Noncontact Adhesion and Mechanical Properties Characterization of Nano and Micro-Scale Structures Interacting with Elastic Waves.

摘要

At nano/micrometer scales, adhesion, a weak intermolecular interaction (van der Waals force), compared to several other type of forces often dominates the deformation and mechanics of nano/micro-scale structures. Accurate adhesion characterization of nano/micro-scale particles and thin-films (nm-scale) with various substrates is critically important in various industries. In semiconductor industries, understanding and characterizing particle-substrate adhesion bond and interfacial adhesion of thin films plays a critical role in fabricating defect-free structures. In this dissertation, ultrasonic-based techniques along with novel mathematical models are introduced to accurate adhesion energy characterization of nano/micro-scale particles and thin-films (Graphene layer is used as thin-film) in a non-contact manner. In the case of nano/micro-scale particles adhesion characterization, particle-substrate adhesion bond is characterized based on complex vibrational dynamics of micro-spherical particles on flat substrates subjected to ultrasonic base excitations. In the thin-films adhesion characterization case, the interfacial adhesion energy between thin films and various substrates is extracted based on the micro-spherical particles complex dynamics affected by the presence of thin-films on the vibrating substrates. Also in order to study the anisotropic adhesion properties and the rolling dynamic of nano/micro-scale particles as the most important dynamic in particle removal techniques, a novel non-contact manipulation/transport technique is introduced. In this technique, Surface Acoustic Wave (SAW) fields are employed to roll the particles on dry substrates in a non-contact manner in order to eliminate the inaccuracies and undesirable property modifications of contact-based techniques. Adhesion and mechanics of nano/micro-scale objects is affected by the viscoelastic properties of the contacting materials. Therefore, a novel and non-destructive technique along with a mathematical model is introduced to characterize the mechanical properties of solid materials based on the attenuation and dispersion of ultrasonic waves propagating in a medium. Further, in order to increase the adhesion measurements in the introduced in vibrational spectroscopy-based technique, thermoelastic damping as an important internal loss mechanism of elastic waves in nano/micro-scale structures is introduced and potential applications of smart materials to control this loss mechanism is discussed theoretically. Also at nano/micro-scale levels, size effect phenomena affect the mechanics of structures which cannot be explained with classical elasticity theories. Therefore, a higher order elasticity theory is adopted to study the thermoelastic damping at nano/micro-scales (such as vibrating adhesion bond and nano-film layers). Finally, potential applications of the discussed works are identified.