Effects of Laser Wavelength and Fluence in Pulsed Laser Deposition of Ge Films

Abstract

Nanosecond lasers with ultra‐violet, visible and infrared wavelengths: KrF (248 nm, 25 ns) and Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) were used to ablate polycrystalline Ge target and deposit Ge films in vacuum (<10‐6 Torr). Time‐integrated optical emission spectra were obtained for laser fluence from 0.5–10 J/cm2. Neutrals and ionized Ge species in the plasma plume were detected by optical emission spectroscopy. Ge neutrals dominated the plasma plume at low laser fluence while Ge+ ions above some threshold fluence. The deposited amorphous thin‐film samples consisted of particulates of size from nano to micron. The relation of the film properties and plume species at different laser fluence and wavelengths were discussed.