Growth of β-MnO2 films on TiO2(110) by oxygen plasma assisted molecular beam epitaxy

We have used oxygen plasma assisted MBE to grow epitaxial films of pyrolusite (beta-MnO2) on TiO2(110) for thicknesses of one to six bilayers (BL). We define a bilayer to be a layer of Mn and lattice O and an adjacent layer of bridging O within the rutile structure. The resulting surfaces have been characterized in situ by reflection high-energy electron diffraction, low-energy electron diffraction, X-ray photoelectron spectroscopy and diffraction, and atomic force microscopy. Well-ordered, pseudomorphic overlayers form for substrate temperatures between 400 and 500 degrees C. Mn-Ti intermixing occurs over the lime scale of film growth (similar to 1 BL/min) for substrate temperatures in excess of 500 degrees C. Films grown at 400-500 degrees C exhibit island growth, whereas intermixed films grown at temperatures of 500-600 degrees C are more laminar. 1 BL films grown at 450 degrees C are more laminar than multilayer films grown at the same temperature, and form a well-ordered surface cation layer of Mn on the rutile structure with at most 10% indiffusion to the second cation layer. (C) 1999 Elsevier Science B.V. All rights reserved.