Analyzing UV/Vis/NIR spectra with the single-layer model—Sputtered SnS thin films I: Space–time dependencies

Exact, contact-free and non-destructive, optical analysis of semiconducting layers, are advantageous for thin film solar cell applications. A non-numerical theoretical model has been developed to extract approximation-free optical and electrical data from UV/Vis/NIR spectra. Special focus has been set on single layers; an adequate single-layer model is provided. Complex parameter evaluation is possible.This exact data acquisition model provides deeper insights in the process–parameter dependencies of pulsed direct current and radio frequency sputtered, opaque tin-sulphide thin films upon glass substrates. They have been analysed with respect to space–time dependencies of the sputter process. Therefore, sputter-depositions have been examined, referring to positions upon the substrate, r, target-substrate distances, dTarSub, and sputter durations, tSp. Theoretical sputter-concepts were proved and enhanced. Results were compared with those of the well-known Keradec/Swanepoel model. The necessity of taking both spectra—transmission and reflection spectra—into account has been shown.A non-contact, optical conductivity measurement possibility by use of UV/Vis/NIR spectroscopy has been provided. Optically evaluated conductivities, σL, were compared with electrically taken values, by use of a four-tip measurement system.