Precise microstructuring of indium-tin oxide thin films on glass by selective femtosecond laser ablation

Transparent conductive oxide (TCO) thin films were removed from glass substrates using femtosecond laser pulses. Irradiating through the glass, the threshold for complete TCO ablation was much lower than for front-side irradiation. Additionally, the former method created almost rectangular cross-sectional groove profiles despite the Gaussian laser beam. This indicates a non-thermal ultrafast ablation mechanism via critical carrier concentration achieved by the femtosecond pulse in the TCO at the interface. Very narrow scribes of only 5 µm width provided very good electrical separation, making this technique very attractive for micro-structuring applications like scribing of thin-film solar cells.