Structural, Electronic and Magnetic Properties of GaMnN, MnN and Rare-Earth Nitride Thin Films

Abstract

Materials that combine the useful properties of magnetic and semiconducting behaviours are sought for new and developing applications in electronics. In this thesis experimental studies of the properties of disordered thin films of several potentially magnetic semiconducting materials are presented. Previous research on the diluted magnetic semiconductor GaMnN is reviewed as an introduction to a study of GaMnN thin films grown with an ion-assisted deposition technique. Several complementary compositional and structural analysis techniques are used to determine that films can be grown with as much as 18 at. % Mn content and that contain no impurity phases, as are often detected in single crystalline GaMnN preparations with high Mn concentrations. The effects of varying Mn contents on the resistive, optical and magnetic properties of the thin films are investigated. The structural, electronic and magnetic properties of thin films of the potential impurity phase MnN have also been investigated and compared with band structure calculations. Recent predictions that the rare earth nitrides may have extremely useful electronic properties have been almost untested in the literature. A procedure for growing rare earth nitride thin films and capping them to protect from reaction with water vapour allows their resistivity, structural and magnetic properties to be established. The results on GdN, SmN, ErN and DyN support the recent predictions, and a more thorough study on GdN reveals that this material is a ferromagnetic semiconductor below 69 K.