Effectof annealing temperature on opticaland electrical propertiesof SnS thin films


SnS thin films have been depositedat R.T. with thickness (300 nm ± 0.01) by using a thermal evaporation technique and annealed at 200°C for 2hour.The optical band gap of the SnS film determined from optical transmittancespectrum, in the range (400-1100 nm)and the data was used to calculate absorption coefficient and optical band gap. The film as grownand annealed has shown a direct band gap ~ 2.24 eV and 2.17eV respectively.The optical constant such as extinction coefficient (k), absorption coefficient (α) and refractive index (n) have been evaluated.At the annealing temperature the SnS film had the best electrical properties the mobility was up to 52.35 cm².V¯¹.s ¯¹, and the resistivity was about 0.14×106(Ω.cm).Keywords: Tinsulfied, thinfilms, Thermal evaporation, Optical & electrical properties.1. Introduction In recent years, thin films of SnS have attracted much for photovoltaic applications due to the high absorption (>104cm-¹)[1,2] and high conductivity .SnS belongs to groups IV-VI compounds formed with Sn as the action and Sas the anion .The constituent elements are inexpensive, nontoxic and abundant in nature leading to the development of devices that are environmentally safe and have public acceptability.SnS is animportant optoelectronic material that is found in zinc blend with lattice constant (a=0.5845 nm ) [3], orthorhombic with lattice constants (a=0.385 nm, b= 1.142 nm c= 0.438 nm ) [4,6] crystal structures.The optical properties of SnS vary depending on synthesizing or fabrication method, but most work agrees with direct (1.2-1.5 eV ) and indirect (1.0-1.2eV) band gap values. These properties enable SnS thin films to be used as an absorption layer in the fabrication of hetrojunction solar cell [7].