Laser sintering and patterning of gallium-doped zinc oxide/indium-tin oxide nanoparticle films with tailorable electrical and optical properties

Gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO) nanoparticles (NPs) were combined to create bi-component suspensions for the drop-casting and CO2-laser sintering of transparent conducting oxide (TCO) thin films with significantly reduced ITO content. An aqueous dispersion of ITO NPs enabled the suspension of GZO NPs without surfactants. Transmission electron microscopy indicated the formation of high aspect-ratio segments of ITO NPs from the suspension through oriented attachment, that persisted in the deposited and sintered thin films to establish an efficient electrical percolating network within the less conductive GZO NP matrix. Rapid CO2-laser sintering under argon gas of approximately 800 nm thick NP films yielded resistivities of 7.34 × 10−3 Ω·cm and 116 Ω·cm for pure ITO and pure GZO respectively. However, a bi-component film with only 19.6 at.% indium (relative to zinc) achieved a resistivity of 3.21 × 10−1 Ω·cm. By changing the ITO content, the near-infrared transmittance could be adjusted between 13% and 82% and the optical bandgap energy between 3.93 and 3.33 eV, enabling fine-tuning of the properties. Finally, a fast and material/energy efficient processing route was demonstrated for the fabrication of a GZO-ITO circuit pattern using CO2-laser patterning of a mask and CO2-laser sintering of the NP films.