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HL: Fachverband Halbleiterphysik

HL 66: Thin Oxides and Oxide Layers II (joint session DS/HL)

HL 66.6: Vortrag

Donnerstag, 19. März 2020, 12:15–12:30, CHE 91

High resistive NbO2 thin-films for phase-change switching applications — •Julian Stoever, Jos E. Boschker, Nazir Jaber, Saud Bin Anooz, Martin Schmidbauer, Jutta Schwarzkopf, Martin Albrecht, and Klaus Irmscher — Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany

Niobium dioxide has recently gained increased interest as it exhibits a semiconductor-metal transition together with a structural phase transition similar to that of vanadium dioxide. (VO2). In contrast to VO2, NbO2 has phase transition temperature of 1080 K, which is well above room temperature and makes the material very interesting for resistive switching devices. We demonstrate the growth of single-crystalline NbO2(001) by pulsed laser deposition on MgF2(001) substrates. A subsequently performed annealing step results in a significantly sharper symmetric NbO2(004) x-ray diffraction peak and in a change of surface morphology. Ellipsometry, absorption spectroscopy and temperature-dependent resistivity measurements (TDR) were performed on the epitaxial layers. A single-crystalline NbO2 bandgap energy of 0.89±0.03 eV was consistently measured. This is in good agreement with density functional theory calculations by O’Hara et al. [J. Appl. Phys. 116, 213705 (2014)]. Furthermore, TDR were performed to determine deep level defects in the material. Finally, we will demonstrate first NbO2 epitaxial layers on sapphire (Al2O3) substrates. Sapphire appeared to be more stable during the annealing, resulting in promising NbO2 epitaxial layers.