Titanium-oxygen reaction at the Ti/La1.85Sr0.15CuO4 interface

Abstract
High‐resolution x‐ray photoemission has been used to study the reaction between vapor deposited Ti and La1.85Sr0.15CuO4. For low Ti coverages we observe a sharp decrease in electron emission within ∼2 eV of the Fermi level because of disruption of hybrid Cu 3dx2y2‐O 2px,y orbitals, the loss of metallic character of the surface region, and the loss of superconductivity. Ti 2p and O 1s core level results show that oxygen is removed from the superconductor to form TiO2 at low coverages. At higher coverage, the reaction becomes diffusion limited; a Ti‐rich oxide or solution grows. The Cu 2p3/2 emission shows that oxygen withdrawal rapidly reduces the Cu2+ configuration. Ti metal forms after ∼10 Å deposition.