Flexible radio frequency interconnect of reduced graphene oxide

Abstract

Flexible interconnects are attracting significant attention owing to their key role in flexible electronic devices as well as their tendency to carry high frequency to all areas of electronics. The radio frequency (RF) characteristics of reduced graphene oxide (rGO) were measured to determine its transmission properties in various bending states. The results obtained for the original flat state were compared with those obtained for a progressively bent state and for a post-measurement, flat recovery state. Both the bent and flat states exhibited a small difference in real and imaginary impedance. De-embedding was performed to exclude the background signal from the substrate and electrodes without using the rGO. In the case of high-frequency transmission and reflection signals, the difference between the bent and flat states was noteworthy; however, there was a small difference in impedance. The impedance gradually increased with the degree of bending of the rGO film up to a small difference from the flat state. It then returned to its initial level when the film returned to its flat state (i.e. the recovery state). The cause of these impedance changes was analyzed by studying the wrinkles, adhesion, strain, and defects of rGO using scanning electron microscopy, atomic force microscopy, x-ray diffraction, and Raman spectroscopy. The impedance increased with bending due to defects between the flakes. However, the degree of increase in impedance was compensated for by the presence of wrinkles and the reduction in the interlayer distance. This approach is readily adaptable for use in flexible RF interconnects.