Growth of Bi₂Se₃ Films by Chemical Bath Deposition at Room Temperature

Abstract

Bismuth selenide (Bi_xSe_y) films are deposited onto glass substrate using chemical bath deposition at room temperature. The reacting bath contained bismuth nitrate, triethanolamine and sodium selenosulfate as selenium (Se) source. Ammonium hydroxide is used to adjust the pH of the bath. The films deposited in solutions containing Se source solution of 10 ml and 15 ml are characterized by surface morphological, compositional and structural, properties. The optimum deposition time is about 3 hours for both solutions. Films deposited up to 24 hours in bath with 10 ml Se source solution had thickness ranging up to 232 nm. The deposition rate is found to increase up to 61 nm/h for 3-hour deposition. In the case of bath with 15 ml Se source solution, the film thickness ranged from 45 nm to 632 nm for 1-hour to 24-hour deposition, respectively; with a deposition rate increasing up to 123 nm/h for 3-hour deposition. Film roughness of about 6.6 nm to 22.8 nm is measured by atomic force microscope for films deposited in bath containing 10 mL Se source and 15 ml of Se source, respectively. Crack free layers are observed with randomly large plate-like particles on top of the layer for some films. The films with typical composition of Bi_21.8Se_78.2 are found to be rich in Se when deposited for 6 hours, whereas the composition of a film deposited in the same bath (10 mL Se source) for 3 hours is found at Bi_60.3Se_39.6. Additionally, structural analysis performed by x-ray diffraction (XRD) did not reveal well-defined XRD patterns, which indicates that Bi_xSe_y films were constituted mostly of nanocrystalline grains.