Y, Ba, Cu, and Ti interface reactions with SrTiO3 (100) surfaces

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Abstract
Interface reactions of adatoms of Y, Ba, Cu, and Ti with ordered and disordered SrTiO3 (100) surfaces were examined with x‐ray photoemission spectroscopy, Auger spectroscopy, and low‐energy electron diffraction. Atomic distributions for these interfaces before and after annealing at 500 °C were determined using Ar ion sputter depth profiling. We observed strong reactions of Y and Ba with O extracted from the substrate for both ordered and disordered SrTiO3, with the strongest interactions occurring for Y on the disordered surface. These reactions were diffusion limited at 300 K, and the growth of a metal overlayer was observed with increasing coverage. Comparison of these results to those for Ti/SrTiO3 made it possible to determine the extent of the reactions and the reaction products. At elevated temperatures, more extended out‐diffusion of O from the substrate into the overlayer was observed, completing the conversion to the respective metal oxides. In contrast, Cu deposited on SrTiO3 formed clusters on the surface and did not react with the substrate. O out‐diffusion was not observed for the Cu overlayer at elevated temperatures, but clustering was enhanced. The implications of these results are discussed in terms of Y‐Ba‐Cu‐O superconductor synthesis on SrTiO3.