Analyzing UV/Vis/NIR Spectra-Sputtered ZnO:Al Thin-Films—I: Space-Time Depend

Exact, contact-free and non-destructive optical analysis of semiconducting layers is 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/visible (Vis)/near infra-red (NIR) spectra. Special focus has been set on single-layer systems. Approximations for thin-films upon substrates and measurements without integrating sphere are provided. Complex parameter evaluation is provided. This exact data acquisition model provides deeper insight into the process-parameter dependencies of pulsed direct current sputtered, transparent aluminum doped zinc-oxide (ZnO:Al) thin films, upon glass substrates. ZnO:Al thin films have been analyzed 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, d_TarSub, and sputter durations, t_Sp . 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. Theoretical sputter-concepts were proved and enhanced. A non-contact, optical conductivity measurement possibility by use of UV/Vis/NIR spectroscopy has been provided. Optically evaluated conductivities, σ_L, were compared with electrically taken values, by a four-tip measurement system.