííèì áîìáàðäóâàííÿì àáî òåðì³÷íèì â³ä-
ïàëîì. Îïòè÷í³ âëàñòèâîñò³ ð³çíèõ ñèë³öèä³â 3d-ÏÌ, ÿê³ ñôîðìóâàëèñü
ñïîíòàííî àáî çàâäÿêè çîâí³øíüîìó âïëèâó, áóëî âèâ÷åíî åêñïåðèìåí-
òàëüíî òà ïîð³âíÿíî ç ðåçóëüòàòàìè òåîðåòè÷íèõ ïåðøîïðèíöèïíèõ ðîç-
ðàõóíê³â.
The aim of the paper is to show the potential of the spectroscopic ellip-
sometry and magnetooptical (MO) spectroscopy for probing of the multi-
layered films (MLF) with sublayer thickness of about a few nanometres.
The main approach applied by us is based on the comparison of the exper-
imental optical and MO properties with the simulated ones based on vari-
ous models of the MLF. Specifically, as shown, such an approach can be
useful for studying the nature of unusual MO properties and the interfaces
in MLF comprising the noble and 3d-transition metals (3d-TM). The high
sensitivity of the applied spectroscopic methods for the monitoring of the
solid-state reactions in the 3d-TM/Si MLF induced by ion-beam treatment
or by thermal annealing is also demonstrated. The optical properties of var-
ious silicides formed spontaneously or induced by various treatments at
interfaces are evaluated experimentally and compared with the results of
first-principle calculations.
Key words: spectroscopic ellipsometry, magnetooptical spectroscopy, multi-
layered films, solid-state reactions, ion-beam mixing.
(Received January 13, 2005)
INTRODUCTION
Recent discovery of new interesting physical phenomena (such as
oscillating interlayer exchange coupling, giant magnetoresistance,
unusual magnetooptical (MO) responses, quantum size effects) in the
magnetic artificial structures like multilayered films (MLF) com-
posed of alternated layers of ferromagnetic and nonmagnetic metals
has prompted intensive research in this field.
Among the metallic multilayers, a specific place occupy the MLF
composed of ferromagnetic 3d-transition metals (TM) (mainly Co
and Fe) and heavy noble metals (NM) because of the noticeable
enhancement of the MO response in the near ultraviolet (UV) region
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 137
and significant potentials for their practical application as a storage
media. The MO properties of the Co/Pt [1–6] and Fe/Au [7–13] MLF
have been widely investigated experimentally and theoretically. The
experimentally observed unusual MO response is attributed to the
direct orbital hybridization between Pt(Au) and Co(Fe) atoms: the spin
magnetization of the magnetic Fe(Co) atoms is transferred to the
nonmagnetic Pt(Au) atoms and the stronger spin-orbit coupling of
the heavy Pt(Au) atoms is transmitted to the Fe(Co) atoms [14].
However, in spite of a huge number of publications and of some
attempts to determine the MO properties of the ‘magnetic’ Pt, for
example, undertaken by Sato and co-workers by analyzing the MO
spectra of FexPt1 − x alloys [15], the MO properties of the ‘pure’ spin-
polarized Pt and Au sublayers have not been yet confirmed.
For the correct interpretation of the experimental MO data, the
actual MLF structure should be known. An undertaken theoretical
attempt to interpret the experimental MO data for the Co/Pt MLF
had no success without taking into account the interfacial regions
[13]. Some quantitative agreement between the experimental and
modelled Kerr rotation spectra was achieved by Weller and cowork-
ers [1] for the Co/Pd MLF by solving the equations of the electro-
magnetic wave theory for the model, which considers also interfacial
region between pure components. Nevertheless, the similar approach
for the Co/Pt MLF failed partly owing to the irrelevant input data.
The origin for the discrepancy between experimental and simulated
data may originate from an inadequate model for the crystalline
structure, and improper use of the optical and MO constants for the
constituent sublayers, different from the real ones.
It is also well known that the MO response of the media is deter-
mined by their off-diagonal components of the dielectric function (DF)
(related to the MO properties) as well as by their diagonal compo-
nents of the DF (determining the optical properties). However, un-
like MO properties, the optical properties of the Co/Pt and Fe/Au
MLF are noticeably less investigated—only several publications
related to Co/Pt and Fe/Au MLF can be mentioned [5, 13, 15]. At
the same time, another possible explanation of such unusual MO
properties of the Fe/Au layered structures was also suggested by
Suzuki et al.: a new MO absorption appears due to formation of
quantum well states in very thin Fe sublayers [16]. If so, the for-
mation of these quantum well states should also found their mani-
festation in the optical properties of the Fe/Au MLF (while the first
one, probably, not).
3d-transition metal (TM) silicides have been receiving a great
attention in very-large-scale-integrated devices for interconnectors,
gates, and source contacts due to low resistivity, good thermal sta-
bility and small mismatch with Si substrate. Therefore, the ability
138 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
to grow silicides on semiconductor materials in a more controlled
manner has become a subject of increasingly importance. 3d-TM sili-
cide films are commonly fabricated by evaporation or sputtering of
the single 3d-TM layer onto Si substrate with a subsequent post-
annealing. From a thermodynamical point of view, such a 3d-TM
silicide formation is a consequence of decrease in the free energy of
the system through the solid-state reactions, until the thermally-sta-
ble end product is reached.
Apparently ‘new’ phenomena, in comparison with aforementioned
case can be observed in the 3d-TM/Si MLF structures: another con-
secution of phase appearance, the formation of metastable phases
which are not identified in the equilibrium phase diagram [17], an
extremely rapid growth (an ‘explosive’ reaction) [18], the formation
of amorphous interlayers by a reaction between the crystalline sub-
layers [19]. Solid-state reactions between a 3d-TM metal (for exam-
ple, Ni, Co, and Fe) and a Si substrate and 3d-TM/Si MLF during
annealing have been studied intensively [18, 20–27]. It was found
that the sequence of phase formation as well as the temperatures of
their appearance depend on many factors, such as beginning layered
structure, sublayer thicknesses, overall stoichiometry etc.
The employment of ion-beam mixing (IBM) creates additional per-
spectives for the silicide formation: it can lead to the interaction
between neighbouring layers by the energetic incident ions under
highly nonequilibrium conditions that the silicide formation can not
be achievable by the conventional equilibrium techniques. This com-
prises not only the energy to activate the interfacial interaction but
also the diffusion necessary to maintain the silicide growth. It was
reported that a rich variety of the structures induced by ion-beam
irradiation might be formed in 3d-TM films deposited onto Si sub-
strate [28–34].
Since the discovery of a strong antiferromagnetic (AF) interlayer
coupling in Fe/Si MLF, the reactive formation of interfaces between
Fe sublayers and the resultant interfacial structure appear to be
problems of intriguing complexity and a subject of comprehensive
study [35–43]. However, in spite of employment of many various
experimental tools for study of the stoichiometry and structure of
the interfacial regions in Fe/Si MLF (like soft-x-ray fluorescence and
near-edge x-ray-absorption fine-structure spectroscopy [42], x-ray
diffraction (XRD) [36], low-energy electron diffraction and Auger
electron spectroscopy [41, 43], and direct cross-sectional transmis-
sion electron microscopy observations [37]), the nature of the spon-
taneously formed spacer in Fe/Si MLF is still open.
The ability to predict a phase formation sequence and phase
decomposition during reactive deposition, solid-state reaction and
ion-beam mixing in terms of the effective-heat-of-formation model
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 139
was illustrated by Pretorius et al. [44]. Nevertheless, in practice, in
order to answer the question ‘What product of the solid state reaction
appears in the interfacial region of layered structures?’ an experi-
mental tools sensitive to the local environment like nuclear magnet-
ic resonance (NMR) or Mössbauer spectroscopies, in addition to the
standard structural-analysis methods such as XRD or transmission-
electron microscopy (TEM), should be employed. However, some of
these local methods may have some constraints (for example, an
existence of the nuclear magnetic moment for NMR) and cannot be
employed for the all systems.
It is well known that both optical and MO properties of metals
depend strongly on their electron energy structures which are cor-
related with the atomic and magnetic order. The spontaneous, ther-
mally or IBM induced interdiffusion between 3d-TM and Si layers in
the 3d-TM/Si MLF should change the chemical and atomic order in
the reactive zone and also decrease the thickness of 3d-TM sublay-
ers (and hence the MO response from the layered system). The skin-
penetration depth for most of the metals in the visible range of spec-
tra is about 20–30 nm. This means that, for the MLF whose indi-
vidual sublayer thickness is about of nanometres, the optical
response carries out the information on tens of sublayers.
Evidently, the real structures and magnetic properties of the as-
deposited and/or reacted MLF may be verified by a comparison
between the experimental and computer-simulated optical and MO
data, based on an appropriate model of the layered structure and the
properties of the constituent sublayers.
Thus, it seems attractive to show the potential of noncontact and
non-destructive spectroscopic ellipsometry (SE) and MO spectroscopy
for in situ study of the peculiarities of the MO properties of 3d-
TM/NM MLF, spontaneous, thermally or IBM induced solid-state
reactions in the 3d-TM/Si MLF as well as for the investigation of
the stoichiometry and properties of the interfacial regions which
provide the AF coupling in Fe/Si MLF.
EXPERIMENTAL AND SIMULATION DETAILS
A. Experimental Procedure
The 3d-TM/NM and 3d-TM/Si MLF of different nominal overall sto-
ichiometry, individual sublayer thicknesses and number of bilayer
repetitions were prepared onto glass and single-crystalline Si-wafer
substrates kept at room temperature (RT) by the computer-controlled
double-pair target face-to-face sputtering technique. The basic pres-
sure was about 1×10−6 Torr, an Ar pressure during the film deposi-
tion did not exceed 5×10−4 Torr, deposition rate was about 0.1 nm/s.
The parameters of the prepared MLF are shown in Tables 1 and 2.
The optical simulations need the knowledge of the optical and MO
properties of the constituent sublayers of the MLF (as input param-
eters for simulation). Therefore, film and bulk samples of pure NM,
3d-TM, Si as well as of nearly equiatomic 3d-TM/NM alloys and sev-
eral 3d-TM-silicides films were additionally fabricated in the similar
deposition conditions (for the film samples) and their DF were deter-
mined. It should be noted here that the films of 3d-TM silicides were
prepared also in crystalline and amorphous phases by using flash
evaporation onto heated and cooled substrates, respectively.
The structural characterization of the prepared MLF and film
samples was performed by using Θ–2Θ high-angle x-ray diffraction
(HAXRD) and low-angle x-ray diffraction (LAXRD) with CuKα and
CoKα radiation.
The optical properties (the real and imaginary parts of the complex
refractive index, N
∼ = n − ik) of the samples were measured at RT in a
spectral range of 260–1130 nm (4.7–1.1 eV) at a fixed incidence angle
of 73° by the polarimetric Beattie technique [45]. The obtained values
of n and k were used for calculating the spectral dependence of the
real (ε1) and imaginary (ε2) parts of the diagonal components of the DF
tensor and also of the optical conductivity1 2,xx yy zz iε = ε = ε = ε − ε
140 YuY. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
TABLE 1. The parameters of the investigated 3d-TM/NM MLF.
S
am
p
le
N
o.
Nominal MLF
formula
N
u
m
be
rs
of
b
il
ay
er
s
T
op
l
ay
er
Buffer
layer
(nm)
S
u
bs
tr
at
e
Nominal
overall MLF
composition
1 3.8 nm Co/1.34 nm Pt 50 Pt glass Co0.24Pt0.76
2 4.6 nm Co/1.36 nm Pt 50 Pt glass Co0.27Pt0.73
3 0.7 nm Co/1.25 nm Pt 44 Pt glass Co0.38Pt0.62
4 0.9 nm Co/1.44 nm Pt 40 Pt glass Co0.41Pt0.59
5 1.9 nm Co/1.43 nm Pt 33 Pt glass Co0.59Pt0.41
6 3.0 nm Fe/1.0 nm Au 20 Au Au, 20 glass Fe0.81Au0.19
7 3.0 nm Fe/2.0 nm Au 20 Au Au, 20 glass Fe0.68Au0.32
8 3.0 nm Fe/2.5 nm Au 20 Au Au, 20 glass Fe0.63Au0.37
9 3.0 nm Fe/3.0 nm Au 20 Au Au, 20 glass Fe0.59Au0.41
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 141
T
A
B
L
E
2
.
P
ar
am
et
er
s
of
t
h
e
p
re
p
ar
ed
3
d
-T
M
/S
i
M
L
F
.
Sample No.
N
om
in
al
M
L
F
f
or
m
u
la
N
om
in
al
ov
er
al
l
M
L
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st
oi
ch
io
m
et
ry
N
u
m
be
rs
of
b
il
ay
er
re
p
et
it
io
n
s
Top layer
Substrate
Ion-beam
treatment
T
em
p
er
at
u
re
o
f
h
ea
t
tr
ea
tm
en
t
(K
)
1
0
3
.0
n
m
N
i/
2
.6
9
n
m
S
i
N
i 0
.6
7
S
i 0
.3
3
4
0
N
i
S
i
+
−
1
1
3
.0
n
m
N
i/
5
.3
7
n
m
S
i
N
i 0
.5
0
S
i 0
.5
0
5
0
N
i
S
i
+
4
7
3
,
6
7
3
,
1
0
7
3
1
2
3
.0
n
m
N
i/
1
0
.7
n
m
S
i
N
i 0
.3
3
S
i 0
.6
7
2
2
N
i
S
i
+
4
7
3
,
6
7
3
,
1
0
7
3
1
3
3
.0
n
m
N
i/
1
0
.6
n
m
S
i
C
o
0
.3
3
S
i 0
.6
7
2
0
C
o
S
i
−
6
7
3
,
8
7
3
,
9
7
3
,
1
0
7
3
1
4
3
.0
n
m
F
e/
1
.0
n
m
S
i
F
e 0
.8
4
S
i 0
.1
6
5
0
F
e
g
la
ss
−
−
1
5
3
.0
n
m
F
e/
1
.3
n
m
S
i
F
e 0
.8
0
S
i 0
.2
0
5
0
F
e
g
la
ss
−
−
1
6
3
.0
n
m
F
e/
1
.5
n
m
S
i
F
e 0
.7
7
S
i 0
.2
3
5
0
F
e
g
la
ss
−
−
1
7
3
.0
n
m
F
e/
1
.8
n
m
S
i
F
e 0
.7
4
S
i 0
.2
6
5
0
F
e
g
la
ss
−
−
1
8
3
.0
n
m
F
e/
2
.0
n
m
S
i
F
e 0
.7
2
S
i 0
.2
8
5
0
F
e
g
la
ss
+
7
7
3
1
9
3
.0
n
m
F
e/
2
.2
n
m
S
i
F
e 0
.7
0
S
i 0
.3
0
5
0
F
e
g
la
ss
+
−
2
0
0
.3
n
m
F
e/
0
.5
n
m
S
i
F
e 0
.5
0
S
i 0
.5
0
1
2
0
F
e
g
la
ss
−
6
6
8
,
7
4
8
,
8
5
0
142 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
(OC, σ) by using the expressions: ε1 = n2 − k2, ε2 = 2nk, and
where ω is the angular frequency of light.
The MO equatorial Kerr effect (EKE) of the samples was measured at
RT by the dynamical method using the p-plane polarized light at two
angles of incidence (66 and 75°) in a spectral range of 260–1130 nm
(4.7–1.1 eV) and in an AC saturation magnetic field. The EKE value,
δp = ΔI/Io, is the relative change in intensity of the reflected light,
caused by the magnetization of the sample in an external magnetic
field directed transversely to the plane of the light incidence. The real
(ε′2) and imaginary (ε′1) parts of the off-diagonal components of the DF
( ) for the investigated samples were deter-
mined by using the experimental results of the optical study and the
MO measurements at two angles of incidence.
In-plane magnetization loops, M(H), for the investigated MLF
were measured by using a vibrating sample magnetometer (VSM).
FMR spectroscopy at RT and higher temperatures was also employed
for the magnetic study of the MLF.
After, the structural and physical properties of the as-deposited
3d-TM/Si MLF had been investigated, the MLF were ion-beam mixed
in a high vacuum (∼ 1×10−6 Torr) by Ar+ ions directed normally to the
film surface at the following conditions: an ion energy of 80 keV, an
ion flux of 1.5×10−6 A/cm2, and an ion dose of 1.5×1016 Ar+/cm2.
After mixing all the investigations were repeated.
Additionally to ion-beam treatment, some of the 3d-TM/Si MLFs
were annealed at different temperatures in order to induce the solid-
state reactions in it.
B. Simulation Details
The theoretical simulations of δp, σ and ε1 spectra for various MLF
were performed by solving exactly a multireflection problem by
using the scattering matrix approach [46], assuming either ‘sharp’
(ideal) interfaces resulting in rectangular depth profiles of the com-
ponents or ‘mixed’ (alloy-like) interfaces of variable thickness
between pure sublayers. The number of the constituent sublayers,
their nominal thickness and optical properties, and the angle of inci-
dence were the input parameters for the simulation.
It is clear that for the case of the mixed interfaces in the A/B
MLF, the transition from the A to B sublayer encounters a transi-
tional region where the AxB1−x alloy concentration is gradually changed
from a A-rich AxB1 − x alloy to a B-rich AxB1 − x alloy through the
equiatomic A–B region. More accurately, such an interfacial region
1 2,xy yx i i′ ′ ′ ′ε = −ε = ε ε = ε − ε
2( ) ,
4
ε ωσ ω =
π
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 143
probably can be expressed by a set of AxB1 − x alloy planes of differ-
ent compositions.
On the other hand, the thickness of this interfacial region cannot
be larger than a half of the bilayer period, and usually does not
exceed 1–2 nm, or 3–7 interatomic distances.
Additionally, the alloys of one or two monolayers’ thick probably
have no significant physical meaning for the relevant properties.
Therefore, the equiatomic A–B alloy is considered as an idealized
approximation representing the actual interface structure and sim-
plifying the simulation of the optical and MO properties of the A/B
MLF with mixed interfaces.
The complex DF for a magnetic medium magnetized along z-axis
with three-fold or higher symmetry about z-axis has the following
form
where, in general, the diagonal and off-diagonal terms are complex.
Introducing the complex Voigt parameter
and assuming that, for polycrystalline materials,
and we obtain
For a magnetically ordered medium in a magnetic field, the complex
refractive indices for the left (−)- and right (+)-circularly polarized
light can be defined as
while, for a nonmagnetic medium, this expression can be trans-
formed into
(5)= ε = ε − ε = − = − +2 2 2 2
1 2 ( ) ( ) 2 .xxN i n ik n k i nk
(4)2 (1 ),xx xy xxN i Q± = ε ± ε = ε ∓
(3)
1 0
1 0 .
0 0 1
xx
iQ
iQ
⎛ ⎞−
⎜ ⎟
ε = ε ⎜ ⎟
⎜ ⎟
⎝ ⎠
1 2,Q Q iQ= −,xy xxi Qε = ε
,xx yy zzε = ε = ε
(2),xy
xx
i
Q
ε
=
ε
(1)
0
0 ,
0 0
xx xy
xy yy
zz
ε ε⎛ ⎞
⎜ ⎟ε = −ε ε⎜ ⎟
⎜ ⎟ε⎝ ⎠
ε
144 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
C. Optical Properties of the MLF
Let us consider the MLF consisting of 1, 2, 3, …, j, …, m parallel,
isotropic and homogeneous layers, which are put between a semi-
infinite ambient medium (0) and a substrate (m + 1). The complex
refractive indices of the medium and substrate are and ,
respectively. Let E+(z) and E−(z) are the complex amplitudes of the
electromagnetic wave, which propagates forward and back in an
arbitrary plane z. E for different planes z′ and z′′ must be connect-
ed by the reorganization
or, in a shorter way, Eq. (6) can be rewritten as
E(z+) = SE(z′′), (7)
where S is the so-called scattering matrix
The scattering matrix S for such a MLF can be expressed as a
result of the multiplication of the reflection and phase matrices, I
and F, respectively, for each boundary and layer
S = I01F1I12F2...Ij(j + 1)F(j + 1)F(m + 1). (9)
The reflection matrix Ij(j +1) describes the reflection between j-th and
(j+1)-th adjacent layers,
where the Fresnel coefficients of reflection and transmission
between j and j+1 boundaries, Rj(j+ 1) and Tj(j+1), respectively, are cal-
culated for the p- and s-polarizations by using the complex refrac-
tion index for j-th layer,
and
(11)1 1
( 1) 2 2
1 1
2
,j j jp
j j
j j j j
N N A
T
N A N A
+ +
+
+ +
=
+
2 2
1 1
( 1) 2 2
1 1
,j j j jp
j j
j j j j
N A N A
R
N A N A
+ +
+
+ +
−
=
+
:j j jN n ik= −
(10)( 1)
( 1)
( 1)( 1)
11
,
1
j j
j j
j jj j
R
I
RT
+
+
++
⎛ ⎞
= ⎜ ⎟
⎝ ⎠
(8)11 12
21 22
.
S S
S
S S
⎛ ⎞
= ⎜ ⎟
⎝ ⎠
(6)11 12
21 22
( ) ( )
,
( ) ( )
S SE z E z
S SE z E z
+ +
− −
⎛ ⎞ ⎛ ⎞′ ′′⎛ ⎞
=⎜ ⎟ ⎜ ⎟⎜ ⎟ ′′⎝ ⎠⎝ ⎠ ⎝ ⎠
+1mN0N
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 145
where and ϕ is the angle of incidence.
The phase matrix Fj for the j-th layer can be defined as
where dj is the thickness of the j-th sublayer, and
λ is the light wavelength. Thus, it is clear that the knowledge about
the optical constants of each layer, the thickness and the angle of
incidence are enough for calculating the resultant scattering matrix
for the whole MLF.
After matrix S being calculated, the ellipsometric angles, ψ and
Δ, for the whole MLF (as if the material is actually homogeneous)
could be obtained by using the main equation of ellipsometry
While the ellipsometric angles are determined by using Eq. (14), the
effective optical constants, neff and keff, for the whole MLF can be
calculated from the equations for the optical invariants
and
D. Magnetooptical Properties of the MLF
According to Eq. (4), the complex refractive indices of each layer for
the right- and left-circularly polarized light can be defined as
(17)2 (1 ),j xxj jN Q+ = ε −
(16)2 2
2( ) ( ) ( ) 2
cos2 sin2 sin
2 2sin tan .
(1 sin2 cos )eff eff effn k
⎡ ⎤ψ ψ Δε = = ϕ ϕ ⎢ ⎥− ψ Δ⎣ ⎦
(15)
2 2 2
2 2 2
1( ) ( ) ( ) 2
cos 2 sin 2 sin
sin 1 tan ,
(1 sin2 cos )eff eff effn k
⎡ ⎤ψ − ψ Δε = − = ϕ + ϕ⎢ ⎥− ψ Δ⎣ ⎦
(14)21 11
11 21
tan .
p s
i
p s
S S
e
S S
Δψ ⋅ =
4
2 cos ,j
j j
d
N
π
δ = ϕ
λ
(13)
0
,
0
j
j
i
j i
e
F
e
δ
− δ
⎛ ⎞
= ⎜ ⎟⎜ ⎟⎝ ⎠
2 sinj jA N= − ϕ
(12)1
( 1)
1
2
,js
j j
j j
A
T
A A
+
+
+
=
+
1
( 1)
1
,j js
j j
j j
A A
R
A A
+
+
+
−
=
+
146 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
Using the same formalism, which was employed for the determina-
tion of the effective optical constants for the whole MLF, and Eqs.
(17) and (18), the effective complex refractive indices for the left-
and right-circularly polarized light can be determined, and then the
effective diagonal and off-diagonal components of the DF can be
obtained:
The transverse or equatorial Kerr effect for the whole MLF can be
expressed as [47]:
where
A = ε2(eff)(2ε1(eff)cos
2ϕ − 1),
B = (ε2
2(eff) − ε2
1(eff))cos
2ϕ + ε1(eff) − sin2ϕ.
RESULTS AND DISCUSSION
A. MO and Optical Properties of Noble Metal/3d-TM Multilayers
As an example, the HAXRD and LAXRD spectra for the Fe/Au MLF
(sample No. 7) are shown in Fig. 1. Several satellites are clearly seen
in the LAXRD spectrum indicating well-layered structure of the
Fe/Au MLF. The presence of a well-ordered layered structure is also
supported by the presence of several Bragg satellites in the HAXRD
(23)1( ) 2( )
p 2 2 2 2
2sin2 ,eff eff
′ ′ε ε⎛ ⎞
δ = ϕ +⎜ ⎟+ +⎝ ⎠
A B
A B A B
(22)
2 2
( ) ( )
1( ) 2( ) .
2
eff eff
eff eff
N N
i + −−
′ ′ε − ε =
(21)( ) ( ) ,xy eff xx eff effi Qε = − ε
(20)
2 2
( ) ( )
( ) 2 2
( ) ( )
,eff eff
eff
eff eff
N N
Q
N N
+ −
+ −
−
=
+
(19)
2 2
( ) ( )
( ) ,
2
eff eff
xx eff
N N+ −+
ε =
(18)2 (1 ).j xxj jN Q− = ε +
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 147
spectrum located symmetrically around main diffraction peak,
which originates from the buffer layer. The calculation of the actu-
al bilayer period of the Fe/Au MLF by using LAXRD as well as
HAXRD satellite peak positions reveals the consistent results. An
increase of the Au sublayer thickness causes the decrease in interval
between satellites peaks in the LAXRD spectra and some shift of the
main diffraction maximum to the high-angle side of the HAXRD
spectra. From the HAXRD measurements a pronounced (111)-tex-
ture for the as-deposited Co/Pt MLF was inferred.
The in-plane magnetization hysteresis loops, M(H), for the Fe/Au
MLF taken at RT indicate their magnetically soft behaviour with a
coercivity of about 10–16 Oe and show the presence of the super-
paramagnetic behaviour in a high-field region. The superparamag-
netic contribution was also observed for the field dependences of the
EKE. Both these factors allow us to suppose that two magnetic phas-
es are present in the Fe/Au MLF.
The measured optical properties of the Fe/Au MLF together with
Fig. 1. HAXRD and LAXRD (see inset) spectra for the Fe/Au MLF (sam-
ple No. 7).
148 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
those of Fe, Au and nearly equiatomic Fe0.59Au0.41 alloy films are
shown in Fig. 2. The optical properties of gold are well known [48]
and are explained by first-principles calculations [49]. The experi-
mentally obtained σ( ω) and ε1( ω) spectra for the Au-film nicely
reproduce known literature results, namely a rapid break in the OC
near 2.5 eV (which is related to the threshold of the interband
absorption) and pure intraband absorption below ω < 2 eV. The
optical properties of the Fe-film are also in an agreement with
known experimental [50] and theoretical [51] results, exhibiting a
wide interband absorption peak in the OC spectrum near 2.4 eV. As
a whole, the optical properties of the Fe/Au MLF manifest the opti-
cal properties of both Fe and Au. Since, however, the 2.4 eV peak of
Fe is located practically at the same energy of deep minimum of the
OC spectrum of Au, the resulting σ( ω) spectra of the Fe/Au MLF
are free of any prominent features: a broad plateau of the σ( ω) is
seen for the 2–5 eV energy range, while for ω < 1.5 eV energy
region intraband absorption becomes dominant. The optical proper-
ties of Fe0.59Au0.41 alloy films in the visible region of spectra are in
between of pure Fe and Au ones being rather similar to those of the
Fe/Au MLFs.
The σ( ω) and ε1( ω) spectra of pure Co and Pt films, as well as
of Co/Pt MLFs in the 0.5 < ω < 5.0 energy range do not show any
significant peculiarity and practically monotonously increases in
Fig. 2. The experimental (a) OC and (b) ε1 spectra for the Fe/Au MLF
together with those for Fe, Au and Fe0.59Au0.41 alloy films. The similar des-
ignations of the curves are used in panels (a) and (b).
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 149
absolute value with decrease in photon energy. The only regularity
can be mentioned: the σ( ω) and ε1( ω) values for Pt film are always
larger than the corresponding spectra of the Co-film, with σ( ω) and
ε1( ω) spectra for the Co/Pt MLFs in between of them (not shown).
The experimental EKE spectra for Fe/Au MLFs as well as pure Fe
and Fe0.59Au0.41 alloy films are shown in Fig. 3.
Since the differences between the experimental and simulated
δp( ω), σ( ω) and ε1( ω) spectra turn out to be nearly the same for
all the investigated Fe/Au MLF, we restrict our discussions on the
sample No. 9 (see Figs. 4 and 5). Noticeable disagreements between
the experimental and simulated δp( ω), σ( ω) and ε1( ω) spectra
obtained for the model of nominal structure of Fe/Au MLF and
abrupt interfaces between pure metal sublayers is a clear indication
of bad approach used to model the MLF. Simultaneously the best
correspondence between experimental and simulated σ( ω) and ε1( ω)
spectra in the whole spectral range was obtained for the MLF model
of the sample No. 9, which supposes the formation of the alloyed
interfacial region of tint(9) = 1.8 nm in thickness between Fe and Au
sublayers (see Fig. 4). The increase the thickness of the interfacial
region in the model results in even worse fitting. The interfacial
region was modelled by using the optical constants of the ferromag-
netic Fe0.59Au0.41 alloy films. Nearly, the same thicknesses of the
alloyed interfacial regions provide (tint(7) = 1.7 nm; tint(8) = 1.9 nm)
also the best fit of the simulations for other Fe/Au MLFs, sample
Fig. 3. EKE spectra for the Fe/Au MLF taken at RT and the angle of inci-
dence of 66°. The EKE spectra for pure Fe (with a scaling factor of 0.5)
and Fe0.59Au0.41 alloy films are shown for the comparison.
150 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
Fig. 4. Experimental (open triangles) and simulated (lines) (a) σ( ω) and (b)
ε1( ω) spectra for the (3.0 nm Fe/3.0 nm Au)20 MLF obtained for the model
of the nominal MLF structure (solid lines) and for the case of mixed inter-
face of 1.8 nm in thickness between Fe and Au layers (dashed lines). Inset
in panel (b) shows an enlarged view of the high-energy part of the ε1( ω)
spectra.
Fig. 5. Experimental (symbols) and simulated (lines) EKE spectra for the
(3.0 Fe/3.0 nm Au)20 MLF obtained for the model of the nominal MLF
structure and for the case of mixed interface of 1.8 nm in thickness
between Fe and Au layers. The experimental EKE spectrum for Fe-film is
shown by open diamonds for the comparison.
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 151
Nos. 7 and 8. It should be reminded here, that in optical simulations
we used the optical constants of ‘thick’ (∼ 100 nm or more) Fe, Au
and Fe0.59Au0.41 films and obtained reasonable correspondence
between experiment and simulations in the whole investigated spec-
tral range. This means that the optical properties (and hence the
electronic structures) of the ‘thin’ (∼ 1–3 nm in thickness) Fe and Au
layers in Fe/Au MLF are close to those of ‘bulk’ Fe and Au; no
‘quantum well states’ were detected in the investigated Fe/Au MLF
in such a way.
It is seen (see Fig. 3) that the experimental EKE spectra for
Fe/Au MLF are characterized by two peculiarities (or peaks) which
are located at ∼ 2.7–2.8 and ∼ 4 eV. At the same time, the EKE spec-
trum for pure Fe-film exhibits a definite maximum at ∼ 1.7 eV. The
comparison between the experimental and simulated EKE spectra for
the Fe/Au MLF allow us to conclude that the low-energy peak in the
EKE of the Fe/Au MLF originates from Fe-sublayers and its blue-
shift by about 1 eV is caused by the interplay of the optical con-
stants in the Fe/Au MLF. Indeed, the modelled EKE spectrum
obtained for the model of the nominal Fe/Au MLF structure and
nonmagnetic Au sublayers, exhibits a strong peak which is located
at practically the same energies as the experimental one (see Fig. 5).
At the same time such a simulation reveals that the experimental
EKE spectrum exceeds the modelled one for ω > 3.0 eV. The simu-
lation of the EKE spectra for the Fe/Au MLF model with alloyed
interfacial region of the same thickness (which allowed to obtain
best resemblance of the experimental and simulated optical spectra),
reveals perfect fit to the experimental data in low-energy region. As
input parameters for alloyed interfacial regions in this model of
Fe/Au MLF, the MO and optical properties of the ferromagnetic
Fe0.59Au0.41 alloy film were used. However, for ω > 2.5 eV energy
range, the experimental MO response still exceeds the modelled one.
Thus, it is clear that, in addition to ferromagnetic Fe and Fe0.59Au0.41
sublayers, the presence of the third source in the resulting MO
response of the Fe/Au MLF should be supposed. Moreover, this
source may be spin-polarized Au sublayers [52].
In order to determine the MO properties (i.e. the off-diagonal com-
ponents of the DF tensor) of spin-polarized Au layers, the following
approach was employed. All the experimental responses which
exceed the modelled one (for alloyed interface model) one, i.e.,
Δ( ω) = δp_exp.( ω) − δp_mod.( ω) was determined at two angles of inci-
dence (i. e., at ϕ = 66 and 75°) and referred to as the spin-polarized
Au sublayers. Having known the optical constants of Au layers and
the Δ( ω) at two angle of incidence, the absorptive ( ω)2ε′2 and dis-
persive ( ω)2ε′1 parts of the off-diagonal components of the DF for
spin-polarized Au sublayers were determined by using the algorithm
152 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
Fig. 6. Experimental (symbols) and simulated (lines) EKE spectra for the
(0.9 nm Co/1.44 nm Pt)40 MLF obtained for the model of the nominal MLF
structure (solid line) and for the case of mixed interface of 0.9 nm in thick-
ness between Co and Pt layers (dashed line). The EKE spectra for pure Co
and Co0.51Pt0.49 alloy films are shown for the comparison.
Fig. 7. Absorptive parts of the off-diagonal components of the DF for spin-
polarized Pt (solid line, left scale) and Au (dashed line, right scale) layers.
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 153
of Krinchik [47]. Practically the same regularities between experi-
mental and simulated EKE spectra were also observed for Co/Pt
MLF (see Fig. 6). The detailed results related to Co/Pt MLF can be
found elsewhere [53]. Figure 7 shows the ( ω)2ε′2 spectra for Pt and
Au layers obtained in such a way. Both these spectra manifest a
prominent peak near 4 eV (while the magnitude of Au-related peak
is much smaller) and this fact explains large experimental MO
responses in the UV region of spectra observed for Co/Pt and Au/Fe
MLFs.
B. Interlayer Coupling in the Fe/Si MLF
HAXRD spectra of the all as-deposited Fe/Si MLFs (sample Nos.
14–19) look rather similar to each other with small differences in
main diffraction peak position. As an example, one of them (related
to the sample No. 18) is shown in Fig. 8. The asymmetry of the
satellite peak with respect to the main peak in the HAXRD spectra
for the Fe/Si MLF has been also observed earlier by Chaiken et al.
[37] and Fullerton et al., and explained by the presence of interdif-
fused interfaces [36]. No peak related to Si or other elements was
Fig. 8. HAXRD and LAXRD (see inset) spectra for the Fe/Si MLF (sample
No. 18) in the as-deposited state (solid circles and 1) and after ion-beam
treatment (open triangles and 2). Arrows show the position of the most
intense diffraction lines for Fe and (from left to right) for crystalline sili-
cides of Fe2Si, ε-FeSi, Fe5Si3 and Fe3Si, respectively.
154 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
found. The Fe/Si MLF manifests a crystal coherence length, ξ, esti-
mated from the FWHM of the main diffraction peak, of about 7 nm.
This implies that there is no amorphous Si left in our samples and
the interfacial reaction between Si and Fe has led to a crystalline
multilayer structure. The main diffraction peak is located near the
(110)Fe peak location as well as near the positions of the most
intense diffraction lines for several stable at RT iron silicides (see
Fig. 8). Therefore, having only the HAXRD data it is hard to con-
clude definitely what structure the as-deposited Fe/Si MLF has. At
the same time, the LAXRD patterns for the as-deposited Fe/Si MLF
confirm their layered structure (see inset in Fig. 8).
The prepared Fe/Si MLFs exhibit the fairly strong AF coupling,
as already reported [35, 37, 43]. The saturation field Hs for in-plane
hysteresis loops of the (3.0 nm Fe/m Si)50 MLFs, where m is the Si-
sublayer thickness, rapidly increases from 0.08 kOe for m = 1.0 nm
reaching the peak value of Hs ∼ 12–14 kOe at m = 1.3 nm, and then
decreases down to 0.2 kOe for m = 2.2 nm, indicating a strong AF
exchange coupling.
As aforementioned for the purpose of simulations, the optical pro-
perties of nominal and possible candidates for the constituent sub-
layers of Fe/Si MLF, i.e., of Fe, Si, and amorphous FeSi2 films as
well as α-FeSi2, β-FeSi2, and ε-FeSi bulks, were measured (not
shown). It should be mentioned here that all the examined candi-
dates for the spacer (except, naturally, Fe) show a large and positive
ε1 in the IR region of spectra and a relatively small σ, in other
words, exhibit a semiconductor-like behaviour. Knowing the optical
characteristics of these materials, we can calculate the MO and opti-
cal properties of the Fe/Si MLF and compare the simulated spectra
with the experimentally determined ones.
Since the observed regularity in the behaviour of the experimental
and simulated δp( ω), σ( ω) and ε1( ω) spectra turn out to be nearly the
same for all the investigated Fe/Si MLF, we restrict our discussions
on sample No. 18 (see Fig. 9). First of all, two main results should be
noted here; (i) the simulation with the nominal Fe/Si MLF structure
predicts a prominent enhancement of the MO response in the near-IR
region with respect to that of pure Fe; (ii) a decisive disagreement
between the experimental and simulated δp( ω) and optical spectra is
observed for the case of the nominal structure of MLF in the model.
The enhancement of the MO response in the modelled EKE spec-
trum can be explained by an interplay between the optical constants
of Fe and Si in this spectral range [see expression (23)]. The decisive
disagreement between the experimental and the simulated (with the
nominal Fe/Si MLF structure) δp( ω), σ( ω) and ε1( ω) spectra (see
Fig. 9) suggests a presence of another than nominal layered struc-
ture in our as-deposited Fe/Si MLF.
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 155
Therefore, next step of simulations employed the Fe/Si MLF
model, which supposes that all the Si sublayers were completely con-
sumed for the formation of iron silicide of various stoichiometries.
It should be reminded here that the spacer should be nonmagnetic.
Therefore, the stoichiometry of the possible silicides as a spacer, i.e.
FexSi1 − x, should be searched in the x≤0.5 region. The thicknesses of
the residual Fe sublayers and as well as of newly formed iron sili-
cide sublayers for these models were calculated with use of the tab-
ulated densities of crystalline iron silicides. The δp( ω), σ( ω) and
ε1( ω) spectra for different models of the Fe/Si MLF are shown in
Fig. 9. All these spectra appear to be completely different in both
intensity and shape from the corresponding experimental ones.
Fig. 9. Experimental (symbols) and simulated (lines) (a) δp( ω) (b) σ( ω) and
(c) ε1( ω) spectra for (3.0 nm Fe/1.8 nm Si)50 MLF. Various kinds of spac-
ers were used in the simulations: (dashed lines) nominal MLF structure and
amorphous Si, (dotted lines) amorphous FeSi2, (dashed-dotted lines) ε-FeSi.
Modelled spectra with use of extracted FeSi spacer are shown by solid lines.
156 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
Thus, such a decisive disagreement rules out the hypothesis of FeSi2
or ε-FeSi silicides as spontaneously formed nonmagnetic spacers
between Fe sublayers.
Because of lack of the knowledge of the optical properties of other
iron silicides, we used another approach in order to determine the
optical properties of the interfacial regions. We assumed that the
experimentally observed optical properties of the Fe/Si MLF result
from those of the Fe layers (whose optical properties are known) and
of those of the hypothetical nonmagnetic spacers. Then, taking into
account the additive character of the contributions from different
phases to the DF of MLF, the optical properties of the spacer were
extracted in the framework of the effective medium approximation
for a spacer stoichiometry of FeSi. The correctness of such a proce-
dure was cross-checked by employing the extracted optical properties
of the spacer as input parameters in the reciprocal exact simulation
that should restore the measured optical properties of the Fe/Si MLF.
It is seen in Fig. 9, b and c that the simulated σ( ω) and ε1( ω) spec-
tra reproduce the experimental ones with a great resemblance.
In contrast to the cases based on the structural model with FeSi2
or ε-FeSi as the spacers, the above approach allows us to obtain a
significantly better correspondence in shape between experimental
and simulated EKE spectra (see Fig. 9, a). However, it should be
noted that the intensity of the modelled spectra is somewhat larger
than the experimental one. The better resemblance in the intensity
between experimental and simulated EKE spectra can be probably
obtained by a more correct estimation of the fraction of nonreacted
Fe in the actual Fe/Si MLF. The major finding is that the experi-
mentally extracted optical properties of the spacer with FeSi stoi-
chiometry exhibit rather similar energy dependence for all the exam-
ined Fe/Si MLF and possess a typical metallic behaviour (see Fig. 10)
in contrast to FeSi2 or ε-FeSi. Thus, such an approach leads us to
suggest that the nonmagnetic spacer in the Fe/Si MLF, providing an
AF coupling, is metallic with composition close to FeSi.
In order to understand the experimentally extracted optical prop-
erties of the spacer we calculated the electronic band structures of
the FeSi compound with B2 type of structure using a scalar-rela-
tivistic version of tight-binding linear muffin-tin-orbital method
within the local-spin-density approximation (LSDA). An atomic-
sphere approximation was used. The spin-orbit interactions were
included in the self-consistent iterations. For the exchange-correla-
tion effect, we used the LSDA expression of von Barth and Hedin
[54]. Once the self-consistent potential and charge were obtained,
the density-of-states curves and the optical conductivity spectra
were calculated using the linear-energy-tetrahedron method [55]
with a finer mesh of irreducible wedge.
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 157
Figure 10 compares the theoretical σ( ω) spectra for FeSi with the
extracted σ spectra of the spacer. Since the calculated and broadened
σ spectrum for FeSi resembles the experimentally extracted one
except the peak positions, we applied the real part of the self-ener-
gy correction (SEC) or λ-fitting [56] to match their energy positions.
It is seen in Fig. 10 that the broadened and SEC σ spectrum for FeSi
exhibits a noticeable resemblance to the experimentally extracted σ
spectrum for the spacers. Therefore, it can be concluded that the
metallic, nonmagnetic FeSi with a B2 structure is formed sponta-
neously in the Fe/Si MLF with relatively ‘thick’ sublayers.
Since such a spacer is spontaneously formed between Fe sublayers
of Fe/Si MLF, we tempted to fabricate pure iron-silicide with B2-
type of structure by choosing of proper Fe and Si sublayer thick-
nesses (sample No. 20, see Table 2). However, in spite of our expec-
tations, the optical properties of the as-deposited and all the
annealed Fe/Si MLF with ‘thin’ sublayers and overall composition of
Fe0.50Si0.50 drastically differ from those of the aforementioned sili-
cide spacer being rather similar to ε-FeSi ones. Even though the
XRD spectra for this Fe/Si MLF in the as-deposited state after all
steps of annealing indicate their amorphous structures, it can be
supposed that the short-range order in such films is close to ε-FeSi,
i.e., to B20 type.
Fig. 10. Experimental (solid triangles) OC spectrum for the ion-beam treat-
ed (3.0 nm Fe/2.0 nm Si)50 MLF together with calculated and broadened
(dashed line) and self-energy corrected OC (open circles) spectra.
158 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
C. Optical Study of 3d-TM-Silicides Formation
Unlike the Fe/Si MLF case (sample Nos. 14–19, see Fig. 8) there are
no any visible rings (peaks) in the HAXRD patterns for all the as-
deposited Ni/Si and Co/Si MLFs (samples 10–13) (not shown).
However, such amorphous-like structures are not homogeneous,
since the corresponding LAXRD patterns exhibit several well-
defined satellites, which indicate their good-layered structures (not
shown). Also unlike the Fe/Si MLFs, the in-plane and out-of-plane
magnetization hysteresis loops, M(H), for all the as-deposited Ni/Si
and Co/Si MLFs show the superparamagnetic behaviour. These
results can be understood if the noticeable intermixing of the Ni(Co)
with Si sublayers will be supposed. According to the results of
Fallon [57] and Babu [58], the superparamagnetic behaviour at RT
in co-deposited Co1−xSix and Ni1−xSix alloy films is observed for
x>0.40 and x>0.13, respectively. The magnetic data obtained by
VSM also corresponds to the results of the EKE measurements—no
MO response at RT was detected for all the as-deposited Ni/Si and
Co/Si MLFs. This allows us to assume that Ni and Co sublayers lost
their ferromagnetic order owing to their enrichment by Si at least
up to 13 and 40 at.%, respectively, and hence that the actual struc-
tures of the as-deposited MLFs are far from the nominal ones.
The shape of the simulated OC spectra of the Ni/Si and Co/Si
MLFs (for the case of nominal MLF structures) is dictated by very
intense absorption peak in OC spectrum of amorphous Si. All the
simulated OC spectra for the Ni/Si MLF (see Fig. 11 and also, for
Co/Si MLF, see Fig. 12) look rather similar each other in shape with
some difference in peak position: an increase in Si sublayer thick-
ness causes the red-shift of the maximum from ∼ 3.30 (for the sam-
ple No. 10) to ∼ 3.10 eV (for sample No. 12). The absence of even any
visible trace of the Si-related absorption peak in the experimental
OC spectra of the as-deposited Ni/Si MLF with overall stoichiome-
tries of Ni2Si and NiSi as well as of Co/Si MLF enables us to sup-
pose the lack (or a noticeable reduction) of the pure Si content in
such films due to the Si (and naturally the Ni(Co)) consumption for
the Ni(Co)-silicide formation. It is also seen that more or less rea-
sonable correspondence in the shape between the simulated and
experimental OC spectra is observed only for the Ni/Si MLF with the
thickest (among the investigated Ni/Si MLF) Si sublayers (see
Fig. 11, d). However, the magnitude of the modelled OC spectrum is
larger than that of the experimental one. Thus, we can conclude that
the employed MLF model, assuming the nominal MLF structures
with an abrupt interfaces between pure Ni(Co) and Si sublayers does
not describe adequately the actual structures of the as-deposited
MLFs.
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 159
Fortunately, unlike the case of the Fe/Si MLF, the OC spectra of
the equiatomic as well as Ni-rich and Co-rich silicides are known
from the literature [59] and from our measurements. All these spec-
tra exhibit well definite absorption peaks located at noticeably dif-
ferent energies (see Figs. 11, a and 12, a). Comparing the experi-
mental OC spectra for the as-deposited Ni/Si and Co/Si MLFs with
those of aforementioned silicides, rough conclusion on the struc-
tures of the as-deposited and treated Ni/Si and Co/Si MLF can be
Fig. 11. Experimental (symbols) and modelled (lines) OC spectra for the as-
deposited, ion-beam treated and annealed (b) (3.0 nm Ni/2.69 nm Si)40, (c)
(3.0 nm Ni/5.37 nm Si)50 and (d) (3.0 nm Ni/10.7 nm Si)22 MLFs. Solid lines
on panels (b)–(c) represent the modelled OC spectra obtained for nominal
MLF structures and shown with a scaling factors of 0.6, 1 and 1, respec-
tively. Dashed lines on panels (b) and (d) show the modelled OC spectra
obtained for the models with mixed interface (see text). Panel (a) shows the
literature OC spectra for the crystalline nickel silicides [59].
160 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
made. Thus, noting that the OC spectra for the as-deposited Ni/Si
MLFs (sample Nos. 10 and 11) have a peculiarities (or shoulders) at
∼ 2 eV where the intense peak in the OC spectrum for crystalline
equiatomic NiSi is located, the formation of the regions with the
short-range order close to that presented in the η-NiSi may be sup-
posed for such a MLF (see Fig. 11, a–c).
The agreement between the simulated and experimental OC spectra
of the as-deposited (3.0 nm Ni/10.7 nm Si)22 MLF is significantly
improved in spectral shape and magnitude if the complete consump-
tion of the Ni sublayers and hence a noticeable part of the Si sublay-
ers for the formation of nonferromagnetic Ni-silicides of NiSi and
Ni3Si stoichiometries is assumed. The nearest approach to the experi-
mental results was obtained for the model of this MLF with following
sequence of the layers: (4.3 nm NiSi/1.2 nm Ni3Si/4.7 nm Si/4.3 nm
NiSi)22 (see Fig. 11, d). As input parameters for Ni3Si and amorphous
NiSi, the literature results for crystalline Ni3Si [59] as well as our
experimental data for the as-deposited (3.0 nm Ni/5.37 nm Si)50 MLF
were used, since the latter one has an overall stoichiometry of NiSi
and its optical properties are very close to those of crystalline NiSi
(see Fig. 11, a and c). The spectral shape of the as-deposited Co/Si
Fig. 12. Experimental OC spectra for (a) crystalline Co2Si, CoSi and CoSi2
silicides and (b) for the (3.0 nm Co/10.6 nm Si)20 MLF in the as-deposited
state and after several steps of annealing. For the convenience of the obser-
vation, OC for bulk Co2Si is shifted downward by 7 units. Solid line on
panel (b) represents the simulated OC spectrum for the nominal structure
of the MLF shown with a scaling factor of 0.6.
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 161
MLF may be reasonably reproduced by the model, which supposes that
the actual structure contains the regions with the short-range order
close to Co2Si (60%), CoSi (30%), and Si (10%).
IBM of the samples Nos. 10, 12, 18 and 19 does not produce any
visible changes in the LAXRD spectra; HAXRD patterns for the
Ni/Si MLF still indicate their amorphous structures, while HAXRD
spectrum for the Fe/Si MLF is somewhat changed: main peak is
shifted to the high-angle side, and becomes narrower and more
intense (see Fig. 8). Again, because of several stable at RT iron-sili-
cides have the most intense diffraction lines at the angles where
main diffraction peak for the ion-beam treated Fe/Si MLF is locat-
ed, any confident conclusion on the structure produced by IBM can
be made on the basis of the HAXRD results.
However, the noticeable changes were observed in the OC spectra
of the Ni/Si and Fe/Si MLF (see Figs. 11 and 13). Furthermore, the
magnetic and MO measurements indicate that the IBM forms new
magnetically soft phase with a smaller magnetization (see Fig. 14).
The OC spectrum of the ion-beam mixed (3.0 nm Ni/2.69 nm Si)40
MLF shows a prominent enhancement in the magnitude for ω < 2.8
eV, clearly revealing new absorption peaks at ω ∼ 0.7 and 1.8 eV
(marked by arrows in Fig. 11, b). A comparison of the OC spectrum
Fig. 13. (a) σ( ω) and (b) ε1( ω) spectra for the as-deposited (solid circle)
and ion-beam mixed (open triangles) (3.0 nm Fe/2.0 nm Si)50 MLF. Solid
line in (a) shows the broadened and self-energy corrected theoretical σ( ω)
for Fe2Si silicide (B2 type of structure). The theoretical σ( ω) spectrum is
plotted with a scaling factor of 0.83.
162 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
with those of various crystalline Ni silicides allows us to assume
that the peak at ∼ 1.8 eV is probably related to the low-energy peak
in the OC spectrum of crystalline NiSi, while the 0.7 eV one origi-
nates from Ni2Si or, more probably, from Ni3Si. This supposition is
further supported by the comparison of the experimental OC spectra
with the simulated one made for the model with alloyed interfacial
region (see Fig. 11, b). In this model, the following periodic element
of the (3.0 nm Ni/2.69 nm Si)40 MLF was used: (2.1 nm Ni/0.2 nm
Ni3Si/3.3 nm NiSi/0.2 nm Ni3Si). As input parameters for simula-
tion the optical constants for crystalline Ni3Si [59] and as-deposited
Ni/Si MLF of NiSi stoichiometry were used. The prominent changes
in the OC spectra, induced by IBM, is also observed for the (3.9 nm
Ni/13.9 nm Si)22 MLF which can be interpreted in terms of a forma-
Fig. 14. (a) Magnetization hysteresis loops, (b) FMR and (c) EKE spectra
for the (3.0 nm Fe/2.0 nm Si)50 in the as-deposited state (solid circles),
after ion-beam mixing (open triangles).
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 163
tion of the structures with a short-range order close to the mixture
of Ni2Si and NiSi (compare the corresponding OC spectra in Fig. 11).
Contrary to the aforementioned Ni/Si MLF, IBM does not produce
any visible change in the OC spectrum of (3.0 nm Ni/5.37 nm Si)50
MLF with an overall stoichiometry of NiSi: the spectrum after IBM
(as well as as-deposited Ni/Si MLF) shows an absorption peak at
ω ∼ 2 eV. Such a peak is absent in the OC spectra of pure Ni and Si,
but is present in that of crystalline NiSi (see Fig. 11, a). Clevenger
and Thompson revealed the experimental and thermodynamical evi-
dences that the reaction phase selection in a polycrystalline
Ni/amorphous Si thin film is governed by the so-called ‘nucleation
model’: the formed silicide phase is one with the highest nucleation
rate or the smallest nucleation barrier [60]. Therefore, it can be
assumed that the nuclei of NiSi phase (for example, amorphous NiSi)
are spontaneously formed during the deposition of (3.0 nm
Ni/5.37 nm Si)50 MLF, and IBM does not produce new ones.
The stoichiometry of the ion-beam mixed layers can be also qual-
itatively estimated by comparing the experimentally determined
optical properties of Fe/Si MLF after the IBM with those of Fe–Si
alloys of various compositions. It is seen that the calculated (broad-
ened and self-energy corrected) OC spectrum for Fe2Si silicide (a B2
type of structure) presents a reasonable resemblance to the experi-
mental OC spectrum of Fe/Si MLF after the IBM in both shape and
location of the absorption peaks (see Fig. 13, a). The electronic ener-
gy band structures of Fe2Si silicide were calculated using a scalar-
relativistic version of atomic-sphere-approximation tight-binding
linear-muffin-tin-orbital method within the local-spin-density-
approximation [61]. Since the stoichiometry of Fe2Si alloy is not
appropriate for the equilibrium B2-type structure (because a half of
the Si sites should be unoccupied in this case), we assumed that a
vacancy is introduced in the formula unit, and 2 Fe atoms, 1 Si atom
and 1 vacancy form a Heusler-like alloy; i.e. a chain of Fe–Si–Fe-
vacancy is aligned along the (111) direction of the B2-type unit cell.
The resultant Bravais lattice is f.c.c. The details for calculation of
the optical properties and for use of the self-energy correction can
be found elsewhere [62].
According to the results of HAXRD study, an annealing of the
Ni/Si and Co/Si MLFs (sample Nos. 11–13) at 673 K leads to the
appearance of weak traces of the intermediate phases, i.e. of η-NiSi
as well as Co2Si and mainly CoSi, respectively. Next steps of anneal-
ing of the Co/Si MLF at 873 and 973 K cause the formation of the
CoSi phase, while annealing at 1073 K forms CoSi2 phase in Co/Si
MLF. An annealing at temperatures of 873 K and 1073 K of the
(3.0 nm Ni/5.37 nm Si)50 MLF does not cause any difference in the
HAXRD patterns. However, an annealing at 1073 K of the (3.0 nm
164 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
Ni/10.7 nm Si)22 MLF leads to appearance additionally of the only
(111) NiSi2 diffraction line. Thus, according to the HAXRD results,
the (3.0 nm Ni/5.37 nm Si)50 MLF is crystallized into the η-NiSi
phase, while the annealing at 1073 K of the (3.0 nm Ni/10.7 nm Si)22
MLF leads to the formation of a dual structure (a mixture of η-NiSi
and NiSi2) with a predominance of the η-phase. It should be men-
tioned here that the observed sequence of the Ni-silicide phases,
induced by the thermal annealing, in the investigated Ni/Si MLF
differs from those in the literatures: an annealing at 1073 K of the
Ni/Si layered structure usually leads to the NiSi2 phase [22, 24, 25].
Thermal annealing at different temperatures (above 473 K) of the
(3.0 nm Ni/5.37 nm Si)50 causes gradual changes in the optical prop-
erties towards those of the crystalline NiSi: each step of annealing
makes the interband absorption peak at ω ∼ 2 eV more evident. This
means that such a process illustrates an improvement in the crys-
tallinity of NiSi phase spontaneously formed during the film depo-
sition. Contrary to the HAXRD results, the evolution of OC spec-
trum, induced by the thermal annealing of the (3.0 nm Ni/10.7 nm
Si)22 MLF above 473 K, clearly indicates the formation of NiSi2
phase. The optical and HAXRD results might be correlated when we
take into account the fact that the skin depth for the visible region
is about 20 nm and also that the formation of NiSi2 phase takes place
mainly in the surface region of MLF, while the HAXRD response is
Fig. 15. Experimental (symbols) and simulated (solid lines) (a) OC and (b)
ε1( ω) spectra for the (3.0 nm Co/10.6 nm Si)20 MLF after annealing at
873 K. The simulated OC spectrum is plotted with SF of 0.66.
Optical and Magnetooptical Spectroscopy of the Nanostructural Films 165
made from the total volume of MLF.
The comparison of the experimental optical properties of the (3.0
nm Co/10.6 nm Si)20 MLF subjected to the annealing at 873 K allows
us to conclude that newly formed CoSi phase as well as residual Si
are main components of the Co/Si MLF (see Fig. 15). An annealing
of the Co/Si MLF at 1073 K causes the prominent changes in its
optical properties: the interband absorption peaks at 0.7 and
1.5–2 eV have disappeared, and instead of a broad peak at 3.2 eV,
two peaks at 2.75 and 3.6 eV have occurred in the OC spectrum of
this MLF (see Fig. 12). The comparison of the experimental σ spec-
trum of such an annealed Co/Si MLF with that of crystalline bulk
CoSi2 (see Figs. 12, a and b) indicates their perfect agreement.
Therefore, the conclusion on the formation of crystalline CoSi2 phase
in Co/Si MLF can be confidently made on the basis of only optical
data. The HAXRD spectrum of the Co/Si MLF annealed at 1073 K
is also changed drastically showing the formation of crystalline
CoSi2 phase.
SUMMARY
1. The real structures of the Fe/Au and Co/Pt MLFs were elucidated
on the basis of the comparison of their experimental and computer-
simulated optical properties. It was shown that all the investigated
Fe/Au and Co/Pt MLFs have alloyed interfacial regions between pure
components of about 1–2 nm in thickness. These regions noticeably
influence on the resulting MO properties of the MLF.
2. The off-diagonal components of the DF for the spin-polarized Au
and Pt sublayers in the Fe/Au and Co/Pt MLF were determined for
the first time.
3. A set of Fe/Si MLF exhibiting a strong AF coupling were pre-
pared and their measured MO and optical properties were compared
with the simulated ones based on different models of MLF.
4. It was shown that neither Si, amorphous FeSi2, ε-FeSi nor even
metallic α-FeSi2 could be considered as the interfacial spacers pro-
viding the strong AF coupling.
5. The optical properties of the spacer for the as-deposited Fe/Si
MLF were extracted that strongly supports its metallic nature. This
fact allows us to suggest that the AF coupling in the Fe/Si MLF is
provided by the metallic spacer.
6. The calculated optical properties for the B2-phase FeSi silicide
were compared with the experimentally extracted spectra of the sili-
cide spacer that mediates a strong AF coupling in the Fe/Si MLF
with relatively thick sublayers. The results also strongly suggest
that the spacer is a metallic FeSi silicide.
7. Unlike the traditional structural methods, an optical approach
166 Yu. V. Kudryavtsev, V. N. Uvarov, R. Gontarz, J. Dubowik, Y. P. Lee et al.
based on the comparison of the experimental and modelled as well as
theoretically calculated optical properties allowed us to identify the
structural transformations, induced in the investigated 3d-TM/Si
MLFs by IBM or thermal annealing, which were not detected by the
traditional XRD method. We think that the differences in sensitiv-
ities is connected not with the difference in the probing depth but
with basic conditions for the formation of x-ray diffracted beam and
main features of the energy band structures.
ACKNOWLEDGMENTS
This work was supported by the project 59/04-H of the N.A.S. of
Ukraine and by the KOSEF through Quantum Photonic Science
Research Center.
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| id | nasplib_isofts_kiev_ua-123456789-125813 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1608-1021 |
| language | English |
| last_indexed | 2025-12-07T18:17:01Z |
| publishDate | 2005 |
| publisher | Інститут металофізики ім. Г.В. Курдюмова НАН України |
| record_format | dspace |
| spelling | Kudryavtsev, Yu.V. Uvarov, V.M. Gontarz, R. Dubowik, J. Lee, Y.P. Rhee, J.Y. Makogon, Yu.N. Pavlova, E.P. 2017-11-04T17:59:15Z 2017-11-04T17:59:15Z 2005 Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications / Yu.V. Kudryavtsev, V.M. Uvarov, R. Gontarz, J. Dubowik, Y.P. Lee, J.Y. Rhee, Yu.N. Makogon, E.P. Pavlova // Успехи физики металлов. — 2005. — Т. 6, № 2. — С. 135-168. — Бібліогр.: 62 назв. — англ. 1608-1021 PACS: 75.70.-i, 78.20.Bh, 78.20.Ls, 78.66.-w, 78.67.-n, 79.20.Rf DOI: https://doi.org/10.15407/ufm.06.02.135 https://nasplib.isofts.kiev.ua/handle/123456789/125813 The aim of the paper is to show the potential of the spectroscopic ellipsometry and magnetooptical (MO) spectroscopy for probing of the multilayered films (MLF) with sublayer thickness of about a few nanometres. The main approach applied by us is based on the comparison of the experimental optical and MO properties with the simulated ones based on various models of the MLF. Specifically, as shown, such an approach can be useful for studying the nature of unusual MO properties and the interfaces in MLF comprising the noble and 3d-transition metals (3d-TM). The high sensitivity of the applied spectroscopic methods for the monitoring of the solid-state reactions in the 3d-TM/Si MLF induced by ion-beam treatment or by thermal annealing is also demonstrated. The optical properties of various silicides formed spontaneously or induced by various treatments at interfaces are evaluated experimentally and compared with the results of first-principle calculations. В данной работе показаны возможности спектральной эллипсометрии и магнитооптической (МО) спектроскопии для изучения структуры и особенностей физических свойств многослойных металлических пленок (МСП) с толщинами составляющих слоев порядка единиц нанометров. Основной подход исследования базируется на сравнении экспериментально измеренных оптических и МО свойств МСП с модельными, полученными для различных моделей структуры МСП. Было показано, что данный подход позволяет выяснить природу необычных МО свойств, а также структуру интерфейсной области в МСП, состоящих из слоев благородных и 3d-переходных металлов (ПМ). Также в работе продемонстрирована высокая чувствительность спектральной эллипсометрии для изучения твердотельных реакций в МСП 3d-ПМ/Si, вызванных ионной бомбардировкой или термическим отжигом. Оптические свойства различных силицидов 3d-ПМ, сформированных спонтанно либо в результате различных воздействий на МСП, были изучены экспериментально и сравнены с результатами теоретических первопринципных расчетов. В даній роботі показані можливості спектральної еліпсометрії та магнітооптичної (МО) спектроскопії для вивчення структури та особливостей фізичних властивостей багатошарових металевих плівок (БШП) з товщинами складаючих їх шарів порядку одиниць нанометрів. Основний підхід дослідження базується на порівнянні експериментально одержаних оптичних та МО властивостей БШП з модельними, що були одержані для різних моделей структури БШП. Було показано, що даний підхід дозволяє визначити природу незвичайних МО властивостей, а також природу інтерфейсної області БШП, що складаються з шарів благородних та 3d-перехідних металів (ПМ). В роботі також паказана висока чутливість спектральної еліпсометрії для вивчення твердотільних реакцій в БШП 3d-ПМ/Si, зумовлених іонним бомбардуванням або термічним відпалом. Оптичні властивості різних силіцидів 3d-ПМ, що було зформовані спонтанно або завдяки зовнішньому впливу, були вивчені експериментально та порівняні з результатами теоретичних першопринципних розрахунків. en Інститут металофізики ім. Г.В. Курдюмова НАН України Успехи физики металлов Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications Оптическая и магнитооптическая спектроскопия наноструктурных многослойных пленок: возможные приложения Оптична та магнетооптична спектроскопія наноструктурних багатошарових плівок: можливі застосування Article published earlier |
| spellingShingle | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications Kudryavtsev, Yu.V. Uvarov, V.M. Gontarz, R. Dubowik, J. Lee, Y.P. Rhee, J.Y. Makogon, Yu.N. Pavlova, E.P. |
| title | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications |
| title_alt | Оптическая и магнитооптическая спектроскопия наноструктурных многослойных пленок: возможные приложения Оптична та магнетооптична спектроскопія наноструктурних багатошарових плівок: можливі застосування |
| title_full | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications |
| title_fullStr | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications |
| title_full_unstemmed | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications |
| title_short | Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications |
| title_sort | optical and magnetooptical spectroscopy of the nanostructural multilayered films: possible applications |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/125813 |
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