Laser induced surface and structural modification of germanium in liquid environments

Laser-induced surface and structural modifications of germanium (Ge) in liquid environments of deionized water and ethanol have been investigated. Single crystal Ge (100) has been exposed by KrF excimer laser at four different fluences. Scanning electron microscope analysis reveals the formation of cavities, cracks, and ripples in case of ablation in deionized water, whereas the formation of cavities, ridges, and pores is observed in case of ablation in ethanol. The distinctness, density, and size of cavities are significantly larger in deionized water as compared to ethanol. It is attributed to lower absorption coefficient of deionized water (0.2 × 10−2/mm) as compared to ethanol (1.2 × 10−2/mm) for 248 nm, and consequently, more energy deposition to Ge takes place in the case of ablation in deionized water as compared to ethanol. Fourier transform infrared spectroscopy shows the formation of C-H stretching vibration band in case of ethanol at two moderate fluences. Raman spectroscopy reveals that only Ge-Ge band is formed at 300 cm−1 in both environmental conditions. The electrical conductivity of the irradiated Ge has been increased as compared to unirradiated Ge. However, it was observed that conductivity decreases with increasing laser fluence and also shows a strong dependence on ambient environment.