Epitaxial single-crystal thin films of MnxTi1 - xO2 - δ grown on (rutile)TiO2 substrates with pulsed laser deposition: Experiment and theory

SURFACE SCIENCE

卷:632

Article

Ilton, Eugene S.¹  Droubay, Timothy C.¹  Chaka, Anne M.¹  Kovarik, Libor¹  Varga, Tamas¹  Arey, Bruce W.¹  Kerisit, Sebastien N.¹ 

[1] Pacific NW Natl Lab, Richland, WA 99352 USA

关键词: Thin films;    Pulsed laser deposition;    Ab initio thermodynamics;    Rutile;    Manganese;   

DOI  :  10.1016/j.susc.2014.10.013

来源: Elsevier

【 摘 要 】

Epitaxial rutile-structured single-crystal MnxTi1 - xO2 (- delta) films were synthesized on rutile- (110) and -(001) substrates using pulsed laser deposition. The films were characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and aberration-corrected transmission electron microscopy (ACTEM). Under the present conditions, 400 degrees C and PO2 = 20 mTorr, single crystal epitaxial thin films were grown for x = 0.13, where x is the nominal average mole fraction of Mn. In fact, arbitrarily thick films could be grown with near invariant Mn/Ti concentration profiles from the substrate/film interface to the film surface. In contrast, at x = 0.25, Mn became enriched towards the surface and a secondary nano-scale phase formed which appeared to maintain the basic rutile structure but with enhanced z-contrast in the tunnels, or interstitial sites. Ab initio thermodynamic calculations provided quantitative estimates for the destabilizing effect of expanding the beta-MnO2 lattice parameters to those of TiO2-rutile, the stabilizing effect of diluting Mn with increasing Ti concentration, and competing reaction pathways for surface oxide formation. (C) 2014 Elsevier B.V. All rights reserved.

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