Fig. 4

Spatial resolution of NSOM scanning. A single horizontal nanoslit (slit width of 60 nm, 120 nm, or 180 nm) was formed in a Cr film (65-nm thick): see top panels for SEM images. The NSOM scan profiles at y = 0.16 µm (red), 0.31 µm (green), and 0.47 µm (blue) at 633 nm wavelength: see bottom panels. a 60-nm slit sample showing 92 nm FWHM. b 120-nm slit sample showing 120 nm FWHM. c 180-nm slit sample showing 178 nm FWHM