Characterization of femtosecond-laser-ablated a germanium single crystal in air by using X-ray diffraction

Ablation of germanium single crystals in air is performed with femtosecond laser pulses (150 fs, 1 kHz) of 800-mn wavelength in the fluence range of 0.52similar to26 J/cm (2). Two different semi-logarithmic relationships between the ablation depth and the laser fluence are observed. The structure of the ablated region is characterized by means of XRD, including a wide angle (theta/2theta) scan and the rocking curve of (400) plane. The ablated layer exhibits several polycrystalline diffraction patterns and double peaks in the rocking curve, which are related to structural defects. From these investigations, the higher laser fluence in the second semi-logarithmic region obviously causes severe damage to the structure of the ablated zone.