SELECTIVE FEMTOSECOND LASER STRUCTURING OF A PLATINUM/TANTALUM PENTOXIDE THIN FILM LAYER SYSTEM BY INDUCED LASER ABLATION INVESTIGATED WITH PUMP-PROBE MICROSCOPY

摘要

A biocompatible sensor chip consists of a 200 nmconducting platinum layer between a glass substrateand a 200 nm tantalum pentoxide layer as insulator ontop. The irradiation of the biochip from the Ta_2O_5 sidewith ultra-short laser pulses ( 660 fs) at a wavelengthof 1053 nm leads to a selective ablation of the Ta_2O_5layer from the platinum. The ablation threshold for theremoval of the Ta_2O_5 layer is about 0.08 J/cm~2.Moreover, the Ta_2O_5 lifts-off in form of an intact diskat a fluence of 0.14 J/cm~2. For deeper understanding ofthe ablation mechanisms, a pump-probe microscopysetup was utilized to record a stop-motion movie of thelift-off process. The setup utilizes an opticallycombined with an electronically delayed probe pulse.For the first time to our knowledge the laser lift-off ofa transparent oxide could be recorded over thecomplete temporal dynamic range. The movies revealthat an intact disk leaves the hole after a few 10 ns. Athigher fluences of about 0.20 J/cm~2 the disk disrupts inseveral particles at about 40 ns.