Analyzing UV/Vis/NIR Spectra-Sputtered ZnO:Al Thin-Films III: Plasma-Parameter Dep.

Exact, contact-free, and nondestructive optoelectrical analysis of transparent conductive oxide layers have been discussed within this tripartite publication, in view of solar cell production. In part I and part II, two different nonnumerical theoretical models, the single-layer model and the double-layer model, were introduced. They made an extraction of approximation-free optical and electrical data from ultraviolet/visible/near-infrared spectra possible. Here, interpolation methods have been discussed, in order to compute efficiently correct and continuous streams of (complex) data. These exact data acquisition models provide deeper insights into the process-parameter dependencies of sputtered aluminum-doped zinc-oxide (ZnO:Al) thin-films upon glass substrates. Therefore, ZnO:Al thin-films were analyzed with respect to geometrical and time-dependent conditions during the sputter process in part I and with respect to gas-law dependencies in part II. Here, the influence of plasma-parameters on the physical values of the sputtered ZnO:Al thin-films has been investigated. Thence, variations of the frequency, f , (the break time, tBr) and the power, P, of the plasma-building electromagnetic fields were analyzed and discussed. 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 noncontact, 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.