Microstructural characterization of Bi 2 Te 3 thin films prepared by hot wall epitaxy

The influence of growth conditions on the microstructures of Bi 2 Te 3 films grown on (111) and (100)-oriented GaAs substrates by hot wall epitaxy is investigated using X-ray diffraction, scan electron microscopy, energy dispersive spectrum, high resolution transmission electron microscopy and micro-Raman spectroscopy. It is found that high quality Bi 2 Te 3 thin films with c-axis oriented are prepared when the temperatures of the Bi 2 Te 3 source and (111) GaAs substrate are 505°C and 375°C respectively. The low substrate temperature and the crystal symmetry mismatch between the (100) GaAs substrate and Bi 2 Te 3 epitaxial film make the crystalline grains mis-oriented, which are responsible for the degradation of the crystal quality of Bi2Te3 films. In addition, the low substrate temperature could lead to the non-stoichiometry.