Pulsed current annealing of sputtered amorphous ITO films

The complicated structure of electronic devices makes the conventional annealing method, which involves placing the entire device in a furnace, insufficient for achieving the desired quality. This issue is currently addressed through the use of pulsed laser annealing, where a specific target layer is heated, preventing the overheating of other layers or the substrate. However, this method is only applicable to a very limited range of materials and requires very expensive, powerful pulsed laser sources. Herein, a novel approach for the selective local thermal treatment of thin films is proposed; in this method, short, powerful current pulses are applied to the target conductive layer. The application of two current pulses with a length of 1.5 s induced the crystallization of a 160-nm thick indium tin oxide (ITO) film, resulting in a sheet resistance of 8.68 Ω·sq⁻¹, an average visible light transmittance of 86.69%, and a figure of merit (FoM) of 293.61. This FoM is an order of magnitude higher than that of the as-prepared ITO film, and to the best of our knowledge, is among the highest reported values for the polycrystalline ITO films. Simulations have shown that even faster and more localized crystallization could be achieved by increasing the power of pulsed current. This novel annealing method is applicable to most semi-conductive or metallic thin films and requires only a relatively inexpensive pulsed current source, making it potentially more attractive than pulsed laser annealing.

Graphical Abstract