Effects of thin-film thermal conductivity on the optical damage threshold of a-Si film on c-Si substrate at 1064 nm

Optical damage tests have been performed on a pair of a-Si film on c-Si substrate samples to determine their respective damage-threshold values. The thermal properties of the two samples have been determined previously in a noncontact, nondamage fashion [B. S. W. Kuo, J. C. M. Li, and A. W. Schmid, Appl. Phys. A 55, 289 (1992)], thus providing opportunity to relate the damage threshold to the thermal properties while controlling other factors. The samples have similar film thermal conductivity but much different interface thermal resistance. The damage test results show that the one with higher interface resistance is more vulnerable to high laser-pulse energy. A heat-transfer model involving both film thermal conductivity and interface thermal resistance has been developed to predict the damage-threshold dependence on film thickness. The result using predetermined thermal properties agrees with experimental data qualitatively. It also indicates that the interface property is the dominant factor here, while the impurity-dominant model cannot be applied, since no difference would be predicted for the two samples.