화학공학소재연구정보센터
Journal of Crystal Growth, Vol.483, 216-222, 2018
MOVPE growth and transport characterization of Bi2-xSbxTe3-ySey films
We present a first study of films of the quaternary Bi2-xSbxTe3-ySey solid solutions on (0001) sapphire substrates grown by atmospheric pressure MOVPE. Trimethylbismuth, trimethylantimony, diisopropy-lselenide and diethyltelluride were used as precursors. To passivate the free bonds of the substrate and to improve the epitaxy, a thin (15 nm) ZnTe buffer layer was first grown. EDX analysis of the films grown at a temperature of 445 degrees C and about 10-fold excess of chalcogen in the vapor phase indicates on their compliance with V2VI3 stoichiometry. AFM and SEM investigations showed that at the initial stage of deposition the Stranski-Krastanov growth mode is dominant. Complete coalescence of nanoislands occurs at a thickness about 60 nm and further film formation is in the 2D layer-by-layer growth mode. A high mole fraction of antimony in the vapor phase leads to bad crystalline quality of the films and even to their discontinuity. Transport properties of the Bi2-xSbxTe3-ySey films were evaluated using Van der Pauw Hall effect measurements in the range of temperatures of 10-300 K. Some films are always n- or p-type; in other samples the change of conductivity from p-to n-type was observed when the temperature decreases. (C) 2017 Elsevier B.V. All rights reserved.