Nanosecond laser-induced thermal evaporation of silicon carbide

Excimer (XeCl) laser pulses, 15 ns in duration and with fluences up to 10 J · cm^–2, have been employed to induce melting and evaporation of 6H-SiC thin layers in vacuum. Sample surface modification in the nanosecond time scale have been tnonitorizedin situ by optical probing. Eventually, the ablation product was collected on silicon single-crystal substrates placed in front of the SiC target. Modeling of the heating and the thermal evaporation processes resulted in estimation of surface temperatures as high as 10,000 K, evaporation rates of the order of 10²⁵ molecules · cm^–2 · s^–1 and recoil pressures of the order of 1 GPa. Comparison with experiments showed that the simple mechanism of purely thermal evaporation is able to describe the process of particle removal from a surface by short laser pulses only in the low-energy density range. Above a certain threshold the model breaks down and other mechanisms have to be considered.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29, 1995, Köln, Germany.