Lift-Off Ablation of Metal Thin Films for Micropatterning Using Ultrashort Laser Pulses

Abstract

Laser ablation of metal thin films draws attention as a fast means of clean micropatterning. In this study, we attempt to remove only the metal thin film layer selectively without leaving thermal damage on the underneath substrate. Specifically, our single-pulse ablation experiment followed by two-temperature analysis explains that selective ablation can be achieved for gold (Au) films of 50–100 nm thickness by the lift-off process induced as a result of vaporization of the titanium (Ti) interlayer with a strong electron–phonon coupling. With increasing the film thickness comparable to the mean free path of electrons (100 nm), the pulse duration has to be taken shorter than 10 ps, as high-temperature electrons generated by the ultrashort pulses transfer heat to the Ti interlayer. We verify the lift-off ablation by implementing millimeters-scale micropatterning of optoelectronic devices without degradation of optical properties.