It has been proposed that a planar silver layer could be used to project a super-resolution image in the near field when illuminated near its plasma frequency [J. B. Pendry, Phys. Rev. Lett. 86, 3966 (2000)]. This has been investigated experimentally using a modified form of conformal-mask photolithography, where dielectric spacers and silver layers are coated onto a tungsten-on-glass mask. We report here on the experimental confirmation that super-resolution imaging can be achieved using a 50-nm thick planar silver layer as a near-field lens at wavelengths around 365 nm. Gratings with periods down to 145 nm have been resolved, which agrees well with our finite-difference time domain (FDTD) simulations.

Patterning at resolution below the diffraction limit for projection optical lithography has been demonstrated using evanescent near-field optical lithography with broadband illumination (365–600 nm). Linewidths of 50 nm and gratings with 140 nm period have been achieved. Ultrathin photoresist layers in conjunction with conformable photomasks are employed and a reactive ion etching process using ${\mathrm{SF}}_{\mathrm{6}}$ has been developed to transfer the patterns to a depth of more than 100 nm into silicon. Full electromagnetic field simulations of the exposure process show that a high contrast image is present within the resist layer, and that the exposure is dominated by one polarization for the grating structures studied.

A single-electron memory cell, in which one bit of information is represented by the excess or shortfall of a precise number of electrons, is described. An experimental memory circuit was fabricated using side-gated constrictions in δ-doped GaAs, and the basic operation was confirmed from 30 mK up to liquid-helium temperature of 4.2 K. This memory can store information for longer than several hours. The intrinsic single-electron memory characteristics in a regime where cotunneling is neglected are investigated, and the overall characteristics are explained by a semiclassical model.