Optical and Optoelectronic Properties of Bi2Te3, Sb2Te3, and Bi0.5Sb1.5Te3 Flakes

Abstract

In this study, a mechanical exfoliation method was developed for the synthesis of high purity Bi2Te3, Sb2Te3, and Bi0.5Sb1.5Te3 flakes. The synthesized Bi2Te3, Sb2Te3, and Bi0.5Sb1.5Te3 flakes were characterized by atomic force microscope, Raman spectroscopy, and photoluminescence (PL). The effect of the thickness of the Bi2Te3, Sb2Te3, and Bi0.5Sb1.5Te3 flakes on PL and Raman spectra was investigated. As the thickness increased in the Bi2Te3 flakes, the out of plane vibration mode (A21g) shows a blue shift. For the thicker Sb2Te3 flakes, the A11g and E2g modes indicated a blue shift and a red shift, respectively. When the thickness of Bi0.5Sb1.5Te3 flakes decreased, the in-plane vibration mode (E2g) shifted to lower frequencies. A new Raman peak has been observed in Bi0.5Sb1.5Te3 flakes, which is not active in the thin films. PL measurements of Bi0.5Sb1.5Te3 flakes with various thickness revealed PL peaks in the range of 2.15 - 2.54 eV at room temperature (300 K). A Bi0.5Sb1.5Te3 flakes-based photodetector exhibited photoresponsivity as high as 661.5 A/W at a 0.02 mW power density with an 1800 nm laser at room temperature (300 K). Compared to the optoelectronic properties of Bi2Te3 flake, a twice higher responsivity at a wavelength of 1800 nm was observed with the Bi0.5Sb1.5Te3 flake-based photodetector.