Advisor(s)

Nicol E. McGruer

Contributor(s)

George G. Adams, Sinan Muftu

Date of Award

2008

Date Accepted

7-2008

Degree Grantor

Northeastern University

Degree Level

Ph.D.

Degree Name

Doctor of Philosophy

Department or Academic Unit

College of Engineering. Department of Electrical and Computer Engineering.

Keywords

Electrical engineering, Nanoelements, MEMS

Subject Categories

Microelectromechanical systems--Design and construction, Nanotechnology

Disciplines

Engineering

Abstract

Three types of MEMS devices were designed, modeled and fabricated. These devices consisted of microhotplates, resonators (angular and horizontal) and uniaxial tensile testers. Different types of test specimens such as metallic thin films, metallic nanowires and electrospun polymer nanofibers were deposited and characterized. Fabrication methods for the devices were developed based on the encapsulation of nanoelements, the anisotropic dry etch of the top Silicon layer of a Silicon-On-Insulator (SOI) wafer and its release by a long wet etch in Buffered-Oxide-Etch (BOE). MEMS microhotplates were designed and fabricated for accelerated lifetime testing of thin films of Cr/Ru/Au, Cr/Ru and Ru as well as nanowires of Ru and RuOx. Rapid thermal cycling at a 1KHz pulse frequency was employed for testing the thin films. Nanowires were characterized using 1KHz and 500Hz pulse frequencies. It was found that the cycling frequency did not influence the nanowire lifetimes in air or in N2. The fabrication of the uniaxial tensile testers and the resonators proved to be a challenge due to stresses within the silicon device layer of the SOI wafers. These problems resulted in difficulties during the release step as well as the end profile of the devices. Even so, devices were fabricated and tested. The resonant frequency of angular resonators was characterized using a frequency sweep of the device. This yielded a resonant peak of 49.152KHz, which differed from the finite element model result (fr=49.4KHz) by 0.5 percent. Uniaxial tensile testers were fabricated and employed in the characterization of PolyEthylene Oxide (PEO) nanofibers. These fibers were deposited on the devices by electrospinning after the device was fully released. The displacements were measured using AFM scans of specially microfabricated markers. It was found that the generated images were not good enough to be employed for Digital Image Correlation (DIC) due to the large number of artifacts. Because of this, the devices display a large uncertainty on the displacement measurements. It was estimated that the fibers had an elastic modulus between 378MPa and 472MPa.

Document Type

Dissertation

Rights Holder

Juan Carlos Aceros Rueda


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