Electronic, magnetic and optical properties of oxide surfaces, heterostructures and interfaces: role of defects

Abstract

In this thesis, pulsed laser deposition was utilized for oxide thin films and heterostructures fabrication. Electrical and magnetotransport properties of reduced SrTiO3 (STO) single crystals and STO thin films were investigated, where Fermi liquid exists in STO3-x single crystals while MIT induced by the carrier freeze-out effect emerges in STO3-x films. Atomically flat interfaces between STO films and single-terminated LaAlO3 (LAO) substrates were achieved and determined to be insulating. The origin of the 2DEG at the LAO/STO interface was explored. In addition, reversible room-temperature ferromagnetism was observed in highly-doped (>= 0.5wt%) NSTO single crystals and found to be induced by oxygen vacancies and closely related to carrier density. More importantly, a quasi-conduction band consisting of defect states in LAO was proposed to explain the electric-field-induced reversible MIT in the resistive switching of metal/LAO/NSTO heterostructures. Electronic and magnetic properties of SrRuO3/LaAlO3 (SRO/LAO) superlattices were tuned by varying SRO layer thickness.