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Termination control of NdGaO3 crystal surfaces by selective chemical etching

A chemical etching method was developed for (110) and (001) NdGaO3 single crystal substrates in order to obtain an atomically flat GaO2-x - terminated surface. Depending on the surface step density the substrates were etched in pH-controlled NH4F- or NH4Cl-based solutions, followed by an annealing step at temperatures of 800-1000oC, in air or in oxygen flow, in order to recrystallize the surface. Atomic Force Microscopy (AFM) and high-pressure Reflection High Energy Electron Diffraction (RHEED) were used to analyse the surface morphology of the samples after every treatment. Studies on the chemistry and characteristics of the terminating layer showed that the chemically etched NdGaO3 substrate surface has a GaO2-x termination and that the (110) and (001) NdGaO3 surfaces are characterized by a different free surface energy, which is lower for latter.