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

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 NiFe/2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT)/NiFe nanojunctions with a junction area of 42 × 42 nm. In this study, toward the realization of a smaller junction area, we fabricate NiFe/C8-BTBT/NiFe nanojunctions using our advanced method. As electrodes in our nanojunctions, 7-nm-thick NiFe 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 NiFe thin film. Using these electrodes, we have successfully fabricated NiFe/C8-BTBT/NiFe nanojunctions with a junction area of 7 × 7 nm, 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.