Crystalline orientation effects on conical structure formation in femtosecond laser irradiation of silicon and germanium

Irradiation of Si(100), Si(111), Si(110), Ge(100), and Ge(111) is compared for 150fs, 800nm wavelength pulses in a rough vacuum atmosphere. The surface crystalline orientation of the material is found to affect the final morphology, with (111)- and (110)-surface orientations exhibiting a much higher tendency for conical structure formation under multiple-pulse irradiation. Using cross-sectional transmission electron microscopy, the structures …