Optical and Structural Properties of Indium Doped Bismuth Selenide Thin Films

摘要

In: Bi_2Se_3 crystals were grown by Bridgman method at a growth velocity of 0.5cm/h with temperature gradient of 650 C/cm in our laboratory. The thin films of In:Bi_2se_3 were grown on amorphous substrate (glass) at a room temperature under a pressure of 10~(-4)Pa by thermal evaporation technique. Thin film were deposited at various thicknesses and optical absorption spectrum of such thin films, obtain in wave no. range 300 to 2600 cm~(-1). The optical energy gap calculated from this data were found to be inverse function of square of thickness, particularly for thickness about 1800 A or less. This dependence is explained in terms of quantum size effect. For thicker films, the bandgap is found to be independent of film thickness. For the surface stud of the as grown thin film by using AFM, which shows continuous film with some step height and surface roughness found in terms of few nm and particle size varies with respect to thickness.