Thin Solid Films, Vol.519, No.19, 6568-6578, 2011
Analysing UV/Vis/NIR spectra with the double-layer model - Sputtered SnS thin-films II: Gas law and plasma parameter dependencies
Exact, contact-free and non-destructive optical analysis methods are advantageous for controlled thin-film deposition processes, especially for optical detector and solar cell applications. Within this second part, of a bipartite publication, a non-numerical theoretical model - the double-layer model has een presented to extract approximation-free optical and electrical data from ultra-violet/visible/near infra-red spectra. So, analysis of double-layer systems, as thin-films upon substrates, was possible. Complex parameter evaluation is possible. This exact data acquisition model provides insights in the process-parameter dependencies of radio frequency sputtered, opaque tin-sulphide thin-films upon glass substrates. They have been analysed on the one hand with respect to the equation of state for real gases (gas law). Therefore, the argon pressure within the process-chamber and the substrate-temperature were varied. On the other hand, tin-sulphide layers have been properly analysed and discussed with respect to plasma-parameter dependencies. Therefore, the frequency, the break time and the power of the plasma-building electromagnetic fields were varied. The systematic influence of these process parameters on a variety of opto-electric physical values of the tin-sulphide thin-films was worked out, carefully. 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 ultra-violet/visible/near infra-red spectroscopy has been provided. Contact-free, optically measured conductivities were compared with those, measured electrically with a conventional four-tip measurement system. (C) 2011 Elsevier B.V. All rights reserved.
Keywords:Optical spectroscopy;UV/Vis/NIR;Optical conductivity;Tin sulphide;Thin films;Sputtering;Real gases equation of state