Analyzing UV/Vis/NIR Spectra-Sputtered ZnO:Al Thin-Films—II: Gas Law Dependencies

Abstract

Exact, contact-free, and non-destructive optical analysis of transparent conductive oxide (TCO) layers was still done with an extended single layer model (see Analyzing UV/Vis/NIR Spectra-Sputtered ZnO:Al Thin-Films-I: Space-Time Dependencies). Extending this single layer model for use with double layer systems, as TCO thin-films upon substrates, includes an approximation, which is usually negligible. Therefore, a non-numerical theoretical model for analyzing complete double-layer systems (DLM), without any approximations, is provided here. Complex parameter evaluation is possible. For Part I, the influence of geometrical and temporary conditions within the sputter chamber, as target-substrate distance dTarSub, position r upon the substrate and sputter duration tSp, on thin-film parameters were investigated. Here, this exact data acquisition model for double layer systems (DLM) provides by far deeper insight in thin-film parameter dependences from the equation of state for real gases (gas law) during the sputter process. Therefore, ZnO:Al thin-films upon boron silicate glass substrates have been analyzed with respect to the argon pressure, p, within the process-chamber and the substrate-temperature, T. Again, the 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 measured conductivities, σL, were compared with those, measured electrically with a four-tip measurement system.