AVS 57th International Symposium & Exhibition
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuA

Paper EM-TuA9
Control of Oxygen Diffusion in Titanium Dioxide for Nanoelectronic Applications

Tuesday, October 19, 2010, 4:40 pm, Room Dona Ana

Session: Defects in Semiconductors and Oxides
Presenter: E.G. Seebauer, University of Illinois at Urbana-Champaign
Authors: A. Hollister, University of Illinois at Urbana-Champaign
P. Gorai, University of Illinois at Urbana-Champaign
E.G. Seebauer, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
The technologically useful properties of semiconductor oxides such as titania often depend on the concentration and motion of defects. Native point defects such as interstitial atoms and vacancies strongly affect the operation of nanoelectronic gas sensors, light emitting diodes and memory resistors. Past work in our laboratory with silicon has shown that semiconductor surfaces serve as efficient pathways for generation and annihilation of point defects in the underlying bulk. Such pathways should play an especially important role in nanoelectronics fabrication, where devices have high surface-to-volume ratios. The present work extends the findings for silicon to the oxide semiconductor TiO2, wherein we have identified a new pathway for interstitial-mediated diffusion of oxygen in titanium oxide. Oxygen diffusion rates were measured by exposing natural-abundance single-crystal rutile TiO2 to isotopically labeled oxygen gas. The resulting profiles were measured by secondary ion mass spectrometry and subsequently modeled with continuum equations for the reaction and diffusion of the key point defects that control oxygen diffusion. The exponential diffusion profile shapes, together with the increase of the diffusion coefficients with oxygen pressure, strongly suggest the diffusion is mediated by oxygen interstitials. The measured diffusion coefficients were nearly two orders of magnitude higher than those expected from the literature, but could be decreased substantially by the adsorption of submonolayer quantities of sulfur to saturate surface dangling bonds. These latter observations suggest that the pristine TiO2 surface is especially efficient at creating oxygen interstitials that then sink into the bulk and mediate diffusion there.