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

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.