Part2: Ultra-short pulse laser patterning of very thin indium tin oxide on glass substrates

TL;DR

This study explores laser patterning of ultra-thin ITO films on glass using femtosecond and picosecond pulses at various wavelengths, revealing a primarily non-thermal ablation mechanism confirmed by surface analysis and temperature simulations.

Contribution

It provides detailed fluence thresholds and mechanisms for ITO removal with ultrafast lasers, advancing understanding of non-thermal ablation processes in thin film patterning.

Findings

Ablative removal occurs at specific fluence thresholds across wavelengths.

Surface analysis confirms fluence-dependent selective removal.

Simulations show non-thermal mechanisms dominate below 1 J/cm2.

Abstract

We investigate selective patterning of ultra-thin 20 nm Indium Tin Oxide (ITO) thin films on glass substrates, using 343, 515, and 1030 nm femtosecond (fs), and 1030 nm picoseconds (ps) laser pulses. An ablative removal mechanism is observed for all wavelengths at both femtosecond and picoseconds time-scales. The absorbed threshold fluence values were determined to be 12.5 mJ/cm2 at 343 nm, 9.68 mJ/cm2 at 515 nm, and 7.50 mJ/cm2 at 1030 nm for femtosecond and 9.14 mJ/cm2 at 1030 nm for picosecond laser exposure. Surface analysis of ablated craters using atomic force microscopy confirms that the selective removal of the film from the glass substrate is dependent on the applied fluence. Film removal is shown to be primarily through ultrafast lattice deformation generated by an electron blast force. The laser absorption and heating process was simulated using a two temperature model (TTM). The predicted surface temperatures confirm that film removal below 1 J/cm2 to be predominately by a non-thermal mechanism.