Nanogap Device Engineering for Electrical Characterisation of Molecular Components

Abstract

For the development of molecular electronics, it is essential to measure the electrical characteristics of individual molecular components without altering their structures. This work concerns engineering closely packed identical nanogap devices, that are capable of electrical characterisation of sub-10 nm molecular components. The fabrication process involves growing a GaAs-AlAs-GaAs wafer by molecular beam epitaxy, where the thickness of the AlAs middle layer determines the primary nanogap width. Mesas separated by trenches are patterned on the wafer by reactive ion-beam etching to a depth below the AlAs layer. Some of the AlAs layer is selectively etched, resulting in identical shallow cleavages on the mesa walls. Nanogap devices are constructed by evaporating a network of thin and narrow NiCr/ Au wires crossing the etched mesa cleavages. This step also controls the final nanogap width. The fabricated nanogap devices are used for electrical characterisation of 7 nm wide CdSe nanocrystals, and negative differential resistance behaviour is observed.