Samir Gahramanov - Academia.edu (original) (raw)

Papers by Samir Gahramanov

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques, 2021

Qualitative changes in the nature of the surface electronic structure during potassium K adsorpti... more Qualitative changes in the nature of the surface electronic structure during potassium K adsorption on the (0001) surface of Bi2Se3 and Bi2Te3 crystals are found. In the early stages of adsorption, there is no change in the type of surface conductivity. The K/Bi2Se3 and K/Bi2Te3 interfaces retain their qualitative characteristics until a saturation coating. In the region of the saturation coating, a surface transition to a state with opposite bending of the bands is observed. After adsorption, the images of the (0001) surface of Bi2Se3 and Bi2Te3 show pyramidal formations and quasi-one-dimensional linear bands. Periodic bulges represented by strips lead to a smoothly varying periodic potential, which is responsible for the capture of carriers in one-dimensional potential wells and a shift in the bands of the bulk and surface states. These structures are interesting as a practical implementation of a one-dimensional quantum wire and can potentially be used to achieve 1D dissipation-free transport.

Low Temperature Physics, 2003

Effect of Potassium Adsorption on the Surface Properties of Bi2Se3 and Bi2Te3 Crystals, 2022

Qualitative changes in the nature of the surface electronic structure during potassium K adsorpti... more Qualitative changes in the nature of the surface electronic structure during potassium K adsorption on the (0001) surface of Bi 2 Se 3 and Bi 2 Te 3 crystals are found. In the early stages of adsorption, there is no change in the type of surface conductivity. The K/Bi 2 Se 3 and K/Bi 2 Te 3 interfaces retain their qualitative characteristics until a saturation coating. In the region of the saturation coating, a surface transition to a state with opposite bending of the bands is observed. After adsorption, the images of the (0001) surface of Bi 2 Se 3 and Bi 2 Te 3 show pyramidal formations and quasi-one-dimensional linear bands. Periodic bulges represented by strips lead to a smoothly varying periodic potential, which is responsible for the capture of carriers in onedimensional potential wells and a shift in the bands of the bulk and surface states. These structures are interesting as a practical implementation of a one-dimensional quantum wire and can potentially be used to achieve 1D dissipation-free transport.

IMPURITY TYPE INFLUENCE ON SHAPE OF INTERLAYER NANOSTRUCTURES IN BISMUTH CHALCOGENIDES, 2022

Materials with arrays of nanoislands of various sizes and distribution densities have been obtain... more Materials with arrays of nanoislands of various sizes and distribution densities have been obtained. The formation mechanism of the above nanostructures is described, which is associated with migration, coalescence, and clustering in the interlayer space of impurity not dissolved in the layers and a superstoichiometric excess.

Inorganic Materials, 2012

ABSTRACT The (0001) surface morphology of Bi2Te3〈M〉 (M = Cu, Ni) layered crystals has been studie... more ABSTRACT The (0001) surface morphology of Bi2Te3〈M〉 (M = Cu, Ni) layered crystals has been studied using atomic force microscopy (AFM) and scanning electron microscopy. Two- and three-dimensional AFM images reveal charge transport paths through inhomogeneities created by nanostructured elements (5–20 nm) in the Te(1)-Te(1) interlayer spaces. The nanoparticle distribution in the (0001) plane is similar to the arrangement of model two-dimensional percolation clusters on a square lattice. The carrier mobility in Bi2Te3〈0.5 wt % Ni〉 crystals varies anomalously between 80 and 120 K.

Inorganic Materials, 2009

THE FERMI LEVEL TUNING BY ANNEALING IN SELENIUM VAPOR AND ARGON PLASMA ETCHING OF Bi2Se3 SURFACES, 2021

In the near-surface area of Bi2Se3 crystals, in order to reduce concentration of charge carriers ... more In the near-surface area of Bi2Se3 crystals, in order to reduce concentration of charge carriers and Se vacancies, which are electronic donors, annealing in selenium vapor was used. It has been established that the most optimal mode is annealing at a temperature of 100-150 °C for 70 hours. Effective impact on the surface condition with an identical purpose is exerted by processing the sample in a glow discharge in an argon medium. It was determined that treatment with an ions dose of ~1,1•10 17 ion/cm-2 , both after and without preliminary treatments in the form of annealing or chemical etching, leads to a significant decrease in concentration of carriers in crystals near-surface area.

Bi 2 Te 3-х Se x 〈Ag〉 (х = 0.04) nanocrystal formation Abstract. The results of experimental rese... more Bi 2 Te 3-х Se x 〈Ag〉 (х = 0.04) nanocrystal formation 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 Bi 2 Te 3-х Se x 〈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 Bi 2 Te 3-х Se x 〈Ag〉 crystal images with nanolayers were obtained. Being based on experimental data, the fractal dimension of nanocrystalline layers was estimated.

The modern positions on the directed designing of supramolecular systems have been considered on ... more The modern positions on the directed designing of supramolecular systems have been considered on the bases: - Layered misfit compounds, - clathrates and silicates with frame structures, - layered hydroxides, - layered structures with variable size of structural planes, - layered compounds with variable size of structural cavities with “guests” of different size in “master” lattice, - matrix crystals. It is shown that the sizes and forms of matrix molecules and “guest” (cluster) molecules play the important role in the organization of the regularities of suprastructure layered misfit compounds, clathrate compounds and silicates with frame structures, different intercalated layered compounds and hydroxides. It is established, that nonvalency chalcogen-chalcogen interactions play the special role in the creation of the supramolecular chalcogenide clusters

The Bi2(Te0.9Se0.1)3 solid solutions thin films are produced by “hot wall” thermal evaporation in... more The Bi2(Te0.9Se0.1)3 solid solutions thin films are produced by “hot wall” thermal evaporation in vacuum. From the data of X-ray diffraction studies, atomic-force microscopy of the surface relief, and Raman spectroscopy, it is established that vacuum thermal annealing at a temperature of 200°C for 1 h substantially increases the degree of film crystallization. The laser radiation excitation power optimal for studies of the Raman spectra of the Bi2(Te0.9Se0.1)3 films is determined.

The electron-microscopic images and roentgen-diffractometer fotos in Bi2Te3 and Sb2Te3 layered sy... more The electron-microscopic images and roentgen-diffractometer fotos in Bi2Te3 and Sb2Te3 layered systems show, that Те(1)-Те(1) gap plays nano-reactor role. The origination, self-organization and formation of quazi-two-dimensional layers with nano-islands, nano-rods and nano-crystals take place in such nano-reactors. These structural blank spaces – nano-reactors – are filled by compounds, the following modification of which leads to nano-crystal formation, for example, in Bi2Te3 : CuTe, Cu2Te, Cu64O, Cu0,647Te0,353; in Sb2Te3 : B2О, BiBO3, Bi2B8O15.

Исследованы температурные зависимости (диапазон температур T = 0.5−300 K) удельного сопротивления... more Исследованы температурные зависимости (диапазон температур T = 0.5−300 K) удельного сопротивления в плоскости слоев и в направлении, перпендикулярном слоям, а также гальваномагнитные эффекты в нелегированных и легированных монокристаллах Bi 2 Te 3 (магнитное поле H < 80 кЭ, T = 0.5−4.2 K). Показано, что при легировании Bi 2 Te 3 атомами III группы (индием и бором) анизотропия проводимости повышается главным образом за счет увеличения удельного сопротивления в направлении, перпендикулярном слоям. Это позволяет предположить, что атомы этих примесей при легировании в основном внедряются в ван-дер-ваальсовы щели между слоями. Выявлено также, что при легировании Bi 2 Te 3 индием и бором температурная зависимость подвижности ослабляется, что свидетельствует о повышении в механизмах рассеяния роли процессов рассеяния носителей на дефектах. Оценены величины концентраций и подвижностей носителей заряда, значения холл-фактора, обусловленного анизотропией эффективных масс и ориентацией эллипсоидов относительно кристаллографических осей, площади экстремального сечения поверхности Ферми плоскостью, перпендикулярной направлению магнитного поля, и энергии Ферми.

It is established that introduction of iron atoms between Bi2Te3 cleavage planes with Van der Waa... more It is established that introduction of iron atoms between Bi2Te3 cleavage planes with Van der Waals forces leading to chemical bond intensification between quintets and strengthening of Bi2Te3 takes place. Moreover, the interlayer nano-structures form growing perpendicularly to (0001) Bi2Te3 surface. Probably the interlayer ferromagnetic iron nano-structures are responsible for transition into ferromagnetic state and anomalous Hall effect (and thermo-e.m.f.) in Bi2-xFexTe3 alloys [1].

The considered review and clathratus analysis of misfit eutectic compounds PbTe(PbS)-NiSb, layere... more The considered review and clathratus analysis of misfit eutectic compounds PbTe(PbS)-NiSb, layered chalcogenides allows to (1) …). These structures can be related to the compound parts of supramolecular ensemble, where Bi 2 Te 3 frame is in the capacity of master for the fascinated atoms-guests (Cu, Ni, Sn, S, Nb and B). Probably, the layered structure Bi 2 Te 3 can be formed in clathratusoforming system with nano-structural fragments.

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques, 2021

Qualitative changes in the nature of the surface electronic structure during potassium K adsorpti... more Qualitative changes in the nature of the surface electronic structure during potassium K adsorption on the (0001) surface of Bi2Se3 and Bi2Te3 crystals are found. In the early stages of adsorption, there is no change in the type of surface conductivity. The K/Bi2Se3 and K/Bi2Te3 interfaces retain their qualitative characteristics until a saturation coating. In the region of the saturation coating, a surface transition to a state with opposite bending of the bands is observed. After adsorption, the images of the (0001) surface of Bi2Se3 and Bi2Te3 show pyramidal formations and quasi-one-dimensional linear bands. Periodic bulges represented by strips lead to a smoothly varying periodic potential, which is responsible for the capture of carriers in one-dimensional potential wells and a shift in the bands of the bulk and surface states. These structures are interesting as a practical implementation of a one-dimensional quantum wire and can potentially be used to achieve 1D dissipation-free transport.

Low Temperature Physics, 2003

Effect of Potassium Adsorption on the Surface Properties of Bi2Se3 and Bi2Te3 Crystals, 2022

Qualitative changes in the nature of the surface electronic structure during potassium K adsorpti... more Qualitative changes in the nature of the surface electronic structure during potassium K adsorption on the (0001) surface of Bi 2 Se 3 and Bi 2 Te 3 crystals are found. In the early stages of adsorption, there is no change in the type of surface conductivity. The K/Bi 2 Se 3 and K/Bi 2 Te 3 interfaces retain their qualitative characteristics until a saturation coating. In the region of the saturation coating, a surface transition to a state with opposite bending of the bands is observed. After adsorption, the images of the (0001) surface of Bi 2 Se 3 and Bi 2 Te 3 show pyramidal formations and quasi-one-dimensional linear bands. Periodic bulges represented by strips lead to a smoothly varying periodic potential, which is responsible for the capture of carriers in onedimensional potential wells and a shift in the bands of the bulk and surface states. These structures are interesting as a practical implementation of a one-dimensional quantum wire and can potentially be used to achieve 1D dissipation-free transport.

IMPURITY TYPE INFLUENCE ON SHAPE OF INTERLAYER NANOSTRUCTURES IN BISMUTH CHALCOGENIDES, 2022

Materials with arrays of nanoislands of various sizes and distribution densities have been obtain... more Materials with arrays of nanoislands of various sizes and distribution densities have been obtained. The formation mechanism of the above nanostructures is described, which is associated with migration, coalescence, and clustering in the interlayer space of impurity not dissolved in the layers and a superstoichiometric excess.

Inorganic Materials, 2012

ABSTRACT The (0001) surface morphology of Bi2Te3〈M〉 (M = Cu, Ni) layered crystals has been studie... more ABSTRACT The (0001) surface morphology of Bi2Te3〈M〉 (M = Cu, Ni) layered crystals has been studied using atomic force microscopy (AFM) and scanning electron microscopy. Two- and three-dimensional AFM images reveal charge transport paths through inhomogeneities created by nanostructured elements (5–20 nm) in the Te(1)-Te(1) interlayer spaces. The nanoparticle distribution in the (0001) plane is similar to the arrangement of model two-dimensional percolation clusters on a square lattice. The carrier mobility in Bi2Te3〈0.5 wt % Ni〉 crystals varies anomalously between 80 and 120 K.

Inorganic Materials, 2009

THE FERMI LEVEL TUNING BY ANNEALING IN SELENIUM VAPOR AND ARGON PLASMA ETCHING OF Bi2Se3 SURFACES, 2021

In the near-surface area of Bi2Se3 crystals, in order to reduce concentration of charge carriers ... more In the near-surface area of Bi2Se3 crystals, in order to reduce concentration of charge carriers and Se vacancies, which are electronic donors, annealing in selenium vapor was used. It has been established that the most optimal mode is annealing at a temperature of 100-150 °C for 70 hours. Effective impact on the surface condition with an identical purpose is exerted by processing the sample in a glow discharge in an argon medium. It was determined that treatment with an ions dose of ~1,1•10 17 ion/cm-2 , both after and without preliminary treatments in the form of annealing or chemical etching, leads to a significant decrease in concentration of carriers in crystals near-surface area.

Bi 2 Te 3-х Se x 〈Ag〉 (х = 0.04) nanocrystal formation Abstract. The results of experimental rese... more Bi 2 Te 3-х Se x 〈Ag〉 (х = 0.04) nanocrystal formation 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 Bi 2 Te 3-х Se x 〈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 Bi 2 Te 3-х Se x 〈Ag〉 crystal images with nanolayers were obtained. Being based on experimental data, the fractal dimension of nanocrystalline layers was estimated.

The modern positions on the directed designing of supramolecular systems have been considered on ... more The modern positions on the directed designing of supramolecular systems have been considered on the bases: - Layered misfit compounds, - clathrates and silicates with frame structures, - layered hydroxides, - layered structures with variable size of structural planes, - layered compounds with variable size of structural cavities with “guests” of different size in “master” lattice, - matrix crystals. It is shown that the sizes and forms of matrix molecules and “guest” (cluster) molecules play the important role in the organization of the regularities of suprastructure layered misfit compounds, clathrate compounds and silicates with frame structures, different intercalated layered compounds and hydroxides. It is established, that nonvalency chalcogen-chalcogen interactions play the special role in the creation of the supramolecular chalcogenide clusters

The Bi2(Te0.9Se0.1)3 solid solutions thin films are produced by “hot wall” thermal evaporation in... more The Bi2(Te0.9Se0.1)3 solid solutions thin films are produced by “hot wall” thermal evaporation in vacuum. From the data of X-ray diffraction studies, atomic-force microscopy of the surface relief, and Raman spectroscopy, it is established that vacuum thermal annealing at a temperature of 200°C for 1 h substantially increases the degree of film crystallization. The laser radiation excitation power optimal for studies of the Raman spectra of the Bi2(Te0.9Se0.1)3 films is determined.

The electron-microscopic images and roentgen-diffractometer fotos in Bi2Te3 and Sb2Te3 layered sy... more The electron-microscopic images and roentgen-diffractometer fotos in Bi2Te3 and Sb2Te3 layered systems show, that Те(1)-Те(1) gap plays nano-reactor role. The origination, self-organization and formation of quazi-two-dimensional layers with nano-islands, nano-rods and nano-crystals take place in such nano-reactors. These structural blank spaces – nano-reactors – are filled by compounds, the following modification of which leads to nano-crystal formation, for example, in Bi2Te3 : CuTe, Cu2Te, Cu64O, Cu0,647Te0,353; in Sb2Te3 : B2О, BiBO3, Bi2B8O15.

Исследованы температурные зависимости (диапазон температур T = 0.5−300 K) удельного сопротивления... more Исследованы температурные зависимости (диапазон температур T = 0.5−300 K) удельного сопротивления в плоскости слоев и в направлении, перпендикулярном слоям, а также гальваномагнитные эффекты в нелегированных и легированных монокристаллах Bi 2 Te 3 (магнитное поле H < 80 кЭ, T = 0.5−4.2 K). Показано, что при легировании Bi 2 Te 3 атомами III группы (индием и бором) анизотропия проводимости повышается главным образом за счет увеличения удельного сопротивления в направлении, перпендикулярном слоям. Это позволяет предположить, что атомы этих примесей при легировании в основном внедряются в ван-дер-ваальсовы щели между слоями. Выявлено также, что при легировании Bi 2 Te 3 индием и бором температурная зависимость подвижности ослабляется, что свидетельствует о повышении в механизмах рассеяния роли процессов рассеяния носителей на дефектах. Оценены величины концентраций и подвижностей носителей заряда, значения холл-фактора, обусловленного анизотропией эффективных масс и ориентацией эллипсоидов относительно кристаллографических осей, площади экстремального сечения поверхности Ферми плоскостью, перпендикулярной направлению магнитного поля, и энергии Ферми.

It is established that introduction of iron atoms between Bi2Te3 cleavage planes with Van der Waa... more It is established that introduction of iron atoms between Bi2Te3 cleavage planes with Van der Waals forces leading to chemical bond intensification between quintets and strengthening of Bi2Te3 takes place. Moreover, the interlayer nano-structures form growing perpendicularly to (0001) Bi2Te3 surface. Probably the interlayer ferromagnetic iron nano-structures are responsible for transition into ferromagnetic state and anomalous Hall effect (and thermo-e.m.f.) in Bi2-xFexTe3 alloys [1].

The considered review and clathratus analysis of misfit eutectic compounds PbTe(PbS)-NiSb, layere... more The considered review and clathratus analysis of misfit eutectic compounds PbTe(PbS)-NiSb, layered chalcogenides allows to (1) …). These structures can be related to the compound parts of supramolecular ensemble, where Bi 2 Te 3 frame is in the capacity of master for the fascinated atoms-guests (Cu, Ni, Sn, S, Nb and B). Probably, the layered structure Bi 2 Te 3 can be formed in clathratusoforming system with nano-structural fragments.

Proceedings of the 7th International Conference MTP-2021: Modern Trends in Physics, 2021

It is shown that the anomalies observed in the temperature dependence of the crystal lattice para... more It is shown that the anomalies observed in the temperature dependence of the crystal lattice parameters and kinetic parameters of bismuth telluride doped with copper and indium Bi2Te3<In,Cu> are explained by changes in the chemical bond and the effect of defect centers. The redistribution of the electron density between the metal and the central chalcogen layer in the quintet-layer of the crystal framework, in a certain temperature range, leads to a negative thermal coefficient of linear expansion (TCLE). The polarity of the covalent bond and the decrease in the Bi-Те(2) interatomic distances are directly affected by the magnitude of the interlayer interaction. The energy of thermal motion, when approaching the value of the energy of interlayer interaction, leads to deviation of bonds and to fluctuations in the distribution of electron density in the volume of the crystal.

XV RUSSIAN CONFERENCE ON SEMICONDUCTOR PHYSICS, 2022

We observed magnetoresistance oscillations at 249 K and 273 K in Bi2Te3 single crystals with quas... more We observed magnetoresistance oscillations at 249 K and 273 K in Bi2Te3 single crystals with quasi-two-dimensional layers separated by interlayer elements. The oscillation period is presumably related to the presence of two close-frequency Shubnikov–de Haas oscillations with an energy shift about 0.15 meV.