Optical second harmonic imaging as a diagnostic tool for monitoring epitaxial oxide thin-film growth

Optical second harmonic generation is proposed as a tool for non-invasive, non-destructive, real-time, in-situ imaging of oxide epitaxial film growth. The films can be monitored by surface imaging with a lateral resolution of ≤1 μm on an area of size up to 1 cm2. We demonstrate the potential of the proposed technique by an ex-situ analysis of thin epitaxial SrTiO3 films grown on (1 1 0) NdGaO3 single crystals. Our data show that second harmonic generation provides complementary information to established in-situ monitoring techniques such as reflection high-energy electron diffraction. We demonstrate that this technique can reveal otherwise elusive in-plane inhomogeneities of electrostatic, chemical or structural nature. The presence of such inhomogeneities is independently confirmed by scanning probe microscopy.