Fabrication of nanostructure on Au nano-film by nanosecond laser coupled with cantilevered scanning near-field optical microscopy probe

Abstract

Diffraction limit has been the constraint of the nanostructure fabrication. Because the scanning near-field optical microscopy (SNOM) can work in the evanescent near-field region, its application in nano-processing has received extensive attention from researchers globally. In this paper, we combined nanosecond laser with cantilevered scanning near-field optical microscopy probe. Utilizing the high precision of the confinement and enhancement effect of probe tip and the high instantaneous energy of the laser, we realized nanostructure fabrication and in situ detection on Au nano-film. Feature sizes down to 47 nm full width at half maximum (FWHM) were fabricated. We investigated the laser propagation through the SNOM tip aperture and the light field intensity distribution on the surface of substrate theoretically. The calculation results demonstrate that the laser is highly restricted within the SNOM aperture and enhanced on the exit plane at the rim of aperture. After the transmission, the light field intensity distribution on the surface of the Au nano-film was enhanced due to the localized surface plasmon resonance (LSPR). The thermal distribution on the surface of Au nano-film indicates that the peak of the temperature distribution appeared at the surface right underneath the center of the aperture. It is proved that the simulation results are consistent with the experimental results.