NANOSIZED STRUCTURES IN PbTe MATRIX WITH CdSe IMPURITIES

В работе проведены электронно-микроскопические исследования полупроводниковых соединений на основе PbTe с примесями дисперсных фаз CdSe. Как показали результаты исследования, в исходном нелегированном соединении PbTe содержание атомов свинца составляет около 63,8 вес%, а содержание теллура составляет 36,2 вес%, т.е. соответствует стехиометрическому составу. Согласно изображениям электронного микроскопа, эти компоненты равномерно распределены по площади. Результаты исследования также показали, что образующиеся новые фазы имеют размеры зерен от 90 нм до 2 мкм. Полученные значения параметра решетки для соединения теллурида свинца и сингония хорошо согласуются с литературными данными. Структура образующихся фаз имеет такую же симметрию, как и исходное нелегированное соединение PbTe, гранецентрированную кубическую решетку с классом симметрии Fm3m. В молекулах новых образующихся фаз, в которых преобладают содержания элементов Cd и Se, обнаружено изменение сингонии кристаллической решетки. In this work, electron microscopic studies of semiconductor compounds based on PbTe with impurities of dispersed CdSe phases have been carried out. As shown by the research results, in the initial undoped PbTe compound, the content of lead atoms is about 63,8 wt.%, and the tellurium content was 36,2 wt.%, i.e. corresponded to the stoichiometric composition. According to the electron microscope images, these components are evenly distributed over the area. The results of the study also showed that the formed new phases had grain sizes from 90 nm to 2 pm. The obtained values of the lattice parameter for the lead telluride compound and crystal system are in good agreement with the literature data. The structure of the resulting phases has the same symmetry as the initial undoped PbTe compound, a face-centered cubic lattice with the Fm3m symmetry class. In the molecules of the newly formed phases, in which the abundances of the elements Cd and Se prevailed, a change in the crystal lattice syngony was found.

Structural complexity and the metal-to-semiconductor transition in lead telluride

Lead chalcogenides are known for their thermoelectric properties since the first work of Thomas Seebeck on the discovery of this phenomenon. Yet, the electronic properties of lead telluride are still of interest due to the incomplete understanding of the metal-to-semiconductor transition at temperatures around 230 °C. Here, a temperature-dependent atomic-resolution transmission electron microscopy study performed on a single crystal of lead telluride reveals structural reasons for this electronic transition. Below the transition temperature, the formation of a dislocation network due to shifts of the NaCl-like atomic slabs perpendicular to {100} was observed. The local structure modification leads to the appearance of in-gap electronic states and causes metal-like electronic transport behavior. The dislocation network disappears with increasing temperature, yielding semiconductor-like electrical conductivity, and re-appears after cooling to room temperature restoring the metal-like behavior. The structural defects coupled to the ordering of stereochemically active lone pairs of lead atoms are discussed in the context of dislocations' formation.

Heat transport through propagon-phonon interaction in epitaxial amorphous-crystalline multilayers

Managing heat dissipation is a necessity for nanoscale electronic devices with high-density interfaces, but despite considerable effort, it has been difficult to establish the phonon transport physics at the interface due to a “complex” interface layer. In contrast, the amorphous/epitaxial interface is expected to have almost no “complex” interface layer due to the lack of lattice mismatch strain and less associated defects. Here, we experimentally observe the extremely-small interface thermal resistance per unit area at the interface of the amorphous-germanium sulfide/epitaxial-lead telluride superlattice (~0.8 ± 4.0 × 10‒9 m2KW−1). Ab initio lattice dynamics calculations demonstrate that high phonon transmission through this interface can be predicted, like electron transport physics, from large vibron-phonon density-of-states overlapping and phonon group velocity similarity between propagon in amorphous layer and “conventional” phonon in crystal. This indicates that controlling phonon (or vibron) density-of-states and phonon group velocity similarity can be a comprehensive guideline to manage heat conduction in nanoscale systems.

A review on the development of conjugated polymer-based textile thermoelectric generator

Thermoelectric (TE) materials based on conjugated/conductive polymers can directly convert heat into electricity, and thus found promising applications in energy scavenging and cooling technologies. The performance of these thermoelectric materials is governed by different parameters like the nature of the material, thermal stability, electrical conductivity, Seebeck coefficient, and thermal conductivity. Although the traditional inorganic semiconductor materials such as PbTe (Lead Telluride), Bi2Te3 (Bismuth Telluride), SiGe (Silicon-Germanium), SnSe (Tin Selenide), and Skutterudite (CoAs2) are giving high performance, they have some inherent limitations, such as poor processability, toxicity, rare availability, and high cost of manufacturing. Whereas, organic conjugated polymers such as polyacetylene (PA), polyaniline (PANi), Poly(3-hexylthiophene) (P3HT), polypyrrole (PPy), poly 3,4-ethylenedioxythiophene (PEDOT), etc. have low cost of synthesis, light in weight, low toxicity and better processibility. Organic textile thermoelectric generators (T-TEG) can be prepared by in-situ polymerization of the conjugated polymers onto textile substrates. This article reviews the preparation, design and performance of these T-TEGs. Various approaches and scopes of improvement of efficiency of the thermoelectric effect of the T-TEGs are discussed. Various potential applications of the T-TEG in different fields are also described.