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5.Volkov A.A., Artemov V.G., Pronin A.V. A radically new suggestion about the electrodynamics of water: Can the pH index and the Debye relaxation be of a common origin? // EPL. – 2014. - V. 106. - P. 46004-1-6.

4.Volkov A.A., Artemov V.G., Volkov A.A. jn ., Sysoev N.N. Possible mechanism of molec-

ular motion in liquid water from dielectric spectroscopy data // J. Mol. Liq. – 2017. - V. 248. - . 564– 568.

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UDC 621.383.415

OPTICAL AND ELECTRIC PHENOMENA IN AMORPHIC FILMS OF GeS

DOPED REE

A.S. Alekperov1, O.M.Gasanov2, Kh.A. Adgezalova3, Dzh.I.Huseynov4 1D-r fiz.-mat. Sciences, Associate Professor, aydin60@inbox.ru; 2Candidate phys.-mat. Sciences, Associate Professor, 1959oktay@mail.ru; 3 Candidate phys.-mat. Sciences, Associate Professor, xatirafizik@mail.ru; 4D-r fiz.-mat. Sciences, Associate Professor, cih_58@mail.ru , Azerbaijan State Pedagogical University

Thin-film amorphous films are widely and successfully used in information recording and

display systems, solar energy, sensor technology, etc. One of the promising areas for further expanding the capabilities of this new class of semiconductors is the creation on their basis of “nano- crystalline media”, which are compositions of a large number of “crystals” of nano-meter dimensions

that form in the amorphous matrix at the initial stages of the crystallization process developing in it. The resulting nano-crystals are inherently atomic clusters that form not in the crystal lattice, but in an amorphous medium.

Keywords: amorphous films, atomic clusters, germanium monosulfide.

The purpose of this work was to study the effect of Nd atoms on the optical and electrical properties of amorphous germanium monosulfide films obtained by thermal spraying. The absorption spectrum was studied in the region of the absorption threshold, as well as the temperature dependence of the electrical conductivity of amorphous GeS and Ge1-xNdxS films (x = 0.005; 0.01). It has been established that during thermal spraying a homogeneous solid solution of Nd in GeS is not formed. Addition of Nd causes a tendency to clustering Nd-rich regions in the GeS matrix.

All measurements were performed on samples with a diameter of 10 mm. Ohmic contacts were created by soldering silver acid. Optical measurements were carried out on a set-up

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assembled base of the aperture monochromator MDR-2. X-ray phase analysis was performed on a D8 ADVANCE diffractometer.

Thermo-optical phenomena are observed in Ge1-xNdxS thin films, their role is enhanced with increasing Nd concentration. As the Nd content increases, the conductivity of the films increases, which leads to their Joule heating in an electric field, which causes thermal switching. However, based on the obtained data, it can be argued that the addition of Nd

leads to the appearance of new states associated with clusters in the band gap. The same states are responsible for the “shoulder” observed in optical absorption.

Along with the effect on the optical properties, the Nd impurity has a great influence on the electrical properties of thermally deposited Ge1-xNdxS films. It was found that the effect of Nd atoms on the physical properties of thin films is greatly enhanced by thermal annealing.

Measurements were carried out both when heated to a temperature close to the softening temperature Td, and during cooling. For amorphous films, the only values of activation energy for this technology of 0.75 eV films were given.

Thus, experiments conducted by us with thin amorphous films, thermal evaporation confirm:

1.Impurity atoms of rare earth elements (in this case, Nd) contribute to the formation of clusters in the amorphous matrix of germanium monosulfide.

2.Formed nanocrystals in an amorphous matrix lead to the appearance of new states in the band gap.

3.With an increase in the Nd content, the anisotropy of thin films decreases.

4.With an increase in the concentration of impurity atoms Nd, the conductivity of the films increases, which leads to heating, and ultimately to

thermal switching thin film.

5. The amorphous GeS matrix provides “comfortable” conditions for the formation of practically non-stressed clusters, where these amorphous films are widely used in systems for recording and displaying information.

Referenses

1.Milvidsky M.T., Chaldyshev V.V. Nanoscale atomic clusters in semiconductors - a new approach to the formation of material properties. // FTP. 1998. V.32. B.5. P.513-522.

2.Madatov R.S., Alekperov A.S., Magerramova J.A. The effect of some REEs (Nd, Sm, Gd) on the physicochemical properties of a GeS crystal. // Crystallography. 2015. T.60B.6.S.921-923.

3.Alekperov A.S., Mamedov I.M., Gasanov O.M. The effect of Nd atoms on the electrophysical properties of a layered single crystal GeS. // Radio Engineering. Ukrainian interdepartmental scientific and technical collection. Kharkov. 2014. B.178. P.59-63.

4.Alekperov A.S. Production of Ge1-xLnxS Monocrystals and Their Electrophysical and Photoelectrical Properties // Journal of Advances in Physics. 2015. V.10.№3.P. 2798-2801.

5.Madatov R.S., Alekperov A.S., Hasanov O.M. The effect of switching and memory in layered GeS crystals. // Applied Physics. 2015. №4. P.11-16.

UDC 537.9

ELECTRICAL RESISTIVITY AND SEEBECK COEFFICIENT OF THE COMPOSITES CONSISTING OF “Bi0.4Sb1.6Te3 (MATRIX) – SnSe (FILLER)”

M.N. Yaprintsev1, A.E. Vasil’ev2, O.N.Ivanov3, M.V. Zhezhu4 1Cand. phys. and math. sci., yaprintsev@bsu.edu.ru

2Post graduate student, 748070@bsu.edu.ru

3Dr. phys. and math. sci., prof., ivanov.oleg@bsu.edu.ru

3Post graduate student, 1214239@bsu.edu.ru Belgorod State University

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Composites consisting of “Bi0.4Sb1.6Te3 (matrix) – SnSe (filler)” with various weight content of filler (0, 10 and 20 wt. %) were prepared by spark plasma sintering method. With increasing the filler content, ρ was decreasing, whereas S is decreasing. In spite of such ρ and S degrading, thermal conductivity of the composites developed can be assumed to be low enough to compensate this degrading, resulting in improving in the thermoelectric efficiency.

Keywords: thermoelectric composite, spark plasma sintering, electrical resistivity, Seebeck coefficient.

Actual problem of material science is developing new semiconductor materials with enhanced thermoelectric efficiency, which is characterizing by the thermoelectric figure-of- merit, ZT. Lower thermal conductivity and specific electrical resistivity and higher Seebeck coefficient should be at the same time combined for effective thermoelectric material to reach higher ZT value. These thermoelectric properties are intimately but adversely inter-dependent: optimizing one often degrades the others. Tin chalcogenides due to their layered structures have rather low lattice thermal conductivity and acceptable electronic properties, which makes it possible to consider them as ones of the most promising candidates among potential high-performance thermoelectrics. But, owing to poor mechanical and high anisotropy in physical properties, practical application of these compounds is sufficiently limited. However, tin chalcogenides can be applied as fillers with low thermal conductivity to prepare the composites based on conventional thermoelectrics (bismuth telluride and bismuth telluride based

solid solutions with electron and hole conductivity). The aim of this work is (i) to prepare the composites consisting of “Bi0.4Sb1.6Te3 (matrix) – SnSe (filler)” with various weight ratios

between the matrix and filler, and (ii) to trace the composition effect on the specific electrical resistivity and Seebeck coefficient.

Figure. Temperature dependences of ρ, S and P for the composites with various compositions

Starting Bi0.4Sb1.6Te3 and SnSe powders were used to prepare the composites corresponding to different contents of filler (0, 10 and 20 wt. %). Spark plasma sintering (SPS) method by using a SPS-25/10 system was applied to compact powder mixture at pressure of 40 MPa, temperature 620 K and sintering time of 5 min and, hence, prepare bulk samples. X- ray diffraction (XRD) analysis of the bulk samples was performed by a Rigaku Ultima IV diffractometer with CuKα – radiation. The specific electrical resistivity, ρ, and the Seebeck coefficient, S, were measured by using a ZEM-3 system. According to the XRD pattern, the bulk samples consist of individual Bi0.4Sb1.6Te3 and SnSe subsystems, that is these samples are really composites. Besides, all the compositions were found to be highly textured. Due to this texturing, strong anisotropy in ρ and S, measured along directions parallel and perpendicular to the SPS-pressing direction, was found. These properties were found to be enhanced ones

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for the parallel orientation. With increasing the filler content, ρ was decreasing, whereas S is decreasing within whole temperature range, presented in Fig. Naturally, power factor, P, defined as P=S2/ρ is naturally decreasing. ρ is gradually increasing with increasing in measuring temperature for all the compositions, that is characteristic of degenerate semiconductors. Maxima observed in the S(T) curves are originated from a bipolar effect, when electrons and holes are simultaneously thermally generated in semiconductor due to intrinsic conductivity.

In spite of degrading in ρ and S in the composites developed, their thermal conductivity can be happened to be low enough to compensate this degrading, and, hence, to result in improving in the thermoelectric efficiency. The thermal conductivity measurements are in progress now.

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