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Title:Probing local thermal, mechanical, and optical properties utilizing dynamic cantilever response in contact mode atomic force microscopy
Author(s):Rosenberger, Matthew R
Director of Research:King, William P.
Doctoral Committee Chair(s):King, William P.
Doctoral Committee Member(s):Cahill, David G.; Tawfick, Sameh H; Wasserman, Daniel M.
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Atomic Force Microscope (AFM)
High Electron Mobility Transistors
Photothermal Induced Resonance
Contact Resonance AFM
Abstract:Understanding the behavior of materials and devices at the nanometer-scale is important because modern materials and devices have nanometer-scale features. Atomic force microscopy (AFM) is a powerful tool for studying nanometer-scale behavior due to excellent spatial resolution (tip radius < 25 nm) and the ability to measure dynamic surface deformation with sub-picometer precision. Measurement of dynamic surface deformation in response to a stimulus (e.g. heating or mechanical force) provides information about local material properties. This thesis presents three studies which use dynamic surface deformation measurements to investigate nanometer-scale thermomechanical, inverse-piezoelectric, infrared, and mechanical properties. The first study uses AFM to measure thermomechanical and inverse-piezoelectric deformation of biased AlGaN/GaN transistors. Deformation measurements during device heating reveal shifts in the thermomechanical strain fields within devices as bias conditions change. Deformation measurements without heating reveal bias dependence of inverse-piezoelectric deformation. Measurements validate an electro-thermo-mechanical finite element model, which predicts device stress and failure. The second study uses AFM to measure infrared absorption by observing thermomechanical deformation due to infrared light absorption. This thesis describes a novel implementation which enables two orders of magnitude improvement in sensitivity. Measurements of carbon nanotube absorption (diameters near 2 nm) and monolayer graphene demonstrate the effectiveness of this technique. The third study presents the design, fabrication, and implementation of micromechanical contact stiffness devices which provide a range of known contact stiffness. These devices are useful for calibrating dynamic cantilever response as a function of contact stiffness, which is critical for AFM measurements of mechanical properties. This study concludes with the calibration of an AFM cantilever for contact resonance AFM and subsequent measurement of contact stiffness and elastic modulus on three different polymers. The AFM elastic modulus measurements on polymer samples agree with comparable bulk measurements.
Issue Date:2016-10-26
Rights Information:Copyright 2016 Matthew Rosenberger
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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