NANOSTRUCTURE FABRICATION BY ELECTRON-BEAM LITHOGRAPHY ON INSULATING SUBSTRATES USING A NOVEL 4-LAYER RESIST

At low temperatures in the K- and mK-range sapphire substrates are advantageous because of their excellent thermal conductivity. To fabricate nanometer structures by electron beam lithography, problems arise due to the electrical insulating property of Al2O3. To avoid charging effects, which would deteriorate the proper image transfer, a novel four-layer resist system has been developed, allowing the fabrication of well defined metallic nm-structures by lift-off. To demonstrate the application of this technique, lateral point contacts were fabricated, whose I-V characteristics correspond to a phonon spectrum which is typical for ballistic electron transport within the constriction.