Role of polytypism and degree of hexagonality on the photoinduced optical second harmonic generation in SiC nanocrystalline films

• Strong influence of polytypism in SiC NC on the output SHG was found.
• Increasing hexagonality favors enhanced SHG.
• SHG efficiency is inversely proportional to delying time between fundamental and SHG maxima.

Photoinduced optiсal second harmonic generation was studied in nanocrystalline SiC films prepared by the method of direct ion deposition. For the studies were chosen three types of polytypes (with different degree of hexagonality) – 24R with degree hexagonality G=25, 27R-G=44, 33R with – G=36. The bicolor photoinduced treatment was performed by the wavelengths 1064nm/532 nm by 15 ns YAG:Nd laser. The efficiency of the output SHG was evaluated by ratio of the corresponding signal intensities with respect to the references and by the time delay between the SHG and the fundamental maxima. Explanation of the observed effect is given within a framework of the occurrence of the nano-trapping levels in the film crystalline interfaces.