Microplasticity of subsurface layers of diamond-like semiconductors under microindentation
Experimental confirmations of the influence of the free surface of a chip on processes of plastic deforming under indentation such as a decrease of the effective activation energy of dislocations with reduction of load on the indenter and a considerable decrease of temperature of the beginning of po...
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Донецький фізико-технічний інститут ім. О.О. Галкіна НАН України
2005
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| Цитувати: | Microplasticity of subsurface layers of diamond-like semiconductors under microindentation / V.A. Nadtochiy, V.P. Alyokhin, M.M. Golodenko // Физика и техника высоких давлений. — 2005. — Т. 15, № 1. — С. 44-49. — Бібліогр.: 20 назв. — англ. |
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irk-123456789-701082014-10-29T03:01:39Z Microplasticity of subsurface layers of diamond-like semiconductors under microindentation Nadtochiy, V.A. Alyokhin, V.P. Golodenko, M.M. Experimental confirmations of the influence of the free surface of a chip on processes of plastic deforming under indentation such as a decrease of the effective activation energy of dislocations with reduction of load on the indenter and a considerable decrease of temperature of the beginning of polygonization processes, when annealing microhardness rosettes in the field of small impresses, are obtained. A possibility of dislocation motion by means of creeping at temperatures lower than brittleness threshold temperature was shown on the example of GaAs. 2005 Article Microplasticity of subsurface layers of diamond-like semiconductors under microindentation / V.A. Nadtochiy, V.P. Alyokhin, M.M. Golodenko // Физика и техника высоких давлений. — 2005. — Т. 15, № 1. — С. 44-49. — Бібліогр.: 20 назв. — англ. 0868-5924 PACS: 61.72.Ff http://dspace.nbuv.gov.ua/handle/123456789/70108 en Физика и техника высоких давлений Донецький фізико-технічний інститут ім. О.О. Галкіна НАН України |
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Experimental confirmations of the influence of the free surface of a chip on processes of plastic deforming under indentation such as a decrease of the effective activation energy of dislocations with reduction of load on the indenter and a considerable decrease of temperature of the beginning of polygonization processes, when annealing microhardness rosettes in the field of small impresses, are obtained. A possibility of dislocation motion by means of creeping at temperatures lower than brittleness threshold temperature was shown on the example of GaAs. |
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Article |
| author |
Nadtochiy, V.A. Alyokhin, V.P. Golodenko, M.M. |
| spellingShingle |
Nadtochiy, V.A. Alyokhin, V.P. Golodenko, M.M. Microplasticity of subsurface layers of diamond-like semiconductors under microindentation Физика и техника высоких давлений |
| author_facet |
Nadtochiy, V.A. Alyokhin, V.P. Golodenko, M.M. |
| author_sort |
Nadtochiy, V.A. |
| title |
Microplasticity of subsurface layers of diamond-like semiconductors under microindentation |
| title_short |
Microplasticity of subsurface layers of diamond-like semiconductors under microindentation |
| title_full |
Microplasticity of subsurface layers of diamond-like semiconductors under microindentation |
| title_fullStr |
Microplasticity of subsurface layers of diamond-like semiconductors under microindentation |
| title_full_unstemmed |
Microplasticity of subsurface layers of diamond-like semiconductors under microindentation |
| title_sort |
microplasticity of subsurface layers of diamond-like semiconductors under microindentation |
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Донецький фізико-технічний інститут ім. О.О. Галкіна НАН України |
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2005 |
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http://dspace.nbuv.gov.ua/handle/123456789/70108 |
| citation_txt |
Microplasticity of subsurface layers of diamond-like semiconductors under microindentation / V.A. Nadtochiy, V.P. Alyokhin, M.M. Golodenko // Физика и техника высоких давлений. — 2005. — Т. 15, № 1. — С. 44-49. — Бібліогр.: 20 назв. — англ. |
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Физика и техника высоких давлений |
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2025-07-05T19:24:58Z |
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| fulltext |
Физика и техника высоких давлений 2005, том 15, № 1
44
PACS: 61.72.Ff
V.A. Nadtochiy1, V.P. Alyokhin2, M.M. Golodenko1
MICROPLASTICITY OF SUBSURFACE LAYERS OF DIAMOND-LIKE
SEMICONDUCTORS UNDER MICROINDENTATION
1Slovyansk State Pedagogical University
19 Gen. Batyuk St, Slovyansk, 84116, Donetsk Reg., Ukraine
Е-mail: slavgpi@slav.dn.ua
2Moscow State Industrial University
16 Avtozavodskaya St, Moscow, 109280, Russia
Е-mail: topstaff@msiu.ru
Experimental confirmations of the influence of the free surface of a chip on processes of
plastic deforming under indentation such as a decrease of the effective activation energy
of dislocations with reduction of load on the indenter and a considerable decrease of
temperature of the beginning of polygonization processes, when annealing microhardness
rosettes in the field of small impresses, are obtained. A possibility of dislocation motion
by means of creeping at temperatures lower than brittleness threshold temperature was
shown on the example of GaAs.
The researches of last years have shown a possibility of plastic deformation in
diamond-like chips below plasticity threshold temperature down to temperature of
liquid nitrogen. However the mechanism by which the crystal form is changed is
not completely clarified with reference to conditions of microindentation (the
main technique of microplasticity detection in conditions of high brittleness of
objects). A number of experimental data testifies to an essential influence of ab-
normal features of the facilitated origination and motion of dislocations in near-
surface area of a chip on the general kinetics of the deforming of stuff, including the
area below the brittleness threshold temperature. Considerations about possibility of
non-dislocation mass transfer mechanism and about essential part of point defects
in dislocation motion in covalent crystals under indentation have been suggested,
though in the structural plan these problems have not been treated yet.
In this work a special role of the surface in dislocation motion facilitated, as
contrasted to the motion in the volume, was investigated. By the straight structural
methods on the example of GaAs the change of dislocation motion mechanism
from slip to creeping at the transition into the temperature range of brittle failure
has been shown. The point defects are playing the determining role in this process.
Физика и техника высоких давлений 2005, том 15, № 1
45
a b
Fig. 1. A dislocation rosette near to the indenter impress on the plane (111) of Si single
crystal (test temperature 1000 K) (a) and the deformed area detected by the level-by-level
etching (b)
The tests were conducted on Si single crystals. The sample was deformed with
indenter on plane (111) at 1000 K by means of the device PMT-3 equipped with a
heater. After processing with the selective Sirtl etchant a characteristic rosette
(Fig. 1,a) from dislocations moving in slip planes {111} inclined to the chip sur-
face and intersecting it along directions 〈110〉 was revealed near to the impress.
In Fig. 1,b the configuration of plastically deformed area obtained during the
level-by-level analysis of dislocation structure is shown. The deformed area is
shown in section along a ray of the rosette. It was important to find out how the
deformed area changes at reduction of the penetration depth of the indenter into
semiconductor. The ratios of the characteristic dimensions l/he and l/hf were taken
as criteria for estimation. Here l – the maximum ray length, he – bedding depth of
rays, hf – full bedding depth of dislocations.
The results of researches in coordi-
nates l/h = f(h) are represented in Fig. 2.
The obtained data demonstrate evident
tendency to primary propagation of
dislocation half-loops of the rays in a
thin near-surface layer i.e. to some
stretching of the deformed area along
the surface, while the size of the im-
press decreases. The observed regu-
larities can be explained from a posi-
tion that motility of dislocations in-
creases when deformations are local-
ized in a thin near-surface layer [1].
It was of interest to find out, how
the energy parameters of plastic flow-
ing under indenter change when de-
formation is localized in a thin near-
Fig. 2. The change of the geometrical para-
meters l/he (curve 1) and l/hf (curve 2) of the
deformed area depending on the penetration
depth of the indenter. For curve 1 h = he,
for curve 2 h = hf
Физика и техника высоких давлений 2005, том 15, № 1
46
surface layer. With this purpose impresses of a standard Vickers indenter were
made at temperature 300 K under loads from 25 up to 200 mN on a chemically
polished surface of dislocationless mark GDG-10 Ge. Then indenter was removed
and the chips were annealed in inert medium at different temperatures in the interval
700−800 K during 45 min. After detecting the dislocation structure in selective
etchant the measurement of rays of maximum length were carried out (1-2 rays in
each rosette). For each load the measurements were carried out on 25-30 rosettes.
A simple method of estimating the running velocity of single dislocations in
chips with diamond grating from the analysis of dislocation rosettes detected near
impresses and obtained at temperatures higher than the brittleness threshold or
after the annealing of impresses made at room temperature was offered in [2]. The
method is based on usage of an empirical equation for velocity of dislocations
)/exp( kTUB m −τ=ν , (1)
where U – activation energy of motion of dislocations; B, m – constants; τ – act-
ing stresses, k – Boltzmann constant; T – absolute temperature. Having accepted
stress acting on dislocation, which moves in the force field under indenter, ac-
cording to [3]:
)(6
)21(
22
22
xy
xyP
+π
−ν−
=τ , (2)
where ν – Poisson’s ratio; P – load on indenter; x, y – coordinates of an analyzed
point, Kabler et al. [4] have derived the final relation for the maximum length of a
rosette ray in the form
+
−+++
kTm
UtPBl mm
m
m
)12(
exp~ 12
1
1212
1
, (3)
where t – time of exposure under loading, constant m ≈ 1.
This method allows to determine the value of activation energy of dislocation
motion from the temperature relation ( )1lg −= Tfl . The values of effective acti-
vation energy of growth of dislocation rays in a rosette with temperature depend-
ing on load on the indenter are adduced in Table.
Table
Load on indenter P, mN Activation energy Ue, eV
200
100
50
25
0.59 ± 0.09
0.51 ± 0.23
0.3 ± 0.2
0.26 ± 0.08
Adduced in Table values of Ue are much lower than that known from literature
for Ge and obtained by direct measurement of the velocity of single dislocations
and dislocations moving at the head of a line. Chaudhuri et al. [4] for dislocations
Физика и техника высоких давлений 2005, том 15, № 1
47
moving at the head of a line have received U = 1.6 ± 0.05 eV. The low limit of the
spread corresponded to the highest tensions and upper one to the lowest. Kabler
[5] has established that for single screw dislocations the activation energy U =
1.47 eV at all stresses and for 60° it changes from 1.49 eV at τ = 80 MPa up to
2.25 eV at τ = 8 MPa. According to Schäfer [6], who investigated mobility of sta-
bilized single dislocations in the stress range 1−150 MPa, the activation energy is
1.62 ± 0.1 eV. Johnson [7] for high levels of stresses (up to 600 MPa) adduces
U = 1.4−2.2 eV.
Our data in coordinates l = f(T) are adduced in Fig. 3. The curves 5 and 6 are taken
from [8]. They also are obtained while testing Ge single crystals on a plane (111), but
at loads on indenter of 1 kN and 2 kN. It is known [8] that the maxima on curve l =
f(T) correspond to homologous temperature t* = T/Tm ≈ 0.85 (Tm = 1209 K – Ge
melting temperature) at which a sharp temperature dependence of critical shearing
stress begins. At the annealing temperature t > t* the process of formation of a
dislocation rosette is more and more determined by the development of polygoni-
zation processes which hamper the scattering of dislocations in their slip planes.
In the mentioned temperature range the rapid deceleration of growth of dislocation
rays is observed. The value t* characterizes a changing of the plastic deformation
mechanism. It is intimately connected to rigidity of the crystal lattice relatively to
motion of dislocations [8]. The results in Fig. 3 demonstrate that while load on the
indenter is decreasing the maximum on the curves l = f(T) is essentially moving
into the area of lower temperatures down to t ≈ 0.55.
The results of the first and second
series of experiments testify to chan-
ges of plastic deformation conditions
at indenting thin near-surface layers of
diamond-like semiconductors.
It was shown [9,10] that conditions
of slip of dislocation loops resting on
the surface of the chip do not corre-
spond directly to any model [10−12]
owing to essential influencing of the
surface on motion of dislocations.
Shown on the example of Ge and Si
[1] the capability of the surface to act
as a source and sink for vacancies
comes to the accelerated movement of
steps as a result of channel diffusion
of point defects that eases the motion
of bends. It is marked [13] that shape
and size of dislocation loops at their
thermally actuated slip in Ge and Si
are largely determined by vacancy
Fig. 3. Dependence of ray length of a dislo-
cation rosette on the annealing temperature
for the samples tested at room temperature
by microindenting with different loads on
the indenter P, 10−3 N: 1 − 25, 2 − 50, 3 −
100, 4 − 200, 5 − 1000, 6 − 2000
Физика и техника высоких давлений 2005, том 15, № 1
48
equilibrium concentration and rate of their diffusion, while in combinations A3B5,
where differences in motility of adjacent 60°, α and β dislocations are very great,
these parameters are determined mainly by concentration and rate of diffusion of
vacancies of a definite type.
The determining role of point defects in the facilitated motion of dislocation loops
near to the chip surface is demonstrated in our experiments on microindentation. The
experiments were conducted in the temperature range of brittle failure of diamond-like
semiconductors. The scattering of dislocations near to an indenter impress in the men-
tioned semiconductors at T ≈ 300 K is not detected by optical methods [14] because of
availability and stringent directivity of covalent bonds. At the same time experiments
on the uniaxial pressing of Ge [15−18] as well as our experiments on microindentation
of GaAs demonstrate a capability of scattering of dislocations if a chip with the marked
impresses is subjected to a long-term deformation by uniaxial pressing.
GaAs (AGChT-1-25а-1) single crystals in the shape of rectangular parallelepi-
peds with dimensions of ribs 2.4 × 3.1 × 3.2 mm oriented in the stated succession
accordingly to crystallographic directions [01 1 ], [011] and [100] (Fig. 4,a) were
used. The impresses were put on the lateral surfaces (011–) and (01–1) at loads on
the indenter of 200 mN. Then the sample was pressed along the direction [100] up
to the stress σ = 83 MPa and was maintained under loading during 120 h at 300 K.
After the removing of loading the dislocation structure shown in Fig. 4,b was de-
tected near to the impress by means of selective chemical etching. Each couple of
pits introduces apparently outlets of prismatic half-loop having stepped aside from
the area of stress concentration by creeping. In Fig. 4,a the flow of vacancies from
the right-hand side to the indenter impress is represented with the broken lines.
Under the uniaxial loading by pressure p = σxx the equilibrium vacancy con-
centration on end faces reduces to [10,19]:
)/exp(0 kTVCC axxσ−= , (4)
a b
Fig. 4. The deformed sample of GaAs with the marked indenter impress (labeled with a
dagger). The arrows indicate flows of vacancies (a). The dislocation structure near to the
indenter impress (b)
Физика и техника высоких давлений 2005, том 15, № 1
49
where C0 –equilibrium vacancy concentration in the unloaded chip, Va – atomic
volume. For lateral surfaces p = 1/3σxx and )3/exp(0 kTVCC axxσ−= . The flow
of vacancies from the lateral surfaces to the end faces (and to the indenter im-
press) appears owing to the arising difference of concentrations. Simultaneously
the flow of atoms in opposite direction appears. Near to an impress there is a su-
persaturation on interstitial sites [20]. Prismatic interstitial dislocation loops can
arise under the action of stresses and mentioned supersaturation. The flow of va-
cancies will promote their movement and partial stress relief near to the impress.
Thus in near-surface layers of diamond-like semiconductors the process alter-
nate to the thermally actuated mechanism of overcoming high Peierls barriers by
the slip of dislocations is realized. The thermally actuated mechanism requires, in
the brittle failure field, stresses of the order of idealized shear strength of chips. It
was shown that at high temperatures the motion of dislocations near to the surface
can occur owing to simultaneous slipping and creeping [1]. That conditions high
mobility of dislocations.
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