Strain and photovoltaic sensitivities of dumbbell-shape GnR-base sensors

The area-arrayed dumbbell-shape Graphene Nano-Ribbons (GNRs) were fabricated by using chemical vapor deposition and photolithography technologies. The electronic behavior of the fabricated GNR-FET structure was evaluated for its photonic properties with an incident light intensity of 1-mW. The 200-nm wide GNRs structure showed metallic properties, while those with the width of 40 nm showed semiconductive properties as was expected. The light-induced photocurrent was observed in all the fabricated GNRs structures. The average photocurrent observed in the 2-mm wide graphene structure was 3.3 A/m² and that observed in the 40-nm wide area-arrayed GNRs structure was 261 A/m², respectively. Based on this photocurrent, the external photosensitivity of the 40-nm wide GNRs structure was about 2.6 x 10⁵ A/W.m² and this value was much larger than that of conventional Si-base solar cells. In addition, the effect of strain on the resistivity of GNRs was measured. Uniaxial tensile strain was applied to the area-arrayed GNRs structures with the width from 200 nm to 40 nm. The gauge factor obtained from the GNRs with the width wider than 100 nm was about 3, and that with the width of 40 nm was about 160. Therefore, highly-sensitive strain sensors can be realized by using GNRs thinner than 70 nm.