Clark T.-C. Nguyen (Advisor)

A micromechanical structure for on-chip strain sensing maps strain-induced gap changes to resonance frequency shifts while employing differential strategies to null out bias uncertainty, all towards repeatable measurement of sub-nm displacement changes that equate to sub- strain increments. The key enabler here is the use of gap-dependent electrical stiffness to shift resonance frequencies as structural elements stretch or shrink to relieve stress. An output based on the difference frequency between two close proximity structures with unequal stress arm lengths (cf. Fig. 1) removes...

Single-digit-nanometer electrode-to-resonator gaps have enabled 200-MHz radial-contour mode polysilicon disk resonators with motional resistance Rx as low as 144 while still posting Q’s exceeding 10,000, all with only 2.5V dc-bias. The demonstrated gap spacings down to 7.98nm are the smallest to date for upper-VHF micromechanical resonators and fully capitalize on the fourth power dependence of motional resistance on gap spacing. High device yield and ease of measurement debunk popular prognosticated pitfalls often associated with tiny gaps, e.g., tunneling, Casimir forces, low yield,...

Microelectromechanical system (MEMS)-based oscillators are in the heart of many of our electronic devices today, forming the timing basis for our increasingly higher frequency circuits. High-performance, low-noise oscillators are critical to meeting the standards of today's communication protocols. Effects of noise from all inputs of a circuit to the final output spectrum should be understood to make better oscillators, and this report specifically considers the effects of noise on the bias voltage supply needed for strong electromechanical coupling to sustain resonance. We investigate how...