Effects of precursor concentration on the optical and electrical properties of Sn_XS_Ythin films prepared by plasma-enhanced chemical vapour deposition

Abstract

We have carried out the electrical and optical characterization of thin films of compounds based on Sn-S bonds (SnS 2 , Sn 2 S 3 ), prepared by plasma-enhanced chemical vapour deposition (PECVD), as a function of the relative concentration of the precursor vapours, SnCl 4 and H 2 S, keeping all other deposition parameters constant. In all studied cases, the deposited films were formed by polycrystalline materials. The optical bandgap values of deposited materials were calculated from optical transmittance and reflectance measurements. The SnS 2 compound produced under certain deposition conditions has a forbidden bandgap around 2.2 eV. This compound shows n-type electrical conductivity, whose dark value at room temperature is 2 ×10 −2 ( cm) −1 . Also, it shows the typical semiconductor dependence of its electrical conductivity on the temperature with an activation energy of about 0.15 eV. However, thin films of a mixture of SnS 2 and Sn 2 S 3 compounds were deposited with higher values of the relative concentration of source vapours than those used to obtain the SnS 2 compound. The optical bandgap shows a decreasing trend as the relative concentration increases. A similar trend is observed for dark electrical conductivity. These results create the opportunity to use Sn X S Y compounds in thin films for building heterojunction solar cells prepared completely by PECVD.

Laser-induced SnS2-SnS phase transition and surface modification in SnS2 thin films

“…8(a), the direct and indirect band gaps of the non-irradiated SnS 2 sample were found to be 2.70 eV and 2.62 eV, respectively. The value of the direct band gap is in good correlation with results of theoretical calculations reported in [4], but it is higher than values of about 2.2-2.5 eV obtained in [23,[45][46][47] for SnS 2 thin films. The relatively broad band gap of the SnS 2 sample could be due to the quantum size effect, since the FESEM and AFM studies show that the thickness of platelet-like grains at the surface is less than 100 nm.…”

Assessment of the potential of tin sulphide thin films prepared by sulphurization of metallic precursors as cell absorbers

“…Note that these values for both indirect and direct transitions refer to SnS phases, [4,7]. No influence of SnS 2 phases were detected, which present an energy band gap above 2.0 eV [13]. This result is due to the fact that in a solid mixture the optical behaviour of the material is ruled by the one with lower band gap energy.…”

Structural and optical studies of chemically deposited Sn2S3 thin films

“…Among these, Sn x S y is very promising as a material for the researchers, due to its different phases and properties [5]. Most of the studies working on Sn x S y thin films have fabricated SnS, SnS 2 thin films by using different deposition methods [6][7][8][9][10][11][12]. Nevertheless, it should be noted that until now, little research has been undertaken on the deposition of Sn 2 S 3 thin films.…”