Time-Resolved Studies of Surface Melting During Laser-Induced Chemical Vapor Deposition with Laser Intensity Modulation

ABSTRACTThermal laser-induced chemical vapor deposition of gold deposits has been studied using a modulated Ar+ laser. Deposition of gold from dimethylgold hexafluoroacetylacetonate is accompanied by surface melting of the deposit when laser source is modulated. Time-resolved reflectance measurements have been used to study the surface reflectance during growth with modulated and unmodulated laser source. The reflectance measurements indicated that surface melting does not occur under unmodulated cw irradiation at equivalent laser intensities. Variation in the modulation duty cycle indicates that there is a minimum laser-off cycle time length required for surface melting to be observed. Evidence is presented which suggests that surface melting is due to the heat released by the exothermic decomposition of reactant adsorbed during the time that the laser intensity is off.