Measurement of electron transport properties of molecular junctions fabricated by electrochemical and mechanical methods

We describe two methods to fabricate metal-molecule-metal junctions. The first method starts with a pair of electrodes separated with a molecular scale gap on an oxidized silicon substrate. These electrodes are fabricated by combining electron beam lithography and electrochemical deposition/etching. A molecular junction is formed when a molecule bridges the gap. This method can fabricate rather stable molecular junctions, however, the yield is low and the exact number of molecules in the junctions is uncertain. The second method forms a molecular junction by separating a scanning tunneling microscope tip from contact with a metal substrate in a solution containing sample molecules. This method, although is not device compatible, can create a large number of molecular junctions over a short period of time, which is ideal for statistical analysis.