Laser Microstructured Metal Thin Films as Promising Alternative for Indium Based Transparent Electrodes

In the search of alternative materials for substituting indium tin-oxide, thin films of copper and aluminum (5 to 40 nm) were structured using direct laser interference patterning with nanosecond and picosecond pulse lasers to improve their optical properties. Using this method, periodic patterns consisting on micro-scaled holes were produced. It was found that the optical transmittance of the structured layers could be increased between 25 to 125% while the electrical resistance was marginally influenced. In addition, improvements in the diffuse transmittance are demonstrated for the processed materials. The laser treatment could enhance the diffuse to total transmission ratio (HAZE) by values ranging from 30 to 82%. The results also show that both of the studied metals succeed to match the frame of properties that is set by typical applications requiring indium thin oxide (ITO) films. For both ns- and ps-based structuring processes, numerical simulations are performed to investigate the ablation mechanisms of the thin films.