2ND-HARMONIC GENERATION AS A PROBE OF ANTIPHASE DOMAINS IN LAYERED GASE THIN-FILMS ON SI(111) SUBSTRATES

Second harmonic generation (SHG) at 1.064 μm reflected by thin films (20-60 nm) of layered GaSe epitaxially grown on Si(111) substrates is reported. Comparison with a theoretical calculation, taking into account all interfering waves, is made as a function of growth temperature, evidencing a large discrepancy at lower growth temperature. This discrepancy is attributed to the existence of antiphase domains whose nonlinear polarizations are opposite. Reflected SHG thus allows to probe the existence of an orientational disorder undetectable with electron or x-ray diffraction techniques.© 1995 American Institute of Physics.