Shadow-evaporated nanometre-sized gaps and their use in electrical studies of nanocrystals

We have developed a technique for fabricating arrays of gaps as small as 3?nm between metal electrodes using a shadow-evaporation technique. These small gaps are fairly reliable and reproducible, and can in principle be made in large quantities, for example across a whole silicon wafer. The gaps can be used to measure the electrical properties of nanoelectronic systems, such as nanocrystals. Our electrical measurements of CdSe nanocrystals 4.2?nm in diameter at 4.2?K show steps in the current?voltage characteristics related to the filling of electronic shells in the nanocrystal and to Coulomb charging.