Enhancing materials properties via targeted doping

Abstract

In this thesis a series of theoretical studies aimed at enhancing the optical and electrical properties of selected oxide and hydride materials via defect incorporation is presented. Large-scale screening for useful defects was performed on two transparent tin-based oxide materials: a natively p-type tin monoxide and an intrinsically n-type tin dioxide. Novel dopant candidates that promise amplified charge-carrier generation if incorporated successfully were uncovered for both compounds. We further showed that some of these dopant elements are able to maintain the optical properties displayed by the bulk phases of the oxides. The two studies revealed the affinity of tin monoxide for both hole and electron free-carriers when doped appropriately, while tin dioxide was shown to be a strictly n-type conductor. The possibility of improving both optical and electronic attributes of tin-oxide materials further was investigated by exploring the interactions between impurity atoms and intrinsic defects of the host. Isovalent silicon doping in tin dioxide was shown to suppress absorption states arising from oxygen deficiencies, thus, presenting a novel path for improving optical properties in transparent conductive oxide materials. In tin monoxide, halogen interstitials were observed to bond with native tin vacancies ionizing them to higher charge states, which result in improved p-type carrier generation. Finally, acceptor doping was also considered in large band gap hydride materials under compression. Defects in ice, H$_{2}$O, and polyethylene, H$_{2}$C$_{n}$, were studied by identifying high-pressure phases that display covalent bonding and can, therefore, be successfully doped. The possibility of such doped phases displaying a superconducting transition was addressed and a transition temperature of 60 K in ice-X and a 35 K in a polymeric high-pressure phase of polyethylene was estimated.