  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.
