Femtosecond laser-triggered electrical discharges at nanoprobe tips for nanoprocessing

Electrical discharges were stimulated by femtosecond laser pulses in nanoscale gaps between sharpened metal tips and gold film. Laser pulses with intensity 5.6 1011 W/cm² reliably triggered discharges in sub-micron and microscale gaps. For gaps shorter than a threshold value, the discharge stimulation probability was near unity, over a range of applied potentials. At a lower laser intensity of 3.5 × 10¹¹ W/cm² the discharge stimulation probability characteristics were similar to those at higher intensity, but only for the higher applied potentials (60 80V) used. At lower applied potential, the discharge probability was also lower and depended on potential. With current limiting diode, the discharge current reached a peak value in about 2ns, and extinguished after an additional 2 3ns. Scanning Electron Microscopy studies show that micron-sized gold surface region were melted and re-solidified by the electrical discharge.