Microdroplet deposition of copper film by femtosecond laser-induced forward transfer

Copper microdroplets were deposited onto a quartz substrate by the laser-induced forward transfer (LIFT) using laser pulses of 148fs at a center wavelength of 775nm. The droplets with 2–3μm diameters were transferred at a laser pulse energy slightly above the threshold at which the copper film could be removed completely. The droplet formation was a result of the blow-off of a molten film from the quartz substrate by a compressive stress of plasma when the free surface was melted and was different from the microdroplet formation by the LIFT technique using nanosecond laser pulse.