Parallel fabrication of monolithic nanoscopic tunnel junctions for molecular devices

Abstract

Nanoelectrode tunneling devices for molecular level measurements have been grown using atomic layer deposition. These devices are two-terminal nanostructures separated by a free space region on the order of one to several nanometers where molecules can adsorb and be probed with electrical measurements including electron tunneling spectroscopy. Successful fabrication of parallel devices arranged in arrays is achieved by exploiting a nanofeedback mechanism that aids in the convergence of independent devices to tunneling. Independent devices are shown to behave similarly for thermal expansion, adsorption, desorption, and tunneling spectroscopy measurements. Adsorption is shown to be strongly influenced by the large electric fields in the nanoscopic tunnel junctions, and a model based on electric field forces qualitatively captures these effects. Desorption events are observed as stochastic processes for the independent devices and parallel inelastic electron tunneling spectroscopy measurements show features that are similar between independent devices. These data demonstrate parallel operation of nanoelectrode devices and suggest that it may be possible to scale the devices to have many nanojunctions operating in parallel.