Evaluation of length scale effects for micro and nano-sized cantilevered structures

This thesis focuses on evaluating the length scale effects for micro and nano-sized silicon cantilever experimentally, and incorporating the length scale effects into the conventional natural frequency and static deflection models of these cantilevers. Experiments were conducted to demonstrate that the models incorporating length-scale effect estimate the natural frequency and static deflection of the cantilevers more accurately. Micro and nano indentation experiments were conducted to determine the length-scale factors for micro and nano-sized silicon cantilevers. Geometrically necessary dislocations (GND) and the strain gradient theory is used to analyze the experimental data and subsequently to calculate the micro and nano length-scale factors using two different length-scale factor estimation methods reported in the literature. The factors match well with each other that both methods are equally valid to estimate the factors of silicon micro and nano cantilevers. Optical lithography and pulsed laser deposition methods were attempted to fabricate the micro silicon cantilevers with encouraging outcomes to use these techniques to make the cantilevers. AFM cantilevers were used as the micro and nano cantilevers to measure their static deflection in order to compare the results calculated from the analytical model incorporating the length-scale factor. The stiffness of the experimental cantilevers were determined experimentally using an AFM in order to determine the real natural frequency of the micro and nano cantilevers. The results presented demonstrate that the length scale-factor should be considered in estimating the natural frequency, static deflection and stiffness of the micro and nano-sized cantilevers more accurately, which are the building blocks of micro and nano-electromechanical systems (MEMS and NEMS). One application of such cantilevers is to use them as chemical, medical, gas or force sensors based on measuring their static deflection and the change in their resonant frequency