Two-dimensional materials-based radio frequency wireless communication and sensing systems for Internet-of-things applications

Radio frequency (RF) electronics involving two-dimensional (2D) material-based devices and integrated circuits have been widely advocated as a promising platform for future generations of wireless communication and sensing systems. Monolayer and few-layer 2D materials display exceptional electrical, mechanical, and thermal properties, which can be leveraged for building superior key elements in transceiver/receiver RF front ends, including but not limited to amplifiers, mixers, switches, oscillators, and modulators that enable various forms of signal modulations. In particular, some 2D materials with high intrinsic mobilities can be used as channels of RF transistors that possess high gain, high cutoff frequency (up to hundreds of gigahertz), and excellent abilities in improving the performance of complex analog and RF circuits. Moreover, the (bio-)chemical sensing capabilities of 2D material-based devices may be integrated into RF circuits and modular building blocks for making monolithically integrated wireless nanosensors. The robust, flexible, scalable, and small-footprint features of these 2D devices further allow for development of flexible electronics (e.g., wearable devices, smart skins, and contact lens sensors) that facilitate the practice of ubiquitous sensors and Internet-of-things (IoT). In this chapter, we will review recent advances in RF and microwave transistors based on 2D materials such as graphene and beyond, as well as their potential applications as constituent parts of the IoT hardware.