The dynamics of the explosion of a liquid film by an ultraviolet excimer pulsed laser is studied experimentally on top of an amorphous silicon (aSi) film deposited on fused quartz. In particular, the transient temperature as well as the nucleation of the superheated liquid at the interface for laser fluences below and above the spontaneous nucleation threshold are monitored using an optical transmission technique. Results for different pure and mixed liquids are presented for cases of different thicknesses of the a-Si film. Details for the calibration of the transmission signal to obtain the interface temperature are provided through the application of the one-dimensional diffusion model and the characteristic matrix theory using data obtained from previous steady-state experiments. The calibrated results are in reasonable agreement with the known data for superheated liquids in the literature as well as theoretical calculations. In addition, the delay times for spontaneous nucleation of the liquids are estimated to be 5 1 ps, generally comparable with those observed in droplet explosion experiments.

Effect of deposition temperature on the optical transmission and paramagnetic centers in pulsed laser deposited amorphous silicon carbide thin films Interplay of latent heat and timedependent nucleation effects following pulsedlaser melting of a thin silicon film

The temperature dependence of the optical constants for amorphous silicon (a-Si) is studied for two different sample thicknesses at two infrared wavelengths. It is observed that the extinction coefficient of a-Si can increase significantly with temperature in the strong absorption regime. In addition, using the Mott-Davis formula, results are obtained for the variation of the optical gap energy for a-Si with temperature, with similar feature observed for both amorphous and crystal silicon.

The transient temperature field development during heating of an amorphous silicon (a-Si) film, deposited on a fused quartz substrate, by pulsed excimer laser irradiation is studied. Static reflectivity and transmissivity measurements are used to obtain the thin film optical properties at elevated temperatures. Experimental in-situ, transient, optical transmission data are compared with heat transfer modeling results. The variation with temperature of the material complex refractive index across the thin film thickness is taken into account. The effects of the film thickness and thermal diffusivity, as well as of the laser pulse shape, are discussed.

The explosion or rapid vaporization of a liquid tllm on an opaque surface by a pulsed laser is studied experimentally. Using a probe-beam deflection sensing (PDS) scheme, together with a previously developed transmission monitor, the distortion of the PDS signal due to the generation of shock waves by the exploding liquid is investigated. Various liquids, including alcohols and pure water in contact with substrates such as polyimide, amorphous carbon, and silicon, are studied for a wide range of excimer laser fluences. It is concluded that the present PDS technique is highly sensitive to the explosion threshold.