High Performance Laser Scribing of Advanced Thin Film Materials

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Thin film materials have broad application in electronics, light source, renewable energy, sensors, mechanical systems, etc. With the emergence of new thin film structures there is increasing demand for high performance laser scribing techniques capable of producing narrow ( 10 micron), straight walled cuts with little imparted surface damage. The research aims to address this challenge at the fundamental level by studying the laser-matter interaction mechanisms under a new laser double pulse irradiation strategy for thin film scribing. The basic research from this project will generate scientific knowledge to enable the development of high performance laser scribing techniques that can find application in numerous advanced technology areas including scribing of solar cells and smart window glass, patterning of flexible electronics, micromachining of microelectromechanical systems and light emitting diodes, etc. In the solar industry, for example, recent years have seen tremendous progress in thin film solar photovoltaics, especially perovskite solar cells exceeding 20 percent power conversion efficiency. The research could accelerate the adoption of thin film solar technology and contribute to a clean energy future free of air pollution, hazardous waste, and negative environmental impact. Besides potential industrial and societal benefits, engaging educational materials and activities derived from the project will be developed to train a diverse group of undergraduate and graduate students, and to educate both K-12 students and the public. The principle investigator will take advantage of the new laser micromachining infrastructure to involve students from underrepresented groups in the project. The research will verify that a femtosecond-picosecond double pulse irradiation will create a uniform critical electron number density through multiphoton absorption and avalanche ionization and enable a narrow thin film scribe with high surface integrity. The research objective is to identify the parameter window for pulse energy and time delay, and determine the laser-matter interaction mechanisms under this double pulse irradiation scheme. A combined experimental and numerical modeling approach will be used to verify the approach and to gain a deep understanding of electron dynamics and ablation mechanisms in a thin film structure when irradiated by a femtosecond-picosecond pulse train. The basic technical approach is to develop a numerical model to predict the free carrier density and the resulting ablation shape, while a model-based approach will be used to design and conduct thin film scribing experiments. This research will contribute to the scientific community by advancing the fundamental understanding of laser-matter interaction with advanced thin film materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.