A conventional sol–gel method is used to prepare metal oxide precursor films and then a 700 nm thick film of silver nanowires is spray coated onto the precursor film. The silver nanowires act as the plasmonic local heat source. Subsequently, a mixed (800 nm + 400 nm) laser beam is directed at the films, exciting the silver nanowires to induce plasmonic local heating which, when combined with ultraviolet-induced photochemical reactions, promotes localized and rapid conversion of metal oxide precursors into high quality metal oxide thin films. The unconverted precursor is removed with oxalic acid and silver residues are wiped off. The high-quality nature of the films is confirmed with X-ray photoelectron spectroscopy, grazing-incidence angle X-ray diffraction and time-of-flight secondary ion mass spectrometry.
A variety of high-quality metal oxide thin films can be produced using the plasmonic printing method including conductors (indium tin oxide (ITO)), dielectrics (AlOx) and semiconductors (indium–gallium–zinc oxide (IGZO), indium–zinc oxide (IZO) and InOx). As different precursors are necessary for different metal oxides, conversion temperatures are different and so laser intensity must be optimized. The plasmonic printing process can also be used to fabricate fully solution-processed metal oxide thin-film transistor arrays.
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