Shadow evaporation method for fabrication of sub 10 nm gaps between metal electrodes

Ultrasmall gaps are forming in the crossing region of two perpendicular met al strips during the evaporation of the second strip provided the second la yer is thinner than the first layer. This is due to the shadow cast by the first strip during the evaporation of the second. By changing the angle of evaporation of the second strip the size of the gaps can be tuned in the ra nge from 3 nm to 10 nm. Structural characterization of gaps in that range r equires high resolution transmission electron microscopy (TEM). Therefore t hese electrode structures are prepared on ultrathin (thickness 20 nm) elect ron transparent silicon nitride membranes. Ligand stabilized gold clusters (core size 1.5 nm) are attached to these electrode structures using a merca pto-polymer. TEM characterization of the cluster array in the ultrasmall ga p allows to relate the number and position of the clusters in the gap regio n to future transport measurements.