February 1, 2015
Journal Article

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

Abstract

Epitaxial rutile-structured single-crystal MnxTi1-xO2-d 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, 400oC 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 tetrahedral interstitial sites. Ab initio thermodynamic calculations provided quantitative estimates for the destabilizing effect of expanding the ß-MnO2 lattice parameters to those of TiO2-rutile, the stabilizing effect of diluting Mn with increasing Ti concentration, and competing reaction pathways.

Revised: February 25, 2020 | Published: February 1, 2015

Citation

Ilton E.S., T.C. Droubay, A.M. Chaka, L. Kovarik, T. Varga, B.W. Arey, and S.N. Kerisit. 2015. Epitaxial single-crystal thin films of MnxTi1-xO2-d grown on (rutile)TiO2 substrates with pulsed laser deposition: Experiment and theory. Surface Science 632. PNNL-SA-102453. doi:10.1016/j.susc.2014.10.013