Mechanism of selective removal of transparent conductive oxide layers: Femtosecond-vs. picosecond-laser pulse ablation

Abstract

High average power, high repetition rate ultrashort pulse (τ < 10 ps) laser systems with µJ pulse energies [1, 2] are increasingly used for bio-medical and material processing applications. Interesting applications for the ultrashort pulse laser systems are in the field of selective structuring of thin-films. Thin-film solar cells have shown a big potential to decrease cost of manufacturing for photovoltaic generation. Despite many research attempts to optimize materials the mass production of thin-film solar cells is still looking for versatile tools for the structuring of the thin-film coated area, where thin films with a thickness of ca. 1 µm have to be line-structured with galvanic separation without damaging the substrate or any other layers.In this paper we report on recent results on study of the selective structuring of thin Boron (B) doped ZnO film with femtosecond (fs) and picosecond (ps) laser pulses at 1040 and 1064 nm, respectively. Experimental data on the removal threshold energies for direct and induced (lift off) ablation of thin ZnO film as a function of pulse width and number of laser pulses per position will be presented. The experiments provide additional information about mechanism of direct and induced ablations in femtosecond and picosecond regimes. From comparison of the removal thresholds for both methods we can conclude that the induced ablation is more suitable for the structuring of the TCO layer. On the other hand, structuring of the TCO layers by induced ablation is more complicated due to its strong dependence on the quality of the glass substrate.High average power, high repetition rate ultrashort pulse (τ < 10 ps) laser systems with µJ pulse energies [1, 2] are increasingly used for bio-medical and material processing applications. Interesting applications for the ultrashort pulse laser systems are in the field of selective structuring of thin-films. Thin-film solar cells have shown a big potential to decrease cost of manufacturing for photovoltaic generation. Despite many research attempts to optimize materials the mass production of thin-film solar cells is still looking for versatile tools for the structuring of the thin-film coated area, where thin films with a thickness of ca. 1 µm have to be line-structured with galvanic separation without damaging the substrate or any other layers.In this paper we report on recent results on study of the selective structuring of thin Boron (B) doped ZnO film with femtosecond (fs) and picosecond (ps) laser pulses at 1040 and 1064 nm, respectively. Experimental data on the removal threshold energies for dire...