Abstract
Growing additional TiO2 thin films on TiO2 substrates in ultrahigh vacuum (UHV)-compatible chambers have many applications for sample preparation, such as smoothing surface morphologies, templating, and covering impurities. However, there has been little study into how to control the morphology of TiO2 films deposited onto TiO2 substrates, especially using atomic layer deposition (ALD) precursors. Here, the authors show the growth of a TiO2 film on a rutile TiO2(110) surface using titanium tetraisopropoxide (TTIP) and water as the precursors at pressures well below those used in common ALD reactors. X-ray absorption spectroscopy suggests that the relatively low sample temperature (175 °C) results in an anatase film despite the rutile template of the substrate. Using ambient pressure x-ray photoelectron spectroscopy, the adsorption of TTIP was found to be self-limiting, even at room temperature. No molecular water was found to adsorb on the surface. The deposited thickness suggests that an alternate chemical vapor deposition growth mechanism may be dominating the growth process. This study highlights the possibility that metal oxide film deposition from molecular precursors is an option for sample preparations in common UHV-compatible chambers.
Highlights
Thin film deposition of TiO2 is routinely performed using methods such as atomic layer deposition (ALD), chemical vapor deposition (CVD), and pulsed laser deposition (PLD)
Depositing TiO2 at 175 C using alternating TTIP and H2O dosing with pressures at and below 1 Â 10À5 Torr resulted in a film that appears to be anatase from the Ti L-edge X-ray adsorption spectroscopy (XAS) data
The XAS suggest a film thickness of at least 10 nm, which is unrealistic for ten ideal ALD cycles; the large thickness suggests that a CVD mechanism could play a dominate role in the deposition
Summary
Thin film deposition of TiO2 is routinely performed using methods such as atomic layer deposition (ALD), chemical vapor deposition (CVD), and pulsed laser deposition (PLD). Ways to control the morphology, impurity concentration, and crystalline phase using ALD are fairly well-known; previous studies have shown that epitaxial growth of TiO2 films is possible using ALD, CVD, and other deposition techniques on substrates with similar lattices, such as Al2O3 (0001), SrTiO3,5–8 LaAlO3,9 RuO2,10 and SnO2 nanowires.. Investigations of the adsorption of ALD precursors on surfaces are commonplace, but there are few studies of CVD processes and cyclic processes of ALD in UHV-compatible chambers.25–28 Feasibility of such deposition could offer a new option to grow materials in UHV-compatible chambers, including a way to obtain a smooth or impurity-free surface, especially when fairly low temperatures during the deposition are required. The apparent thickness of the film is much larger than would be expected for standard ALD ligand exchange mechanisms and could be consistent with a CVD growth mechanism seen by Johnson and Stair in a similar study of TiO2 deposition on MoOx.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
