Highlights

Light-weight, flexible electronics that can be folded for storage but expanded when needed are attractive for a wide variety of applications, ranging from sophisticated large-area steerable antenna systems for space and aviation systems, to routine consumer electronics applications. Silicon nanomembranes are an ideal candidate for applications that require operation at microwave frequencies. Such membranes can be viewed as a flexible, single crystal. We have developed a simple and robust technique to integrate a single-crystal silicon nanomembrane with a low-cost, low-temperature plastic substrate. More importantly, we have developed the key processes for pre-doping the Si-nanomembrane before transfer to the plastic substrate, thereby realizing a high-quality gate dielectric material at room temperature. These breakthroughs have permitted fabrication of high-performance active thin-film transistors on low-cost, low-temperature plastic substrates. We currently hold the world-record for speed in flexible thin-film transistors, with a maximum oscillation frequency of 7.8 GHz on fairly long channel length devices. This demonstration suggests that monolithically integrated, flexible microwave frequency electronic systems will soon come of age.