Anton V. Suslov

Based on a thermodynamic ratio between the thermopower coefficient and entropy of the electrically conducting medium, we obtained an estimated value of the thermoelectric efficiency parameter ZT for an electronic system of fully ionised plasma. An example of such a system, which is in the most disordered state, is the electron-nuclear plasma of the Sun. The resulting universal value ZT = (25/6) can be considered as an assessment of the limiting capabilities of thermoelectric energy conversion. На основе термодинамического соотношения между коэффициентом термоэдс и энтропией электропроводящей среды для электронной системы полностью ионизованной плазмы, находящейся в наиболее неупорядоченном состоянии, природным примером которой может служить электронно-ядерная плазма Солнца, получено оценочное значение параметра термоэлектрической эффективности ZT, выражающееся универсальным числом ZT = (25/6), которое можно рассматривать как некоторую оценку предельных возможностей термоэлектрического преобразования энергии.

The paper is devoted to the study of transverse electric field effect on transport properties of charge carriers in bismuth and bismuth-antimony thin films. Experimental results reveal the existence of electric field effect in thin films of composition up to 12 at.% Sb. The dependencies of resistance on magnitude of electric field are obtained in a wide range of film thicknesses. A qualitative interpretation of the observed effect is given based on the analysis of the mobility of electrons and holes in films depending on the sign of the electric field and the film thickness. Работа посвящена исследованию влияния поперечного электрического поля на транспортные свойства носителей заряда в тонких пленках висмута и системы висмут-сурьма. В работе экспериментально подтверждено существование эффекта электрического поля в тонких пленках с содержанием сурьмы до 12 ат.%. Получены экспериментальные зависимости сопротивления от величины электрического поля для пленок разных толщин. Дана качественная интерпретация наблюдаемого эффекта на основе анализа подвижности электронов и дырок в пленках в зависимости от знака напряжённости электрического поля и толщины образцов.

Уникальные свойства висмута и системы висмут-сурьма привлекают все более внимание исследователей в области стрейнтроники и деформационной инженерии в двухмерных материалах в последние десятилетия. В рамках данной работы была проведена апробация исследования удельного сопротивления пленок висмута на подложках из боросиликатного стекла и кремния деформированных методом купольного изгиба. Полученные результаты хорошо согласуются с результатами исследования пленок, деформированных другими методами, и может быть применен для моделирования плоскостной деформации пленки. Учитывая использование двух подложек, метод позволяет получить возможность получения непрерывных зависимостей свойств пленок от деформации в диапазоне до 0,8 % (относительного изменения площади) при комнатной температуре.

2D materials with van der Waals (vdW) gaps between covalently bonded blocks are in the focus of modern semiconductor science and technology. Of special interest is the possibility to control their properties through the vdW gap reconfiguration. Herein, using first‐principles simulations it is demonstrated that uniaxial compression of GaSe, counterintuitively, does not serve to close the gap but, instead, changes the dimensionality from 2D to quasi‐1D, with flat GaSe chains oriented along the applied pressure. The structural change is accompanied by drastic changes in electronic structure. The inability to close the vdW gap to the antibonding nature of Se–Se interactions is attributed.

The increasing of charge carriers concentration in thin bismuth films

The study of the electronic properties of ultrathin films of pure bismuth and bismuth-antimony alloys is of interest, since an increase in conductivity with decreasing sample thickness was found. This paper presents the results of an experimental study of the structure, electrical, galvanomagnetic and thermoelectric properties of pure bismuth and Bi_1-xSb_x thin films (x=0.05 and 0.12) on a mica substrate in the thickness range of 10-30 nm. An increase in the conductivity with a decrease in the thickness of the samples was found. It may be due to the presence of topologically protected surface states. It is shown that the features of the manifestation of this effect are significantly influenced by the alloys band structure. The form of the temperature dependences of the Seebeck coefficient casts doubt on the fact that surface states have a positive effect on the thermoelectric efficiency of thin bismuth-antimony films. However, the detection of a positive thermoelectric power in Bi_0.88Sb_0.12 samples can become an important factor for searching for the possibility of creating a p-branch of thermoelectric converters. Keywords: bismuth, antimony, thin films, surface states, thermoelectric power.

This paper presents the results of studying the magnitude of the strain of semimetal films created by the dome bending of the substrate. The deformation is controlled by X-ray diffraction (XRD) analysis. It is shown that the dome bending method can be used to study films under conditions of the in-plane deformation that occurs in the film-substrate system due to the difference in the coefficients of thermal expansion of the film and substrate material. It is established that the deformation created by the dome bending of the substrate in combination with the use of substrates with a different thermal expansion makes it possible to obtain a relative in-plane deformation of bismuth films up to 0.8% at 300 K.

The reasons for increasing the charge carriers concentration in thin bismuth films are discussed. The concentration was calculated on the basis of the measured electrical and galvanomagnetic coefficients at the temperature 77K under the two-band approximation and the assumption that the charge carriers free path in the film is isotropic.