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Title:Quantitative viscoelastic spectroscopy of polymer films using Lorentz force actuated contact resonance atomic force microscopy
Author(s):Bakir, Mete
Advisor(s):King, William P.
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Quantitave Viscoelastic Spectroscopy
Nanomechanical Characterization
Block Copolymers Morphologies
Multi-Frequency Atomic Force Microscopy (AFM)
Cantilever Mathematical Modelling
Contact Resonance Atomic Force Microscopy (AFM)
Abstract:This thesis presents development of a material metrology technique, which is shown to quantify viscoelastic properties of a polymer film within the glass transition region. Designed for nanoscale material characterization applications, heater integrated atomic force microscopy (AFM) cantilever operates in contact resonance mode actuated by externally induced Lorentz force. It is demonstrated that glass transition temperature (Tg) of polymethyl methacrylate (PMMA) film can be detected reproducibly by monitoring contact resonance frequency of the cantilever as a function of temperature. Also, the glass transition temperature is observed in the terms of differential change of cantilever electrical resistance and differential power consumption. Furthermore, employing a harmonic oscillator model to define tip-sample contact interactions, viscoelastic properties of contact stiffness, viscous damping coefficient and elastic modulus for the polymer film are measured as functions of temperature. In addition, multi-frequency actuation for contact resonance is demonstrated providing qualitative material properties. Besides, a mathematical approach is developed to model two-leg and V-shaped LCR cantilevers as in the form of rectangular beam. Finally, local viscoelastic measurements taken on 66-63K PS-PMMA lamellar block copolymer film are presented. Also, nanomechanical surface property mappings of both 37-37K PS-PMMA lamellar and 46-21K PS-PMMA cylindrical block copolymer morphologies are provided. The technique introduced in this work has vast potential to be employed for numerous nano-scale material applications, and eventually replace traditional macro-scale thermophysical material characterization technologies providing local, reproducible and non-destructive analyses.
Issue Date:2014-09-16
Rights Information:Copyright 2014 Mete Bakir
Date Available in IDEALS:2014-09-16
Date Deposited:2014-08

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