Effect of annealing on chemically deposited Bi2Se3–Sb2Se3 composite thin films

A room temperature chemical bath deposition (CBD) method was developed to deposit Bi2Se3–Sb2Se3 composite thin films. The preparative parameters such as concentration of bismuth ions, concentration of antimony ions, volume ratio of bismuth and antimony, complexing agent and deposition time were optimized to get good quality Bi2Se3–Sb2Se3 composite thin film of terminal thickness 0.34 μm. These films were annealed in air at 175 °C for 4 h. The effect of annealing on structural, optical and electrical properties were studied. The X-ray diffraction (XRD) study reveals that films are of Bi2Se3–Sb2Se3 composite with individual Bi2Se3 and Sb2Se3 phases. Scanning electron microscopy (SEM) study for as-deposited films showed that films are well covered to the substrate surface with some surface roughness as seen from atomic force microscopy (AFM) image of as-deposited films. The surface morphology of the film is smooth and homogeneous with nanocrystalline grain size. The optical bandgap is found to be 1.6 eV for Bi2Se3–Sb2Se3 composite thin film which lies between bandgaps of Bi2Se3 and Sb2Se3, and slightly decreases after annealing. The room temperature dark electrical resistivity for Bi2Se3–Sb2Se3 composite thin film is found to be of the order of 105 Ω cm with n-type electrical conductivity was confirmed from thermo-e.m.f. study.