Band gap of epitaxial in-plane-dimerized single-phase NbO₂films

Abstract

Structure, band gap, and Mn-related mid-gap states in epitaxial single crystal (Zn1−xMgx)1−yMnyO thin films

Final-state effect on x-ray photoelectron spectrum of nominallyd1andn-dopedd0transition-metal oxides

“…LaTiO 3 is already metallic at room temperature, which easily allows for charge fluctuation. For NbO 2 , the sample is still nominally insulating at room temperature, but its relatively small band gap of ∼1.0 eV [23] likely results in non-negligible concentration of electrons in the conduction band at room temperature. The fact that no sample charging is observed during XPS measurements indicates that there is sufficient conductivity in the samples at room temperature (sufficient thermally excited carriers in the conduction band) to allow for charge fluctuation to occur.…”

“…All films reported here are crystalline as-deposited, with pseudo-rutile structure for NbO 2 [23] and perovskite structure for SrVO 3 and LaTiO 3 , as determined by reflection high energy electron diffraction (RHEED). We systematically vary the oxygen pressure during growth to determine the conditions that would result in the ideal O:Nb, O:Ti, and O:V ratios in the films.…”

“…Undoped SrTiO 3 is nominally d 0 , while the remaining three materials are nominally d 1 : in the ionic limit, SrTiO 3 has no electron occupying the Ti 3d orbital; NbO 2 has one electron occupying the Nb 4d orbital; SrVO 3 and LaTiO 3 have one electron occupying the V 3d and Ti 3d orbital, respectively. NbO 2 films are grown on 111-oriented SrTiO 3 substrates as described in more detail elsewhere [23]. Both SrVO 3 and LaTiO 3 films are grown on 100-oriented SrTiO 3 substrates at a temperature of 600-800…”

Preparation, characterization, and electrical properties of epitaxial NbO2thin film lateral devices

“…Previous reports have focused on a broad range of film qualities, ranging from amorphous [2][3][4] to epitaxial quality [8,9]. Films grown on Al 2 O 3 (0001) substrates using magnetron reactive sputtering resulted in NbO 2 (110) and (111) crystal orientations [8], while films grown on (La,Sr) 2 (Al,Ta) 2 O 6 (111) substrates using molecular beam epitaxy had both (100) and (320) out-of-plane orientations [9].…”

“…Recently there has been a growing interest in materials demonstrating metal-insulator transitions (MITs) because of their possible applications in electronic devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Among these materials is NbO 2 which exhibits one of the highest MIT temperatures of 1081K [16][17], accompanied by a structural transition from a distorted rutile (low temperature) to a rutile structure (high temperature phase).…”