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Ultra-Wide Bandgap Crystals for Resonant Nanoelectromechanical Systems (NEMS)

Zheng, Xuqian
http://orcid.org/0000-0003-4705-771X
http://rave.ohiolink.edu/etdc/view?acc_num=case1554765522327938

Abstract Details

2019, Doctor of Philosophy, Case Western Reserve University, EECS - Electrical Engineering.
Resonant nanoelectromechanical systems (NEMS) made from two-dimensional (2D) crystals have attracted increasing research interest owing to their promises for exceptionally high responsivities and sensitivities to external stimuli, enabled by their ultralow weight and ultrahigh surface-to-volume ratio. Although 2D crystals with bandgaps ranging from 0 eV to 2 eV have been studied in earlier explorations (such as 0 eV graphene, 0.3-1.5 eV black phosphorus, 1.2-1.9 eV MoS2, etc.), resonant NEMS utilizing ultra-wide bandgap (UWBG) 2D materials or materials with quasi-2D nanostructures have not yet been demonstrated. The adoption of UWBG materials in NEMS resonators could offer new opportunities for interactions with ultraviolet (UV) photons and for high power handling capabilities. This dissertation presents the experimental demonstrations of UWBG resonant NEMS, specifically, hexagonal boron nitride (h-BN) and beta gallium oxide (β-Ga2O3) NEMS resonators, for investigations of both fundamental device physics and engineering of device functions and performance toward the perspectives of technological applications. In this dissertation, the dry transfer techniques in accordance with the analysis in discerning the thin UWBG material flakes are first discussed, followed by the thermal annealing method to boost the resonator performance. Then, experimental demonstration of h-BN 2D nanomechanical resonators vibrating at high and very high frequencies (HF/VHF), and investigations of the elastic properties of h-BN by measuring the multimode resonant behavior of these devices are presented. Following the h-BN resonators, single-crystal β-Ga2O3 nanomechanical resonators using β-Ga2O3 nanoflakes grown via low-pressure chemical vapor deposition (LPCVD) are demonstrated experimentally. From the measurements, multimode resonances and spatial visualization of the multimode motion are resolved to extract the mechanical properties, i.e., material Young’s modulus, EY = 261 GPa, and device built-in stress. The device platform is further applied to the solar-blind UV (SBUV) sensing application. Both resonators and oscillators using suspend β-Ga2O3 nanostructures are constructed and exposed to SBUV irradiation for investigation of SBUV detection based on resonance frequency shift. Further, conventional photo-current-based detection scheme is integrated into the β-Ga2O3 resonator, achieving dual-modality SBUV sensing in the same transducer. Finally, the all-electrical transduction (including both actuation and detection) of mechanical motion of a β-Ga2O3 vibrating channel transistor (VCT) is demonstrated.
Philip Feng (Advisor)
Christian Zorman (Committee Member)
Xiong Yu (Committee Member)
Walter Lambrecht (Committee Member)
165 p.
Electrical Engineering; Engineering; Experiments; Materials Science; Mechanical Engineering; Mechanics; Nanoscience; Nanotechnology; Optics; Physics; Technology
ultra-wide bandgap; beta gallium oxide; hexagonal boron nitride; resonator; oscillator; MEMS; NEMS; sensor; detector; transducer; solar-blind ultraviolet; vibrating channel transistor

Recommended Citations

Citations

  • Zheng, X. (2019). Ultra-Wide Bandgap Crystals for Resonant Nanoelectromechanical Systems (NEMS) [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1554765522327938

    APA Style (7th edition)

  • Zheng, Xuqian. Ultra-Wide Bandgap Crystals for Resonant Nanoelectromechanical Systems (NEMS) . 2019. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1554765522327938.

    MLA Style (8th edition)

  • Zheng, Xuqian. "Ultra-Wide Bandgap Crystals for Resonant Nanoelectromechanical Systems (NEMS) ." Doctoral dissertation, Case Western Reserve University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1554765522327938

    Chicago Manual of Style (17th edition)

case1554765522327938
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© 2019, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.