Micro Patterning of Crystalline Structures on a-ITO Films on Plastic Substrates Using Femtosecond Laser

It is well known that the resistivity and transparency of indium tin oxide (ITO) can be improved by utilizing a thermal annealing process to transform the original amorphous microstructure to a crystalline structure. However, the annealing process may result in irreversible damage to the underlying substrate; particularly if the substrate is fabricated from a plastic material. Accordingly, this study proposes a novel method for the fabrication of crystalline ITO (c-ITO) patterns on plastic substrates using femtosecond lasers with either a low (1 kHz) or a high (80 MHz) repetition rate. The resulting c-ITO patterns are observed using scanning electron microscopy (SEM). The results show that the pattern width varies logarithmically with the laser irradiation energy. In addition, it is shown that a high repetition rate is beneficial in suppressing the formation of micro-cracks on the surface of the c-ITO patterns.