Date on Master's Thesis/Doctoral Dissertation

12-2011

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Mechanical Engineering

Committee Chair

Berfield, Thomas Austin

Author's Keywords

PZT; DIC; Thin film; Thermal strain; Sol gel; Adhesion

Subject

Thin films--Thermal properties

Abstract

Lead Zirconate Titanate (PZT), known for its ferroelectric properties, is widely used in micro-electromechanical (MEMS) and nano-electromechanical (NEMS) devices. PZT is a ceramic material that is most commonly found in its sol gel form, which allows for a relatively simple and cost-effective means of deposition and device fabrication. The material properties of PZT have been subject to significant research; however, the material properties of PZT sol gels remain largely unknown. In an effort to further understand thermal strain development, a combination of thermal loading and digital image correlation (DIC) were used to analyze the mechanical response of PZT sol gel films. Additionally, current numerical models are lacking the effects of film adhesion on film failure; therefore, the thermal strain development was analyzed for both well and poorly adhered films. To promote poor adhesion, PZT sol gel films were deposited on a hydrophobic self-assembling monolayer (SAM) and analyzed. Results indicate that a change in mechanical and optical properties of PZT thin films occurs from 200°C to 225°C. The peak strain associated with this point is approximately 61.4% greater in 12-layer films than 3-layer films. Sub-cracking of PZT films occurs after island formed during initial film failure experience an area reduction over 30%. The peak thermal strain development in well adhered 3-layer films is approximately 41.2% greater than poorly adhered films, indicating that adhesion largely dictates film failure. The 3-layer and 12-layer poorly adhered films fail at temperatures within 2% percent of each other despite varying surface strain fields, indicating the strain magnitude at the interface drives film failure.

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