Nonlinear Optical Study of Nano‐Sized Effects in a‐Si: H Thin Films Deposited by RF‐Glow Discharge

Abstract

We have evidenced the high sensitivity of infrared‐induced second harmonic generation (IR‐ISHG) to the structural changes occurred in amorphous hydrogenated silicon films (a‐Si: H) prepared by RF‐glow discharge technique at different substrate temperatures and doping types. In every case, a maximal signal of the IR‐induced SHG is achieved at temperature of about 110 K and pump‐probe delaying time about 22–39 ps. It indicates a marked effect of doped subsystems in the observed nonlinear optical effects. A substantial effect of doping is established from a drastic change of the IR‐induced SHG behavior presenting an anomaly at about 400 MW/cm2 for a pumping power with wavelength 1.54 μm. A minimum of the SHG is observed in that case for standard nondoped films. Note here that the doping type does not affect the behavior of the second‐order nonlinear optical susceptibility. The thermo annealing leads to a slight decrease of the effective second‐order susceptibilities. Larger changes are observed with doped samples for the pump‐probe delaying time from about 39 till 24 ps.