Self-Sustaining Tunable Multi-Frequency Oscillators Using Atomically-Thin Semiconducting Multimode Resonators

Case Western Reserve University, Cleveland OH

Investigators

Abstract

Mechanical oscillators are essential and ubiquitous in many critical applications from fundamental science explorations to communication and sensing technologies. While miniaturization of devices in recent decades has created many resonant micro- and nanoelectromechanical systems (MEMS and NEMS) as new frequency references for making oscillators and clocks, major challenges remain in engineering ultralow-power, low-noise crystal oscillators by utilizing emerging resonators in new nanostructures. This project aims to discover new science and engineering principles in multi-frequency self-sustained oscillators enabled by multimode resonators based on atomic layer two-dimensional (2D) semiconductors, with a focus on previously unexplored effects and potentially unprecedented functions and performance. 2D NEMS are based on mechanically active atomically-thin semiconducting crystals derived from "beyond-graphene" layered materials that offer a spectrum of attractive electromechanical attributes. Multimode 2D NEMS resonators are a new class of vibrating NEMS with intriguing and tunable properties rich in their multiple resonance modes. With frequency reference and selectivity functions harnessed from multimode 2D NEMS resonators vibrating in radio-frequency (RF) and microwave bands, the self-sustaining feedback oscillators are distinct from passive resonators in that they possess their own stable limit cycles, and can sustain periodic oscillations without an external periodic drive. The goal of the integrated STEM educational plan is to educate and motivate youth by (i) a new outreach program for K-12 students to understand oscillations and learn the fascinating history of clocks and timing devices, (ii) summer research at Case Western Reserve University (CWRU) for high-school students, and (iii) actively broadening participations from underrepresented and economically disadvantaged groups, especially by extending outreach programs to public schools in Cleveland area. The objectives of this project are to demonstrate that 2D semiconductors can enable highly tunable self-sustaining oscillators, to develop the principles of 2D NEMS oscillator engineering and on-chip integration, and to explore pathways toward ultimate limits of crystal oscillators in the 2D platform. This project will establish the fundamental principles of signal transduction and feedback mechanisms in 2D crystal oscillators, lay the foundation for ultralow-power and tuning circuit design suitable for 2D systems, and address critical challenges in small-signal detection, parasitic effect suppression, nonlinearity, tuning and power handling. It will also explore phase noise in self-sustaining oscillations in 2D crystals at RF and microwave frequencies. The research will be enabled by innovative feedback circuit designs that will go significantly beyond the simple sustaining amplifiers that are sufficient for single-resonator, single-mode feedback oscillators. This project features a circuit-device co-design perspective, with the goal of eventually enabling entirely new, monolithic, multimode oscillators with phase noise engineering. This project will create and establish a new branch, 2D crystal oscillators, in the rapidly emerging and growing field of 2D devices and systems. The research will generate a plethora of new knowledge in both device physics and engineering principles that govern the 2D crystal oscillators, thus broadening the horizon of current knowledge of 2D systems. The findings shall also lead to enabling technologies for 2D timing and frequency control functions in atomic layers. This will contribute to establishing 2D electromechanical systems as a new pillar, in parallel to electronics and optoelectronics based on atomic layers, to support the future 2D semiconductor paradigm.