Univerzita Pardubice Fakulta chemicko- technologická

Univerzita Pardubice

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Publikace detail

Native Defects in SnSe and their Temperature Dependence

Autoři: Šraitrová Kateřina | Holý Václav | Kucek Vladimír | Drašar Čestmír

Rok: 2018

Druh publikace: ostatní - přednáška nebo poster

Strana od-do: nestránkováno

Tituly:

Jazyk	Název	Abstrakt	Klíčová slova
eng	Native Defects in SnSe and their Temperature Dependence	SnSe has been recently studied as a promising thermoelectric material, especially for its high values of figure of merit (ZT = 2.6 at 923 K) and very low values of thermal conductivity1. It has been shown that SnSe is very vivid material. Its physical properties depend not only on temperature history of the sample, but also on the current temperature at which the measurement is performed. Most likely, the results depend on measurement kinetics as well. This produces discrepancies in results of individual research groups. This makes even the utilization of theoretical calculations of formation energy of native point defects questionable. From the literature sources, it is not clear what native defects should be dominant in the structure. Sn vacancies, Se vacancies, Se interstitial defects are mostly discussed. Some of them were even directly observed2,3. Based on other works it follows that no point defects are present, but foreign phase SnSe2 is observed4. In order to examine presence of native defects in SnSe and their temperature dependence, a series of single crystals was prepared. These single crystals were annealed for a long period at desired temperature. Afterwards, they were quenched at room temperature. Prepared samples were characterized by high resolution X-ray diffraction (HR XRD), electrical conductivity, Hall coefficient and Seebeck coefficient. These parameters were measured over a temperature range 93 – 473 K. HR XRD results suggest presence of Sn or Se vacancies in the structure next to secondary SnSe2. From our results of transport measurements it follows that at temperatures above 300 °C the concentration of defects steeply increases while at temperatures below 300 °C the compound approaches absolutely stoichiometric structure with very low concentration of defects. This corresponds with low concentration of holes (< 2x1017cm-3). This characteristic is indisputably connected with second order phase transition and stoichiometry variations with temp