Bending Deformation-Induced Drastic Change of the Resistance of Graphene Nano-Ribbons

In this study, first principle calculation based on density functional theory was applied to graphene nanoribbons (GNRs), which is divided to three groups for the number of carbon dimers, with local large bending deformation so as to reveal the effects of the bending deformation on the electronical properties of GNRs for realizing a GNR-base pressure sensor with high sensitivity and large deformability on a flexible substrate. The mechanism of the change in the band gap is discussed in terms of the change in spatial distributions of state densities. It is clarified that bending deformation causes localization of density state and induces the drastic change of band gap in all groups. Based on the calculation results, it is estimated that GNRs can be applied to a pressure sensor and sensitivity is enhanced by increasing the localization of bending deformation. The analyzed result was validated by experiments using a pressure sensor which consisted of GNRs with periodically aligned fine columnar structures. It was confirmed that under the application of compressive stress to the columnar structures caused local large bending deformation of graphene nanoribbons and thus, caused large change of electrical resistance of the deformed graphene ribbons. By increasing the number of columnar in series on a GNR to amplify the local deformation, the sensitivity of the sensor to pressure increased linearly with the number.