Transparent conducting oxides and their applications

Realization of next generation photovoltaic and spintronic devices requires the use of materials beyond conventional semiconductors. Metal oxide semiconductors are technologically important for use in next generation devices that require: transparency, multifunctionality and stability. In this work metal oxide semiconductors ZnO and CuBO2 were pursued as transparent conductors and diluted magnetic semiconductors (DMS).;Spintronics has the potential to revolutionize semiconductor device technology; however, in order to realize these devices ferromagnetic semiconductors are required. Three transition metal elements Co, Ni and Cu were selected as potential dopants for ZnO based DMS. Cobalt and Cu doped ZnO were found to be ferromagnetic above room temperature. In Ni doped ZnO ferromagnetic hysteresis was found to correspond to the existence of Ni metal clusters and was found not to be an intrinsic property of the material. Ga co-doped DMS were produced to study the role of charge carriers on the electrical, optical and magnetic properties. In Zn0.95Cu0.05O Ga doping was found to quench ferromagnetism due to charge transfer from Ga to Cu. Ga doping had a quite different effect on Zn0.95Co0.05O, where it was found to increase disorder causing charge carrier localization enhancing the magnetic properties of Zn 0.95Co0.05O. Here it was found that strongly localized carriers with large localization radii can efficiently mediate ferromagnetism at high temperatures.;Transparent conducting oxides (TCOs) are an integral part of modern optoelectronics. Impurity doped ZnO and CuBO2 were explored as n-type and p-type TCOs. Group-IIIb (Al, Ga) doped ZnO thin films were studied with the aim of understanding degenerate doping in these systems. Metal-like conductivity was achieved in highly transparent Zn0.99Ga0.01O and Zn1--xAlxO (x = 0--0.1). It was found that at high dopant concentration (> 4 at.%) disorder in the system caused the optical and electrical properties to degrade. For the application of p-type transparent conductors CuBO2 was synthesized and characterized. The synthesis of CuBO2 was made possible through the use of low temperature bulk and thin film processing techniques. CuBO2 was found to have a high hole mobility (100 cm2/V-s), electrical conductivity (1.65 S/cm) and was identified as having an indirect band gap of 2.2 eV.