Laser-induced forward transfer of intact, solid-phase inorganic materials

Abstract

Laser-induced forward transfer (LIFT) is a technique for the micro- and nanofabrication of photonic, electronic and biomedical devices. Compared to conventional methods of device microfabrication, LIFT offers the unique features of transfer of functional and sensitive thin films with a minimum of material damage in an intact state and a user-defined shape. The objective of this thesis is the definition of conditions and the demonstration of applications for LIFT-printing of inorganic solid thin films using spatially-shaped laser pulses to reduce the need of additional sacrificial layers, lithographic or annealing process steps.

The LIFT-printing of piezoelectric and thermoelectric materials onto planar target substrates (receivers) was studied and their dynamics, transfer velocity and the existence of shock waves was examined via time-resolved shadowgraphy. The deposit-receiver impact phase was modelled via finite-element analysis and was compared to experimental results of the nanosecond-LIFT of thermoelectric chalcogenide films. The printing onto elastomer-coated substrates improved the transfer quality, the adhesion between deposit and receiver, and enabled single pad sizes of 15mm2 leading to the fabrication of a working energy harvesting device exclusively via LIFT. Advancements to the LIFT technique were presented, enabling the transfer of intact single-crystalline donors and conductive lines from molten copper micro-droplets. Shaping of the spatial laser pulse profile via digital micromirror arrays and homogenising optics increased the efficiency and the direct-write capability of the laser-machining setup for LIFT and ablation.

The results of this thesis contributed to expand the range of applicable thin films, led to the identification of regimes for the LIFT of brittle inorganic solid thin films in an intact state, and introduced improvements to the laser-machining setup for rapid-prototyping and device manufacturing without the need of additional post processing steps.

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Identifiers

ORCID for Robert W. Eason: orcid.org/0000-0001-9704-2204

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