Theoretical Analysis Of Carbon Nanotube Strain Sensor And Micro-Raman Strain Measurement Technique

In recent years, the development of micro/nano science and technology induces a requirement for new experimental methods to measure the mechanical properties of micro-system. Due to the investigating progress about the Raman effect of carbon nanotubes (CNTs), it is possible to study the mechanical parameters of the Raman-inactive materials by taking CNTs as sensing media.Based on H.D. Wagner's work about CNT Raman sensor, a new measurement theory of carbon nanotube strain sensor is presented. In this theory, the CNTs are taken as strain sensor. Through theoretical derivation, the analytic relationship between plane-strain components and the Raman-shift of any appointed polarization direction is achieved by utilizing the Raman characteristics of CNTs such as the sensibility of Raman shift to strain, resonance polarization Raman, and by taking CNTs Raman effects of all the directions into account. Comparing with the relative work of Wagner, the measurement theory in this thesis can describe the strain components of any direction on the surface of the deformable solid body under any loading state. Besides, it is widely applicable to multiform modes of Raman experiments.A micro-measuring technique of Raman Strain Rosette is proposed based on the theory of carbon nanotube strain sensor above. This technique can be used to obtain the plane-strain components, the normal strainεx,εy and the shear strainγxy, of a sample in micro-scale or smaller by measuring the Raman-shifts in three appointed polarization directions and then applying the equations set of Raman strain rosette. The experiments in this thesis prove that the measurement theory of carbon nanotube strain sensor is correct. Furthermore, the technique of Raman strain rosette extend the limitation of the traditional Raman technique of strain measurement in Engineering application, since it is practicable to achieve the (normal and shear) strain components of not only Raman-active but also Raman-inactive materials by taking CNTs attached on the surface of, or doping them inside, the sample as strain sensors. Besides, this technique is also feasible to measure the distributing fields of strain in micro-regions.The Micro-Raman strain/stress measurement technique is applied on the studies of several micro-region and micro-system problems in this thesis. The distribution regularity of intrinsic residual stress in deepness direction of porous silicon is studied by applying Raman line mapping. The effect of dynamic capillarity on stress transformation in porous silicon is analyzed by Real-time Raman experiments. The processing residual stress inside the SiO2/Au films and their Si base-wafer introduced in different steps of process scheduling is investigated, and a multi-layer model of Si wafer induced by thermal oxidization is proposed. Besides, the stress transfer of single fiber/microdroplet structure and the strain fields and stress fields in the matrix abound a fiber inside the short-fiber composite are measured by utilizing the Raman strain rosette technique.