Abstract
Pairs of electrodes with nanometer separation (nanogap) are achieved through an electromigration-induced break-junction (EIBJ) technique at room temperature. Lithographically defined gold (An) wires are formed by e-beam evaporation over oxide-coated silicon substrates silanized with (3-Mercaptopropyl)trimethoxysilane (MPTMS) and then subjected to, electromigration at room temperature to create a nanometer scale gap between the two newly formed An electrodes. The MPTMS is an efficient adhesive monolayer between SiO2 and An. Although the An wires are initially 2 pm wide, gaps with length similar to 1 nm and width similar to 5 nm are observed after breaking and imaging through a field effect scanning electron microscope. This technique eliminates the presence of any residual metal interlink in the adhesion layer (chromium or titanium for An deposition over SiO2) after breaking the gold wire, and it is much easier to implement than the commonly used low-temperature EIBJ technique which needs to be executed at 4.2 K. Metal-molecule-metal structures with symmetrical metal-molecule contacts at both ends of the molecule are fabricated by forming a self-assembled monolayer of -dithiol molecules between the EIBJ-created An electrodes with nanometer separation. Electrical conduction through single molecules of 1,4-Benzenedimethanethiol (XYL) is tested using the Au/XYL/Au structure with chemisorbed gold-sulfur coupling at both contacts.
Date of this Version
May 2006