Fabrication and Electrical Characterization of Correlated Oxide Field Effect Switching Devices for High Speed Electronics

摘要

Metal insulator transitions (MITs) in oxides are an intriguing problem from both a fundamental materialsphysics and an applied technology perspective. Though the precise roles of electron correlations andlattice distortions on the phase transition remains an active area of research, many recent theoreticalstudies have suggested intimate interplay among the orbital splitting/polarization, correlation effects, andPeierls dimerization in the 3d~1 system. Occupied states have been probed by x ray photoelectron spectroscopy(XPS), and a rough structure of unoccupied 3d-like states have been deduced by O K-edge x-rayabsorption measurements. NbO_2, a 4d~1 system, like VO_2 cry stallizes in a distorted rutile type structurewith Nb dimers and undergoes a temperature induced MIT, albeit at a considerably higher temperature of∼1083 K. It is commonly accepted that because 4d orbital valence states are more dispersed in both spaceand energy, Mott physics is less important in 4d transition metal oxides than in 3d ones. Along this line ofreasoning, it is perhaps surprising that the insulating state of NbO_2 persists to higher temperatures thanthat of VO_2.