Improvement in Photosensitivity of Dumbbell-Shaped Graphene Nanoribbon Structures by Using Asymmetric Metallization Technique

Abstract

Abstract The existence of Schottky barrier between the semiconductive graphene nanoribbon (GNR) and the metallic electrodes at its both ends causes a major hurdle in the development of GNR based devices. Here, a dumbbell-shape GNR structure was proposed to solve the problem. This structure consisted of a semiconductive GNR and wide metallic GNR at both ends. The ohmic contact between the wide metallic GNR and metallic electrode was easily achieved. Furthermore, an effective mechanism to enhance electronic band properties of the dumbbell-shape GNR structure by using asymmetric metallization technique is employed. To achieve this, two different metallic electrodes were introduced, Platinum (Pt) and Titanium (Ti), at each end of the GNR channel to break the symmetry in the Schottky barrier at both ends. The asymmetric difference in the Schottky barrier at the electrode/GNR interface at each ends allows for an efficient directional flow of electrons, effectively separating the photo-generated carriers. The individual contributions at each electrode/GNR interface were summed up resulting in a larger absolute photo-induced current. The electron transfer characteristics of the DS-GNR-FET was studied under an irradiation of a light source with a wavelength of 632.8-nm at room temperature. The developed 70-nm DSGNR-FET showed a significantly larger and enhanced photosensitivity of about 1.6 × 107 A/W.m2 as compared to the device fabricated with identical metallic electrodes as the source and drain electrodes.