Abstract
Sputter deposition of oxide materials in a high-pressure oxygen atmosphere is a well-known technique to produce thin films of perovskite oxides in particular. Also interfaces can be fabricated, which we demonstrated recently by growing LaAlO3 on SrTiO3 substrates and showing that the interface showed the same high degree of epitaxy and atomic order as is made by pulsed laser deposition. However, the high pressure sputtering of oxides is not trivial and number of parameters are needed to be optimized for epitaxial growth. Here we elaborate on the earlier work to show that only a relatively small parameter window exists with respect to oxygen pressure, growth temperature, radiofrequency power supply and target to substrate distance. In particular the sensitivity to oxygen pressure makes it more difficult to vary the oxygen stoichiometry at the interface, yielding it insulating rather than conducting.
Highlights
INTRODUCTIONHigh pressure sputtering in pure argon using an off-axis geometry,[18] which presumably led to the desired stoichiometry
Ever since the pioneering work by Ohtomo & Hwang[1] in 2004 there has been interest in studying the properties of the interface between band insulators such as LaAlO3 (LAO) and SrTiO3 (STO), which yield conducting interfaces and a two-dimensional electron gas
Interfaces can be fabricated, which we demonstrated recently by growing LaAlO3 on SrTiO3 substrates and showing that the interface showed the same high degree of epitaxy and atomic order as is made by pulsed laser deposition
Summary
High pressure sputtering in pure argon using an off-axis geometry,[18] which presumably led to the desired stoichiometry. We report in more detail on radiofrequency (RF) sputter deposition of LaAlO3 on SrTiO3 in an on-axis geometry and using a high oxygen pressure. We show the outcome of the growth process under different parameters and the effects of post annealing treatments. In particular with respect to temperature and oxygen pressure we find a growth window for depositing smooth and crystalline films, which appears to preclude the correct stoichiometry for obtaining interface conductance. Using a La-poor target did not make a difference, nor did the use of argon as sputter gas instead of oxygen
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