Material ejection dynamics in direct-writing of low resistivity tracks by laser-induced reverse transfer

Laser-induced reverse transfer (LIRT) is a direct-write technique for patterning materials onto transparent substrates. A laser pulse transmits through the transparent material and a small air gap to ablate a donor target surface, the vaporised target species then transfers to the transparent material. There is not yet a detailed understanding of the material ejection and deposition processes, and reports show high-resistivity films and only limited demonstration of conductive linear tracks. Here we use a recently developed capability of holographic phase contrast imaging at nanosecond temporal resolution to report the morphology of the confined ablation plume. This reveals previously unobserved phenomena such as the influence of the rebounding pressure wave and an >80% longer plasma lifetime of a confined plume, showing the importance of plume shielding and incubation effects for applications. Focusing on silver, graphite and copper, static and scanned beam experiments show the dominant role of sputtering of fragmented particles rather than vapour condensation. The results highlight the challenges in using LIRT for conformal coating without surface damage but will excite further study of this rarely explored technique, with potential for facile, reliable fabrication of conductive patterns and digitally controlled customisation of glass products for applications such as embedded sensors and electronics.