Optical emission spectroscopy in pulsed laser deposition of silicon

The generation of a homogeneous plasma plume is necessary for the pulsed laser deposition of thin films. In this work, we investigate the effects of nanosecond-duration laser pulses to ablate polycrystalline Si targets in vacuum (<10−4 Pa) at room temperature. The laser wavelength covers the range from ultra-violet to infrared by using a KrF (248 nm, 25 ns) and a Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) laser. The films were deposited at laser fluences from 1 to 6 J/cm2 and characterized by atomic force microscopy and spectroscopic ellipsometry. Time-integrated optical emission spectra were obtained for excited neutrals and ionized Si species in the plasma produced between 0.5 and 11 J/cm2. The relation between the ionized species and film properties were discussed.