Growth and characterization of Bi2-xSbxTe3 (x=0-0.2) single crystals

Bismuth telluride is a well known V-VI group intermetallic compound semiconductor. Its narrow band gap, 0.16 eV, makes it suitable for application in thermoelectric devices. Its crystal growth and thin film studies have been well reported. Antimony doping in Bi2Te3 has been studied for its effect on its basic semiconducting, optoelectronic and thermoelectric properties. The authors report here on the crystal growth (zone-melting) and band gap of Bi2-xSbxTe3. The compositions studied are Bi2-xSbxTe3 (x=0-0.2). The freezing interface temperature gradient of 50 °C/cm has been found to yield the best quality crystals obtainable at the growth rate of 0.35 cm/h. The growth features on the free surfaces of crystals have been observed to be of typical character assigned to the crystal symmetry. The crystals have been characterized using XRD technique. FTIR spectra were obtained and used to evaluate the band gap which is found to be of direct type. The paper reports the detailed results.