Fabrication of molecular nanoscale junctions with a junction area of 7 × 7 nm² and their structural and electrical...

Molecular electronics has received considerable attention because molecular devices can provide several unique properties, such as giant magnetoresistance, a large Seebeck effect, and nonvolatile switching properties. These unique properties, including enhanced performances, have been observed in molecular nanoscale devices. Therefore, the miniaturization of molecular devices is a key issue for their practical use as well as for the development of fundamental science. In a previous study, we proposed a new nanojunction fabrication method using thin-film edges and successfully fabricated Ni₇₈Fe₂₂/2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT)/Ni₇₈Fe₂₂ nanojunctions with a junction area of 42 × 42 nm². In this study, toward the realization of a smaller junction area, we fabricate Ni₇₈Fe₂₂/C8-BTBT/Ni₇₈Fe₂₂ nanojunctions using our advanced method. As electrodes in our nanojunctions, 7-nm-thick Ni₇₈Fe₂₂ thin films sandwiched between low-softening-point glasses can be fabricated using the thermal pressing technique. The area of the nanojunctions is determined from the thickness of the Ni₇₈Fe₂₂ thin film. Using these electrodes, we have successfully fabricated Ni₇₈Fe₂₂/C8-BTBT/Ni₇₈Fe₂₂ nanojunctions with a junction area of 7 × 7 nm², which is the minimum value ever reported for edge-to-edge nanodevices, and observed electrical conduction through C8-BTBT molecules in the devices. Our study provides a novel nanofabrication technique and opens new opportunities for research in molecular nanoelectronics.