Selective ablation of thin films with short and ultrashort laser pulses

• DOI: 10.1016/j.apsusc.2005.06.057
• Publication Date: 2005-11-03T08:37:29Z
• Authors: J. Hermann; M. Benfarah; G. Coustillier; S. Bruneau; E. Axente; J.-F. Guillemoles; M. Sentis; P. Alloncle; T. Itina
• Keywords: [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics]; 02 engineering and technology; 0210 nano-technology; 7. Clean energy

Abstract Micromachining of CuInSe 2 (CIS)-based photovoltaic devices with short and ultrashort laser pulses has been investigated. Therefore, ablation thresholds and ablation rates of ZnO, Mo and CuInSe 2 thin films have been measured for irradiation with nanosecond laser pulses of ultraviolet and visible light and subpicosecond laser pulses of a Ti:sapphire laser. The experimental results were compared to the theoretical evaluation of the samples heat regime. In addition, the cells photo-electrical properties were measured before and after laser machining. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses were employed to characterise the laser-induced ablation channels. Using nanosecond laser pulses, two phenomena were found to limit the laser-machining process. Residues of Mo that were projected onto the walls of the ablation channel and the metallization of the CuInSe 2 semiconductor close to the channel lead to a shunt. The latter causes the decrease of the photovoltaic efficiency. As a consequence of these limiting effects, only subpicosecond laser pulses allowed the selective or complete ablation of the thin layers without a relevant change of the photo-electrical properties.