Steve Kirby "Combinatorial search for transparent conducting oxides"
Transparent conducting and semiconducting materials are quickly becoming more important in many technologies. Among these technologies, flat panel screens and solar cells are two very important technologies that are driving the need for better and cheaper transparent conductors. Currently, tin doped indium oxide (ITO) is the most common transparent conductor used in these applications. There is a desire to limit the amount of indium in future technologies due to the high expense of obtaining large quantities of indium. Our research uses a combinatorial approach of searching for transparent conductors that are either better than ITO in some way or cheaper. We can use the combinatorial approach to quickly examine the effect of doping on known transparent conductors (In2O3, ZnO, CdO, SnO2) or by searching a large area of phase space to find new transparent conducting materials.
Using cosputtered off-axis sputtering, we can deposit a film that has a large range of compositions across the substrate. These films can then be quickly characterized through high throughput optical measurements and four point probe. The optical measurements utilize an Ocean Optics spectrometer and x-y stage. These measurements allow for measurement of reflectivity and transmission of the films. From this we can also measure band gap, plasma frequency and film thickness. The four point probe gives us a quick method to find resistivity. Hall Effect measurements using the van der Pauw technique give further information on the electrical properties. X-ray diffraction and EPMA Microprobe in CCMR are utilized to obtain lattice information and verifying composition.