Papers by Author: Ching Kong Chao

Abstract: This work characterizes the mechanical and opto-electric properties of Aluminum-doped zinc oxide (AZO) thin films deposited by atomic layer deposition (ALD), where various depositing temperature, 100, 125, 150, 175, and 200 °C are considered. The transmittance, microstructure, electric resistivity, adhesion, hardness, and Young’s modulus of the deposited thin films are tested by using spectrophotometer, X-ray diffraction, Hall effect analyzer, micro scratch, and nanoindentation, respectively. The results show that the AZO thin film deposited at 200 °C behaves the best electric properties, where its resistance, Carrier Concentration and mobility reach 4.3×10^-4 Ωcm, 2.4×10²⁰ cm^-3, and 60.4 cm²V^-1s^-1, respectively. Furthermore, microstructure of the AZO films deposited by ALD is much better than those deposited by sputtering.

Abstract: Solution of a crack interacting with a tri-material under a remote shear load for anti-plane elasticity problem is considered in this paper. The main purpose of this work is to study the interaction between a crack and a tri-material for anti-plane elasticity problem. This can be achieved by determination of the stress intensity factors that allow the characterization of this interaction from the point of view of linear elastic fracture mechanics. The proposed method is based on complex variable solution of a screw dislocation together with logarithmic singular integral equations. The singular integral equation is then solved numerically by modeling a crack in place of several segments. Some numerical results are performed to show the effects of material property combinations and geometric parameters on the normalized mode-III stress intensity factors. The results show that the stiffer materials may always give retardation effect on stress intensity factors when a crack approaching interfaces. On the other hand, the softer materials may always give enhancement effect on stress intensity factors.

Abstract: A procedure for fabricating a periodic structure on a metal at submicron order using holographic interferometry and molding processes is described. First, holographic interference using a He-Cd (325nm) laser is used to create the master of the periodic line structure on an i-line sub-micron positive photoresist film. A 200nm nickel thin film is then sputtered onto the positive photoresist. Pattern is then transferred to a metal using Nickel-Cobalt electroforming. Initial results show the technique can accurately control the grating’s period and depth.

Abstract: Theoretical and experimental methods dealing with the effect of a viscoelastic substrate on a cracked body under inplane load are presented in this article. A generalized trimaterial solution is solved as a convergent series in terms of complex potentials via the successive iterations of the alternating technique in order to satisfy the continuity condition along the interfaces between dissimilar media. This trimaterial solution is then applied to the problem of a finite thickness layer bonded to a half-plane substrate. Using a standard solid model to formulate the viscoelastic constitutive equation, the real time stress intensity factors can be directly obtained from the Laplace domain. In the experiment, an aluminum cracked plate bonded to a polymer substrate is tested in a tension machine, where the displacement of the specimen is recorded by a high precision digital camera. The time-dependent stress intensity factor is determined by an inverse calculation through the crack opening displacement. The comparisons between the theoretical and experimental results are discussed in the final.

Abstract: A new means of transducing mechanical force using a diffractive Bragg grating based polymeric sensor is presented. The diffraction gratings are successfully fabricated on a polydimethylsiloxane (PDMS) polymer using the holographic interference and micromolding technique. The micro MTS tensile test incorporated with the Raman experiment showed that a relationship between the load and the observed diffraction pattern shift could be obtained. The results show an excellent correlation between the optical measurements and load with a sensitivity of 0.05N.