Near-field optical scanning microscopy with tunnel-distance regulation
by U. Durig, D. Pohl, F. Rohner
Unprecedented optical image resolution (20 nm to 30 nm) has been obtained with a near-field optical scanner using light with a wavelength of half a micrometer. The key element is an extremely small aperture (~10 nm) placed at the very top of a pyramidal screen. The aperture is scanned in the immediate proximity of the surface to be investigated, using vacuum tunneling to sense the distance. The amount of light transmitted by both the aperture and the sample depends sensitively on the optical properties of the sample in the immediate vicinity of the aperture.