Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation
The results of experimental researches dealing with formation of nanometricsize doped (Ag) layers on the surface (0001) between Te⁽¹⁾–Te⁽¹⁾ telluride quintet layers in Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) crystals under directed crystallization has been submitted. During the crystal growth as result of impur...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2009
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| Цитувати: | Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation / F.K. Aleskerov, S.K. Kahramanov, М.М. Asadov, K.S. Kahramanov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2009. — Т. 12, № 1. — С. 72-76. — Бібліогр.: 4 назв. — англ. |
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irk-123456789-1186052017-05-31T03:06:27Z Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation Aleskerov, F.K. Kahramanov, S.K. Asadov, М.М. Kahramanov, K.S. The results of experimental researches dealing with formation of nanometricsize doped (Ag) layers on the surface (0001) between Te⁽¹⁾–Te⁽¹⁾ telluride quintet layers in Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) crystals under directed crystallization has been submitted. During the crystal growth as result of impurity diffusion along a surface (0001), accumulation, redistribution and nanocrystal formation between Te⁽¹⁾–Te⁽¹⁾ layers occur. By the method of atomic-force microscopy, the Bi₂Te₃-хSex 〈Ag〉 crystal images with nanolayers were obtained. Being based on experimental data, the fractal dimension of nanocrystalline layers was estimated. 2009 Article Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation / F.K. Aleskerov, S.K. Kahramanov, М.М. Asadov, K.S. Kahramanov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2009. — Т. 12, № 1. — С. 72-76. — Бібліогр.: 4 назв. — англ. 1560-8034 PACS 81.05.Hd, 81.05.Ys, 81.10.Dn http://dspace.nbuv.gov.ua/handle/123456789/118605 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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The results of experimental researches dealing with formation of nanometricsize doped (Ag) layers on the surface (0001) between Te⁽¹⁾–Te⁽¹⁾ telluride quintet layers in Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) crystals under directed crystallization has been submitted. During the crystal growth as result of impurity diffusion along a surface (0001), accumulation, redistribution and nanocrystal formation between Te⁽¹⁾–Te⁽¹⁾ layers occur. By the method of atomic-force microscopy, the Bi₂Te₃-хSex 〈Ag〉 crystal images with nanolayers were obtained. Being based on experimental data, the fractal dimension of nanocrystalline layers was estimated. |
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| author |
Aleskerov, F.K. Kahramanov, S.K. Asadov, М.М. Kahramanov, K.S. |
| spellingShingle |
Aleskerov, F.K. Kahramanov, S.K. Asadov, М.М. Kahramanov, K.S. Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Aleskerov, F.K. Kahramanov, S.K. Asadov, М.М. Kahramanov, K.S. |
| author_sort |
Aleskerov, F.K. |
| title |
Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation |
| title_short |
Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation |
| title_full |
Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation |
| title_fullStr |
Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation |
| title_full_unstemmed |
Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation |
| title_sort |
bi₂te₃-хsex 〈ag〉 (х = 0.04) nanocrystal formation |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2009 |
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http://dspace.nbuv.gov.ua/handle/123456789/118605 |
| citation_txt |
Bi₂Te₃-хSex 〈Ag〉 (х = 0.04) nanocrystal formation / F.K. Aleskerov, S.K. Kahramanov, М.М. Asadov, K.S. Kahramanov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2009. — Т. 12, № 1. — С. 72-76. — Бібліогр.: 4 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
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AT aleskerovfk bi2te3hsexagh004nanocrystalformation AT kahramanovsk bi2te3hsexagh004nanocrystalformation AT asadovmm bi2te3hsexagh004nanocrystalformation AT kahramanovks bi2te3hsexagh004nanocrystalformation |
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2025-07-08T14:18:36Z |
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2025-07-08T14:18:36Z |
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1837088707717365760 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 1. P. 72-76.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
72
PACS 81.05.Hd, 81.05.Ys, 81.10.Dn
Bi2Te3-хSex 〈Ag〉 (х = 0.04) nanocrystal formation
F.K. Aleskerov1, S.K. Kahramanov1, М.М. Asadov2,*, K.S. Kahramanov1
1Production Association, Azerbaijan National Academy of Sciences
2Institute of Chemical Problems, Azerbaijan National Academy of Sciences
AZ 1143 Baku, G. Javid av., 29
*E-mail: mirasadov@yandex.ru; mirasadov@gmail.com
Abstract. The results of experimental researches dealing with formation of nanometric-
size doped (Ag) layers on the surface (0001) between Te(1)–Te(1) telluride quintet layers
in Bi2Te3-хSex〈Ag〉 (х = 0.04) crystals under directed crystallization has been submitted.
During the crystal growth as result of impurity diffusion along a surface (0001),
accumulation, redistribution and nanocrystal formation between Te(1)–Te(1) layers occur.
By the method of atomic-force microscopy, the Bi2Te3-хSex〈Ag〉 crystal images with
nanolayers were obtained. Being based on experimental data, the fractal dimension of
nanocrystalline layers was estimated.
Keywords: nanomaterial, low-dimensional structure, atomic-force microscopy.
Manuscript received 22.07.08; accepted for publication 18.12.08; published online 02.03.09.
1. Introduction
Fractal structures have a dimension incompatible with
dimensionality of space where they exist. By a fractal
cluster merging, the fractal surfaces can be formed.
Those can be doped by formations between layers in
layered crystals intercalated by the diffusion method.
Such nanoformations can have a fractal structure. To
explain the fractal structure, various models, subject to
fractal aggregate formation features and experimental
results, are used. The model of particle displacement
process under action of random forces, which is a type
of the Brownian movement, results in processes with
fractal time. The plots of particle displacement
dependence on time are fractal curves that can be used
for description of diffusive growth of possible fractal
formations. This situation occurs in real systems, for
example, in nanoparticle formation inside A2
VB3
VI-type
crystal layers [1].
The fractal time series of such quantities as layered
deposits in various media and interlaminar formations in
layered crystals can be estimated by the method of
normalized swing [2]. These measurement sequences are
characterized by the Hurst parameter Н. The
measurement record representing the fractal dimensional
curve is characterized by D = 2 – Н equality.
For many time series, the observable natural
normalized swing, i.e. dimensionless ratio R/S is well
described by the empirical relation R/S = (τ/2)H, S –
standard deviation, i.e., the square root of dispersion; R –
swing, i.e., the difference between maximal and minimal
accumulated natural observable inflow; τ – duration of
selected time interval. In this case, the parameter Н is
symmetrically distributed around the average value 0.73
with a standard deviation 0.09. The value Н for layered
deposits is 0.74 and H = 0.79 for fractal “tree” rings.
Apart from methods of normal fractal Brownian
function construction, there are also known ways of the
Brownian surface and volume construction. For
example, fractal Brownian curves obtained by the
algorithm of sequential random additions of Voss [3] at
different Hurst parameter Н (0.9; 0.5; 0.1) values.
The fractal aggregates can also be formed inside
interlaminar spaces of various layered crystals. Formed
inside interlaminar space of Te(1)–Te(1) telluride quintets
of Bi2Te3 and Sb2Te3 crystals, the nanoparticles,
according to [1], have fractality attributes. Results of
studying the process of nanofractal “assemblage”
formation in Bi2Te3-impurity system on Bi2Te3-хSex〈Ag〉
(х = 0.04) samples are submitted below.
2. Experimental techniques
The relief of assemblage surface of interlaminar
nanofractals has been investigated using the method of
atomic-force microscopy (AFM). To investigate spatial
distributions of fractal nanoclusters, the discrete Fourier
transform of cluster images was used.
The Bi2Te3-хSex〈Ag〉 (х = 0.04) system samples
with impurities were grown by the method of vertically
directed crystallization in graphitized quartz ampoules at
1000 К temperature with ~200 K/cm temperature
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 1. P. 72-76.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
73
gradient; the velocity of crystallization zone travel was
1.2 cm/h. Using a scanning atomic-force microscope
(mark NC-AFM), the relief of samples with nanofractal
formations was investigated.
Pure surface preparation was implemented by a
crystal cleavage of solid solutions of Bi2Te3 – Bi2Se3
system with impurities, along a plane (0001) on open-air
right before investigation. Investigation of their surfaces
was implemented by X-ray diffractometer and AFM
images. The analysis showed the absence of harmful
impurity content, in particular, oxygen in the obtained
crystals. Specifically, the X-ray images argue presence of
Ag, Ag2Te, Ag2Se, BiTe nanofragment traces on the
Bi2Te3-хSex〈Ag〉 (х = 0.04) crystal surface (0001) (Fig. 1).
After a special cutting, the samples have been
cleaved. For cleavage, the knife of hard metallic alloy
has been used.
3. Results and discussion
The experimental fact characterized by the perpendicular
nanoparticle growth on a Bi2Te3-хSex〈Ag〉 crystal plane
(0001) has been revealed. The implemented AFM
investigation of the Bi2Te3-хSex〈Ag〉 surface (0001) relief
in three-dimensional (3D) scale is represented in Fig. 2.
The Bi2Te3-хSex〈Ag〉 surface (0001) relief is given in
Fig. 3. The AFM-image in 2D scale is represented in
Fig. 4. On the right of the figure, the result of analysis of
surface properties is shown as a value histogram of the
same sample image elements.
As it follows from detail AFM-image analysis,
Bi2Te3-хSex〈Ag〉 surface (0001) consists of two sorts of
nanofractals. These nanofragments consist of silver
chalcogenides and silver particles. The nanofractal size
range is within 138 and 69 nm, accordingly, i.e. smaller
sizes (∼69 nm) belong to Ag. It follows from the
histogram (Fig. 4) that ledge size range is within 4-8 nm;
the maximal number of particles (N = 3800) has
h = 6 nm height. The distribution function of roughness
on a Bi2Te3-хSex〈Ag〉 surface along z axis of the sample
is more or less homogeneous.
Fig. 1. X-ray diffractometer record of Bi2Te3-хSex〈Ag〉
(x = 0.04) crystal surface (0001). 1 – Bi2Te3; 2 – Ag, Bi2Te3,
Ag2Te, BiTe; 3 – Bi2Te3, Ag2Te; 4 – Ag, Bi2Te3, Ag2Te, BiTe;
5 – Bi2Te3, Ag2Te; 6 – Ag2Te; 7 – Ag; 8 – Bi2Te3, BiTe; 9 –
Bi2Te3, Ag2Te; 10 – Ag2Te, BiTe; 11 – Ag2Te, BiTe.
Fig. 2. AFM-image of Bi2Te3-хSex〈Ag〉 (x = 0.04) crystal
surface (0001) in 3D scale.
The particle distribution function, i.e. its Fourier
transform, is shown in Fig. 5. This function shows the
distribution of particles with identical sizes. Presence of
distinguished wavevectors in the Fourier transform
argues the existence of the nanoparticles with typical
scale (distance between fractals) in initial image, where
this ordering appears.
The comparison of revealed interlaminar fractal
images with known structures [3, 4] showed their
significant similarity. The nanofractal interlaminar
doped surfaces between Te(1)–Te(1) in Bi2Te3-хSex〈Ag〉
(Fig. 5) are similar to landscapes, constructed by the
Voss algorithm [3]. If all the points are transformed by
the same way, then this procedure results in self-affine
surfaces. The images of surface horizontal sections,
obtained by us, are similar to known structures with the
fractal dimension D = 2 – Н. These sections are similar
to fractal Brownian lines with D = 1.5. These surfaces
consisting of infinite number of layers are usually called
as Brownian surfaces. This has to do with the fact that
any vertical section of this surface looks like a curve
typical for the Brownian movement. This surface on the
average satisfies the similarity relation and has
Н = 3 – D = 0.5.
Fig. 3. Relief of Bi2Te3-хSex〈Ag〉 (x = 0.04) crystal surface
(0001) (along х axis the scanning area is represented by
dx ≈ 100 nm).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 1. P. 72-76.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
74
For fractal surfaces represented by us in Fig. 2, as
well as for all known similar self-affine fractals, the
local and global fractal dimensions should be
distinguished. In the case D > 2 (in this example
Dsurf = 2.5), we have a local surface dimension (Dsurf).
Let us consider the surfaces inside interlaminar
spaces where doped fractal structures are formed
(Fig. 2). If on one of the obtained landscapes we cut
horizontal section off, then we shall have images as
“island” and “coastlines”. The fractal dimension of these
lines obtained by surface section with a plane makes D =
2 – Н = 1.5. The nonintegral value (1 < D < 2) argues
the flat fractal structure.
In the theory of fractals, there are three types of
dimension connected with a self-affine surface: surface
dimension Dsurf, which is local self-affine surface, profile
dimension Dpr, which is also local and self-affine,
contour dimension Dc, which is a self-similar dimension.
These fractal dimensions are related to each other by the
ratio: Dpr = Dc = Dsurf – 1. For Dc = Dsurf – 1 = 2.5 – 1
= 1.5. The obtained experimental data (Figs. 2-5) argue
that Bi2Te3-хSex〈Ag〉 single crystals are characterized by
fractal structures. These fractal structures can be
considered as objects with disordered structure
“immersed” into Euclidean space of Te(1)–Te(1) layers of
Te3-хSex〈Ag〉, and structure objects are perpendicularly
directed to a basic plane (0001).
The nature of fractal structure formation on a free
surface and inside interlaminar space of Bi2Te3-хSex〈Ag〉,
Bi2Te3〈Cu〉, Bi2Te3〈Ni〉, Bi2Te3〈B〉, Bi2Te3〈Sn〉,
Bi2Te3〈Сd〉, Bi2Te3〈In〉, Sb2Te3〈Se〉, Sb2Te3〈Cd〉 layered
crystals is similar. The fractal structure of these crystals
appears in distribution properties of doped layers between
Te(1)–Te(1) telluride quintets. For these layers, the
following situation is realized: fractal structure properties
appear within the scale range bounded below by ~ (5-
10) nm size, forming a fractal aggregate, and bounded
above by the initial fractal cluster size (1000 nm).
The data for D = 2.5 structures are comparable with
results [2] by the fractal dimension of (particles) clusters
formed in a solid particle association.
In the aggregation model [2-4] characterizing the
Brownian movement subject to particle cluster, it is
accepted that the associating particles are in diffusion
spatial motion. I.e., the particle free path in this case is
small in comparison with characteristic dimensions of
area responsible for fractal growth. The experimental
data for mean values of fractal dimensions in a particle
association in three-dimensional space (in the model of
Brownian movement aggregation) gave the value
D = 2.46± 0.05 and D = 1.68± 0.02 for two-
dimensional space.
In the model of fractal cluster growth on a
substrate, when cluster sprouts under solid particle
Fig. 4. AFM-image of Bi2Te3-хSex〈Ag〉 (x = 0.04) crystal surface (0001) in 2D scale (histogram is in the right corner).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 1. P. 72-76.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
75
adhesion to a substrate [3], it is accepted that, growing
three-dimensional cluster is formed on a flat substrate. In
this case, the crosscut cluster size is significantly less
than substrate sizes, and attached particles execute a
spatial motion, i.e., clusters sprout from a plane.
According to another model [4], the formed cluster
is similar to “wood” of separate “whiskers”, sprouting
from a plane. In this case, the growth mode is
considered, when cluster growth from a plane is possible
only in perpendicular direction to a plane, and clusters
look like a “sticks”. These structures are considered for
fractal landscapes obtained by the Voss algorithm.
In crystals based on Bi2Te3, the characters of bond
between atoms in one layer and between layers are
various. The bonds between Te(1)–Te(1) telluride quintets
are realized by van der Waals type forces, while inside
Te(1)–Te(1) quintets the ion-covalent forces are prevailing.
The principal cause, resulting in cleavage of layered
crystals based on Bi2Te3 under mechanical loads, is
weakness of interlaminar bonds.
On plane surfaces (0001) of crystals based on
Bi2Te3 (Fig. 2) under investigation, it is possible to
notice the presence of forming nanolayers and different
size islet traces on them. The nanolayer formation in
crystals based on Bi2Te3 can be related with draining of
diffusing doped atoms (silver, copper and small amounts
of nickel) from Te(1)–Te(1) telluride quintets and other
defects inside interlayers.
The draining periods of doped atoms occur stage by
stage: at the first stage the number of passed atoms is not
enough and they occupy a small part of interlayer
surface. I.e., the doped atoms concentrate in a small
amount. With the lapse of time, their concentration
reaches the saturation; being merged into nanoparticles
they form nanoislets. The process consists of continuous
layer formation, on which the finite-size islets
concentrate. The total islet amount significantly
decreases as a consequence of discrete diffusion particle
displacement on short distances, which results in islet
merging into one large islet. At the next stage of
layer growth, the interlaminar space, in particular
Bi2Te3-хSex〈Ag〉, gets the greater part of Ag atoms from
telluride quintets. The process reaches its peak when
islets contact with each other with narrowed tips and
merge into conglomerates without total merging. As a
result, the fractal cluster formation should occur,
forming as a result of particle association subject to the
diffusion character of their movement.
4. Conclusions
It follows from experimental data that the obtained
fractal structures of Bi2Te3-хSex〈Ag〉 crystals have
various sizes at the expense of initiation time
fluctuation. The beginning of peak formation occurs
Fig. 5. Distribution function of particles with identical sizes (Fourier transforms).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2009. V. 12, N 1. P. 72-76.
© 2009, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
76
after their basis formation mainly on telluride quintets.
At the output of vacancy islet surface, diffusion with
Ag atom output on a plane (0001) occurs, too, which
enlarges and raises the heights of forming fractals. The
similar situation can be reflected on AFM 3D images in
fractal structure formation depending on atomic radii of
dopants (for example, Cu and Ni). Thus, as a result of
growth of particle sizes between Te(1)–Te(1) layers in
Bi2Te3-хSex〈Ag〉 the gradual growing fractal structures
are formed, filling of which results in fractal surface
formation on a basic plane (0001). On a crystal surface
(0001), the nanocrystals are formed sooner by self-
organization and create visual nanofractal assemblages
covering all the Bi2Te3-хSex〈Ag〉 basic surface (0001). In
connection with nanostructure formation in semi-
conductors, the fractal nanostructures with large sizes
(> 20–25 nm) obtained by us can cause a practical
interest due to the influence on properties of
semiconductor crystals.
References
1. F.K. Aleskerov, S.K. Kahramanov, E.M. Derun,
Some features of formation of nanoobjects in
interlayer space of crystals such as Bi2Te3 // Fizika.
J. National Acad. Sci. Azerbaijan, Baku, p. 41-47
(2007).
2. H.E. Hurst, R.P. Black, V.M. Simaika, Long-Term
Storage: An Experimental Study. Pergamon,
London, 1965, p. 230.
3. B.M. Smirnov, Physics of Fractal Clusters. Nauka,
Moscow, 1991, p. 192 (in Russian).
4. P. Meakin, Fractal structures // Progress in Solid
State Chemistry 20 (3), p. 135-233 (1990).
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