A Numerical Study on Nonequilibrium Heat Transfer and Crater Formation in Thin Metal Films Irradiated by Femtosecond Pulse Laser

The ultimate goals of this study are to investigate numerically nonequilibrium energy transfer between electrons and phonons, and to predict the crater formation shapes of gold thin film structures irradiated by femtosecond pulse lasers. In particular, the present article expands the onedimensional two-temperature model (1DTTM) to the two-dimensional model (2DTTM) considering wave interference, and it involves the quantum effect to predict thermal and optical properties. The predictions by using 2DTTM are extensively compared with those of 1DTTM, and the influence of film thickness on radiation heat transfer and optical characteristics are also examined. From the results, it is found that the predictions of 2DTTM are in good agreement with those of 1DTTM. As the gold film thickness decreases, the reflectivity decreases dramatically and the absorbed laser intensities at the top surface increases substantially because of wave interference in thin films.