The effect of deposition rate and heat treatment on conduction and charge carrier transport mechanisms in Sb2S3 films

Thin nonstoichiometric Sb2S3 films were prepared by thermal evaporation technique, with different deposition rates. The films whether as deposited or after being annealed were noncrystalline i.e., they have amorphous nature. The structure investigations of Sb2S3 bulk form showed that it has orthorhombic phase with lattice parameters: a=1.12, b=1.13 and c=0.384 nm. Energy dispersive X-ray analysis showed that the samples prepared with the deposition rate 0.5 and 6 nm s−1 are rich in Sb whilst those prepared with the deposition rate 2.5 nm s−1 are rich in S. Dark electrical resistivity and space charge limited conduction for nonstoichiometric films of different thicknesses prepared with three different deposition rates (0.5, 2.5 and 6 nm s−1) were measured before and after annealing. The nonstoichiometric Sb2S3 films showed semiconducting behavior with the existence of two distinct thermal activation energies ΔE1 and ΔE2 belonging to two impurity levels, deep level ΔE1 and shallow level ΔE2. The deep level was also detected by space charge limited current technique. The trap density Nt was determined. The electrical properties of Sb2S3 had been discussed on the bases of the nonstoichiometry of the samples under investigation.