Intrinsic defect dependent resistivity in semiconducting oxides

Abstract

A multitude of today's electronic devices require a material which is both optically transparent and electrically conductive in order to operate as intended. Several such materials have been developed, and are technologically well understood. However, there are still unanswered questions related to how these materials behave on the nanoscale. While it is well known that defects in the atomic structure are crucial for the electronic properties of these materials, exactly which defects are important and how they interact is generally not known. This thesis explores how the electrical resistivities of a selection of transparent conductive materials change when defects are introduced into their atomic structures via ion irradiation. Compelling evidence is found for three individual effects: At low ion doses, atoms and molecules which have adsorbed to the material surface from exposure to the ambient are removed, recovering the native surface structure. As the dose is increased, individual bulk point defects are formed in sufficient concentrations to affect the resistivity, and at yet higher doses, these defects can combine into defect complexes. Each of these three effects have the potential to significantly change the resistivity, and have been compiled into a general model which is applicable to any semiconductor material.