Fig. 1. (a) Experimental system for direct writing of LIPSS in ITO films by a femtosecond laser. (b) Schematics of laser polarization, focal spot, scanning direction, transverse and longitudinal directions. HWP: half-wave plate, CCD: charge-coupled device.

Fig. 2. SEM images of ITO films irradiated by lasers with different fluences. (a) 0.212 J/cm², (b) 0.446 J/cm², (c) 0.531 J/cm², and (d) 0.679 J/cm². The inset shows an enlarged view of the area indicated by the red square. The scanning speed was 3 mm/s. The scanning direction and the direction of the electric field E are shown in (a).

Fig. 3. Laser fluences and scanning speeds for the three types of surface morphologies.

Fig. 4. (a) SEM image of a large-area regular LSFL. (b) Enlarged image of the red square in (a). (c) Fourier transform image of (b). (d) Cross-sectional profile of the confocal optical micrograph of (b).

Fig. 5. Sheet resistance of ITO film after laser direct writing with different fluences at a constant scanning speed of 3 mm/s.

Fig. 6. Ratio of the sheet resistance along the transverse (T) and longitudinal (L) directions with respect to the laser fluence at a constant scanning speed of 3 mm/s.

Fig. 7. Resistivities of nanowires fabricated using lasers with different fluences.

Fig. 8. (a) SEM images of nanowires fabricated via laser direct writing with different fluences. (b) Height and width of nanowires with respect to the laser fluence. (c) Unit resistance and resistivity of nanowires with respect to the laser fluence.

Fig. 9. Transmission spectra of the ITO film after laser direct writing with different fluences at a constant scanning speed of 3 mm/s.

Fig. 10. (a–c) Distributions of In and Sn for the ITO film with the LSFL; the scale bar represents 1 μm. Map sum spectra for the (d) ridge and (e) valley of the LSFL.

Fig. 11. Concentrations of In and Sn and the In/Sn ratio at the (a) ridge and (b) valley of the LSFL with respect to the laser fluence.

Fig. 12. (a) Distributions of In and Sn and (b) resistivity and sheet resistance for ITO films with different thicknesses.