Near-Infrared Femtosecond Laser for Studying the Strain in $\hbox{Si}_{1\hbox{-}{\rm x}}\hbox{Ge}_{\rm x}$ Alloy Films via Second-Harmonic Generation

The second-harmonic generation (SHG) from Si1-xGex alloy films has been investigated by near-infrared femtosecond laser. Recognized by s-out polarized SHG intensity versus rotational angle of sample, the crystal symmetry of the fully strained Si0.83Ge0.17 alloy is found changed from the Oh to the C2 point group due to the inhomogeneity of the strain. Calibrated by double crystal X-ray diffraction,...