Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts
Results of Auger electron spectroscopy (AES) investigations of boron nitride whiskers produced in optical furnace without catalysts as well boron and initial h-BN for comparison are presented. The Auger process was initiated by exposing the sample to a beam of high energy electrons 3 keV.
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Sartinska, L.L. Stonis, V.V. Frolov, A.A. 2011-11-15T18:26:31Z 2011-11-15T18:26:31Z 2009 Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts / L.L. Sartinska, V.V. Stonis, A.A. Frolov // Современные проблемы физического материаловедения: Сб. научн . тр. — К.: ІПМ НАН України, 2009. — Вип. 18. — С. 49-53. — Бібліогр.: 7 назв. — англ. XXXX-0073 https://nasplib.isofts.kiev.ua/handle/123456789/28654 539.184.56:546.271: 543.422.8 Results of Auger electron spectroscopy (AES) investigations of boron nitride whiskers produced in optical furnace without catalysts as well boron and initial h-BN for comparison are presented. The Auger process was initiated by exposing the sample to a beam of high energy electrons 3 keV. We acknowledge support of STCU project No. 4133. en Інститут проблем матеріалознавства імені І.М. Францевича НАН України Современные проблемы физического материаловедения Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts Article published earlier |
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Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts |
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Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts Sartinska, L.L. Stonis, V.V. Frolov, A.A. |
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Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts |
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Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts |
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Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts |
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Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts |
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auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts |
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Sartinska, L.L. Stonis, V.V. Frolov, A.A. |
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Sartinska, L.L. Stonis, V.V. Frolov, A.A. |
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2009 |
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English |
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Современные проблемы физического материаловедения |
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Інститут проблем матеріалознавства імені І.М. Францевича НАН України |
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Results of Auger electron spectroscopy (AES) investigations of boron nitride whiskers produced in optical furnace without catalysts as well boron and initial h-BN for comparison are presented. The Auger process was initiated by exposing the sample to a beam of high energy electrons 3 keV.
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Auger electron spectroscopy of boron nitride whiskers produced in optical furnace without catalysts / L.L. Sartinska, V.V. Stonis, A.A. Frolov // Современные проблемы физического материаловедения: Сб. научн . тр. — К.: ІПМ НАН України, 2009. — Вип. 18. — С. 49-53. — Бібліогр.: 7 назв. — англ. |
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УДК 539.184.56:546.271: 543.422.8.
Auger electron spectroscopy of boron nitride whiskers
produced in optical furnace without catalysts
L. L. Sartinska, V. V. Stonis*, A. A. Frolov
*Kurdyumov Institute for Metal Physics of NASU, Kiev, Ukraine
Results of Auger electron spectroscopy (AES) investigations of boron nitride whiskers
produced in optical furnace without catalysts as well boron and initial h-BN for
comparison are presented. The Auger process was initiated by exposing the sample to a
beam of high energy electrons 3 keV.
Research of surface of solids is important for many fields in electronics, at
direct transformation of thermal, solar and chemical energy to electric, in
catalysis and other, where the purity of the produced materials and chemical
state of atoms has the special value in a near-surface layer.
Auger electron spectroscopy is a very powerful surface analytical technique
that has found applications in many fields of solid-state physics and chemistry.
Several phenomena such as adsorption, desorption, surface segregation from the
bulk, measurement of diffusion coefficients, and catalytic activity of surfaces
have been investigated using AES [1, 2]. The basic advantages of this technique
are its high sensitivity for chemical analysis in the 0,55- to 2 Å region near the
surface, a rapid data acquisition speed, its ability to detect all elements above
helium, and its capability of high-spatial resolution. The high-spatial resolution
is achieved because the specimen is excited by an electron beam that can be
focused into a fine probe. It was developed in the 1960s, when ultra-high
vacuum technology became commercially available [3].
Filamentary structures of BN, produced in an optical furnace in the
atmosphere of nitrogen [4—6] due to it structural peculiarities can differ by the
chemical state not only surface layer of atoms in a homogeneous and perfect
enough area of the surface from the chemical state of the second and subsequent
near-surface layers but also by the chemical state of imperfect inhomogeneous
area of polycrystalline surface of whiskers. Thus, study of power spectrums of
Auger-electrons for definition of element composition of solids and chemical
state of atoms of surface of BN whiskers can considerably extend the notion
about our produced structures.
It is known that almost any solid can be analyzed by AES. Our powder
samples were analyzed as there were and the analysis was done in high vacuum.
A pure aluminum (SIGMA-ALDRICH, 99%, particle size <75 μm) was added
to every sample for better estimation and for the removal of superficial charge
of the probed dielectric objects.
Boron nitride whiskers were selected for investigations. They were
produced in optical furnace without catalysts on the surface of compacted
samples of the initial powders. A quartz chamber was used for the process.
Heating of the surface of initial powders was done in a furnace of high intensity
optical energy in the flow of dryed and purified nitrogen. The optical furnace
involves three xenon tubes centered in the focus of three ellipsoidal reflectors.
© L. L. Sartinska, V. V. Stonis*, A. A. Frolov, 2009
49
A diameter of the light spot is 10 mm. The calculated value of the density of
the light flux energy in the focal zone is about E = 0,7·104 kW/m2 that
corresponds ~2000 K [3—5].
For comparison the initial powders of platelet-like fine-grained boron
nitride (Chempur, CH070802) have been used. These powders are h-BN
textured on 002 with impurity of B2O3. A diameter of platelets of boron nitride
is ~0, 6—1,0 μm and thickness — ~0,1 μm. Detail description of origin
powders and experimental presented in [4].
The Auger process was initiated by creation of a core hole carried out by
exposing the sample to a beam of high energy electrons 3 keV (beam current —
120, 180, 200 μmA; modulation — 1—2 eV; time constant — 3 sec; sensitivity —
50—100 μmV; scanning time — 1000 sec; energy rate — 500 eV). The high
energy electrons had sufficient energy to ionize proper levels of the lighter
elements, and higher core levels of the heavier elements. In general, since the initial
ionisation is non-selective and the initial hole may therefore be in various shells,
there will be many possible Auger transitions for a given element — some weak,
some strong in intensity. AES is based upon the measurement of the kinetic
energies of the emitted electrons. Each element in a sample being studied will give
rise to a characteristic spectrum of peaks at various kinetic energies.
It is known that the number of detected Auger electrons varies with
topography. Topographical corrections can be made only by comparing the
intensities of different elements in the same spectrum, because the effect of
topography is the same for all elements. So, intensities of our investigated
elements which enter into the composition of powders can vary from table data
(table) of the flat surfaces of materials in solid state.
Semiqauntitive calculations from differential Auger spectrum of the surface
of boron powders (fig. 1) demonstrated that boron powders have ~58% boron,
22% carbon and 20% oxygen. The AES peaks involving valence electrons
carry significant information about the chemical state of the surface. The
chemical effect may appear as a simple peak shift, a change in peak shape, or
both. The peak of carbon is shifted. It’s mean the presence BC or Al4C3 on the
surface. Oxygen is in adsorbed layer. Differential Auger spectrums (fig. 2)
from different parts of the upper layer of the surface of boron powders have
noise-like signals. However these spectrums also have shown the clear carbon
and oxygen peaks. These peaks are shifted, there are changes in their shapes and
their intensities. So, powders of boron and alumina have a lot of oxygen and
carbon on their surfaces, which can be components of different compounds such
as BC or Al4C3 , CO, CO2 and so on.
Kinetic energy and AES transition of B, C, N, O, Al
N Elements AES transition Kinetic energy of AES
transition, eV
1 Boron KLL 179
2 Carbon KLL 272
3 Nitrogen KLL 379
4 Oxygen KLL 508
5 Aluminum LMM 68
50
Fig. 1. Differential Auger spectrum of the upper layer of the surface of
boron powders.
Fig. 2. Differential Auger spectrums of the upper layer of the surface of
boron powders in different points.
Auger-spectroscopy of the initial plate-like fine-grained powders of h-BN
with the impurities of B2O3 has confirmed the results of X-ray diffraction analysis
[1—3] about the presence of enough large amount of oxygen in initial powder of
BN (fig. 3). Semiquatitive calculations from differential Auger spectrum of the
surface of boron nitride powders have demonstrate that upper layer of h-BN
have ~15% carbon, 20% oxygen, 31% boron, 34% nitrogen. Oxygen content is
the same like in boron, but it’s mean that its content is increased, because there
is nitrogen in composition. Carbon content decreased. It is, perhaps, because of
the method of h-BN powders production that effect also on a lack of nitrogen in
their stoichiometric composition in the surface layer.
There are far less oxygen in whiskers from BN and in the pure boron.
Presence of plenty amount of carbon on the surface of whiskers in comparison
to initial boron nitride it is possible to explain by over activity to adsorption of
hydrocarbons and CO from an atmosphere. Appearance of the divided peak of
the boron in initial h-BN and in whiskers from BN in comparison to the pure
boron nitride indicates the effect of nitrogen on the change of electronic boron
structure.
51
Fig. 3. Differential Auger spectrum of the upper layer of the
surface of boron nitride powders (a) and nitride whiskers (b).
Fig. 4. Auger electron spectra: a — boron; b — whiskers from
boron nitride; c — initial powder of h-BN.
52
Fig. 5. Auger electron spectra of carbon from CO
on W, W2C, graphite and diamond [7].
Comparing obtained differential Auger spectrums (fig. 4) with Auger
electron spectra of carbon from CO on W, W2C, graphite and diamond [6] (fig. 5)
it’s possible to make some explanations of shifting, shapes changes and change
of intensities of main peaks in boron and BN powders and also BN whiskers.
Shifting of boron peaks in BN powders and whiskers demonstrates close-
packed arrangement of these structures, which results in lowering of electronic
levels like in diamond (fig. 5). Moreover, close-packed arrangement of BN
whiskers structure gives rise to appearance additive peak in boron due to deeper
electronic levels splitting (fig. 4, b). Smooth peaks of oxygen in BN whiskers
like from CO on W (fig. 5) can give evidence of its adsorption state.
So, the Auger Electron Spectroscopy research indicates difference in
electronic structures of pure boron and boron in h-BN and in BN whiskers.
Presence of nitrogen results in lowering of electronic levels and appearance
additive peak in boron due to deeper electronic levels splitting. Catalyst-free
transformation of h-BN in optical furnace reduces oxygen content in material.
We acknowledge support of STCU project No. 4133.
1. Lander J. Auger peaks in the energy spectra of secondary electrons from various
materials // Phys. Rev. — 1953. — 91, 1382.
2. Kai Siegbahn. Electron spectroscopy for Atoms, Molecules fnd Condensed Matter.
Nobel lecture, 8 December, 1981. Nobel lectures. World Scientific. — 1995. — 1,
No. 2б. — P. 63.
3. Harris L. A. Analysis of materials by electron-excited. Auger electrons // J. Appl.
Phys. — 1968. — 39. — P. 1428.
4. Frolov A. A., Sartinska L. L., Koval’ A. Yu, Danilenko N. A. Using of optical
furnace for producing of nanostructure boron nitride. Nanostructure materials
science. — 2008. — No. 2—4. — С. 115—120 (in Russian).
5. Sartinska L. L., Frolov A. A., Koval’ A. Yu. et al. Transformation of Fine-grained
Graphite Boron Nitride Induced by Concentrated Light Energy. Materials
Chemistry and Physics. — 2008. — 109. — P. 20—25.
6. Frolov A. A., Andrievskaya E. P., Sartinska L. L. // Internat. conf. “Modern
Materials Science: Achievements & Problems", Proceedings, 26—30 Sept. 2005.
Kyiv, Ukraine, 174—175pp. (in Russian).
7. Czanderna A. W. “Methods of Surface Analysis”, Elsevier Scientific Publishing
Company, Amsterdam. — 1975. — 19.
53
L. L. Sartinska, V. V. Stonis*, A. A. Frolov
*Kurdyumov Institute for Metal Physics of NASU, Kiev, Ukraine
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