Date of Award
8-1-2012
Document Type
Dissertation
Degree Name
Ph.D.
Organizational Unit
Daniel Felix Ritchie School of Engineering and Computer Science
First Advisor
Siavash Pourkamali, Ph.D.
Second Advisor
James C. Wilson
Third Advisor
Corinne Lengsfeld
Fourth Advisor
Mohammad Matin
Keywords
Mass sensors, MEMS (Micro Electromechanical Systems), Nano-Balances, NEMS (Nano Electromechanical Systems), Oscillators, Resonators
Abstract
As the potential emerging technology for next generation integrated resonant sensors and frequency references as well as electronic filters, micro-electro-mechanical resonators have attracted a lot of attention over the past decade. As a result, a wide variety of high frequency micro/nanoscale electromechanical resonators have recently been presented. MEMS resonators, as low-cost highly integrated and ultra-sensitive mass sensors, can potentially provide new opportunities and unprecedented capabilities in the area of mass sensing. Such devices can provide orders of magnitude higher mass sensitivity and resolution compared to Film Bulk Acoustic resonators (FBAR) or the conventional quartz and Surface Acoustic Wave (SAW) resonators due to their much smaller sizes and can be batch-fabricated and utilized in highly integrated large arrays at a very low cost.
In this research, comprehensive experimental studies on the performance and durability of thermally actuated micromechanical resonant sensors with frequencies up to tens of MHz have been performed. The suitability and robustness of the devices have been demonstrated for mass sensing applications related to air-borne particles and organic gases.
In addition, due to the internal thermo-electro-mechanical interactions, the active resonators can turn some of the consumed electronic power back into the mechanical structure and compensate for the mechanical losses. Therefore, such resonators can provide self-sustained-oscillation without the need for any electronic circuitry. This unique property has been deployed to demonstrate a prototype self-sustained sensor for air-borne particle monitoring.
I have managed to overcome one of the obstacles for MEMS resonators, which is their relatively poor temperature stability. This is a major drawback when compared with the conventional quartz crystals. A significant decrease of the large negative TCF for the resonators has been attained by doping the devices with a high concentration of phosphorous, resulting in even slightly positive TCF for some of the devices. This is also expected to improve the phase noise characteristics of oscillators implemented utilizing such frequency references by eliminating the sharp dependence to electronic noise in the resonator bias current.
Finally it is well known that non-uniformities in fabrication of MEMS resonators lead to variations in their frequency. I have proposed both active (non-permanent) and permanent frequency modification to compensate for variations in frequency of the MEMS resonators.
Publication Statement
Copyright is held by the author. User is responsible for all copyright compliance.
Rights Holder
Arash Hajjam
Provenance
Received from ProQuest
File Format
application/pdf
Language
en
File Size
145 p.
Recommended Citation
Hajjam, Arash, "Thermally Actuated Resonant Silicon Crystal Nanobalances" (2012). Electronic Theses and Dissertations. 262.
https://digitalcommons.du.edu/etd/262
Copyright date
2012
Discipline
Electrical engineering, Nanotechnology, Mechanical engineering