Quench rate enhancement in pulsed laser melting of Si by processing under water

The thermal quench rate during pulsed laser heating of Si can be enhanced by immersing the sample in a liquid (e.g., water) during irradiation. The liquid in contact with the irradiated surface acts as an additional heat sink increasing the thermal quench rate. The heat transfer processes and phase transformations were studied in real time using transient optical reflectance and electrical conductance techniques. Measurements of the melting and solidification dynamics of the Si reveal that the quench rate may be enhanced by 30% for deep melts. The measurements also indicate that a steam or superheated water phase is formed near the Si surface during the laser pulse. The observed phenomena are analyzed in terms of standard heat flow.