Nanogap Device Engineering for Electrical Characterisation of Molecular Components

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 nanogap devices that are suitable for electrical characterisation of sub-10 nm molecular components. The fabrication process involves embedding a thin layer of AlAs between two thick layers of Gads layers by molecular beam epitaxy that controls the primary nanogap width. Mesas separated by trenches are patterned by reactive ion-beam etching. The mesa sidewallsform the active regions, -where some of the AlAs layer is selectively etched by hydrofluoric acid, resulting in identical shadow cleavages. Nanogap devices are constructed by thermally evaporating thin layers of NiCr/Au crossing the etched mesa cleavages. The nanogap devices are used for electrical characterisation of 7 nm wide CdSe nanocrystals, and negative differential resistance behaviour is observed.