Ni-doped Bi0.5Sb1.5Te3 single crystal: a potential functional material for thermoelectricity, topological insulator, and optoelectronics

We report the growth of Ni-doped Bi0.5Sb1.35Ni0.15Te3 single crystal via the self-flux method. The crystalline nature of a grown single crystal was confirmed by the X-ray diffraction technique (XRD). Interestingly, the XRD pattern shows a sharp reflections of < 0 0 l > type of planes, revealing the growth of the crystal in c-direction. The grown single crystal was subjected for measurement of field dependence magnetization at 300 K and temperature-dependent magnetic moment. The electronic transport property of bulk single crystal was also carried out in a wide range of temperatures from 150 to 450 K. Reasonably large electrical conductivity sigma similar to 1584 S/cm at room temperature was observed which shows similar to 400% enhancement in sigma than the electrical conductivity of bare Bi0.5Sb1.5Te3 single crystal (400 S/cm at 300 K). This enhanced electrical conductivity results to significant power factor similar to 1.68 x 10(- 3)W/m K(2)at 300K which is 163% larger than that of bare Bi0.5Sb1.5Te3 single crystal (6.45 x 10(- 4)W/m K-2). Magnetic properties of a single crystal of Bi0.5Sb1.35Ni0.15Te3 reveal ferromagnetic behavior at 300 K. The photoluminescence (PL) behavior of Bi0.5Sb1.35Ni0.15Te3 single-crystal was also scrutinized. The PL spectra of Bi0.5Sb1.35Ni0.15Te3 single crystal shows the strong red emission peak in the visible region from 600 to 690 nm upon excitation at 375 nm wavelength, which corresponds to the optical bandgap of 2.1 eV.