Fabrication of single-crystalline aluminum nanostructures

Single-crystalline Al films were grown on silicon (111) wafers using the method of Miura et al. (1993). The films were patterned into wire structures by electron-beam lithography and dry-etching. For a sub-50 nm line width, the high-resolution part of the pattern was defined in the negative tone of a PMMA film which was used as the image layer in a three-layer resist system. Large structures were defined in outline in the positive tone of the same PMMA film. Magnetoresistance and Little-Parks oscillations were measured in wire arrays of 100 x 1000 square cells with sides of 1 mu m and a line width of approx40 nm. Compared to polycrystalline Al structures the single-crystalline structures have a longer electron phase coherence length and electron mean free path and are very immune to electrical breakdown by electrostatic discharge, etc.