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In this work, we develop further the microbridge testing method by deriving a closed formula of deflection versus load, which is applied at an arbitrary position on the microbridge beam. Testing a single beam at various positions allows us to characterize simultaneouslyYoung's modulus and residual stress of the beam. The developed method was then used to characterize the mechanical properties of GaN thin films on patterned-Si (1 1 1) substrates grown by metal organic chemical vapor deposition (MOCVD). The microbridge samples were fabricated by using the microelectromechanical fabrication technique and tested with a nanoindentation system. Young's modulus and residual stress of the GaN films were determined to be 287 +/- 190 GPa and 851 +/- 155 MPa, respectively. In addition, alternative measurements of the residual stress, Young's modulus and hardness of the GaN films, were conducted with micro-Raman spectroscopy and the nanoindentation test, yielding the corresponding values of 847 +/- 46 MPa, 269.0 +/- 7.0 GPa and 17.8 +/- 1.1 GPa.

The Energy-Dispersive-X-ray-based permeation and oxidation test has been further developed by an improved theoretical analysis, in which chemical potential gradients rather than concentration gradients are employed. The developed test is able to characterize diffusion kinetics in diffusion barriers at the nanometer scale. The Cu flux coefficient in (Cu, Ni)(3)Sn intermetallic compound nanolayers was determined from the test to be 8.48 x 10(-15) mol.(m.s.J/mol)(-1) exp(-52.3 kJ.mol(-1)/RT) in a temperature range of 250 degrees C-400 degrees C. (C) 2009 Elsevier B.V. All rights reserved.

Dendrite-like ZnO@Ag heterostructure nanocrystals are designed and fabricated by a facial two-step chemical method in a large scale. The heterostructure nanocrystals are composed of single crystal Ag nanowires as trunks and highly dense (0001) oriented ZnO nanorods as branches. ZnO nanorods with diameters of about 50-400 nm are vertically grown on the six lateral surfaces of the Ag nanowires. Ultrathin ZnO nanowires or nanotubes with a diameter of less than 30 rim are decorated on the ZnO nanorods. The photocatalysis test shows that the ZnO@Ag heterostructures exhibit a higher photocatalytic activity than the pure ZnO nanorods, thereby implying that the Ag/ZnO interfaces promote the separation of photogenerated electron-hole pairs and enhance the photocatalytic activity.

The present work conducts crystal characterization by High Resolution Transmission Electron Microscopy (HRTEM) on Cu/Sn-nanolayer/Ni sandwich structures associated with the use of Energy Dispersive X-ray (EDX) analysis. The results show that DO22-(Cu,Ni)(3)Sn intermetallic compound (IMC) ordered structure is formed in the sandwich structures at the as-electrodeposited state. The formed DO22-(Cu,Ni)(3)Sn IMC is a homogeneous layer with a thickness about 10 nm. The DO22-(Cu,Ni)(3)Sn IMC nanolayer is stable during annealing at 250 degrees C for 810 min. The formation and stabilization of the metastable DO22-(Cu,Ni)(3)Sn IMC nanolayer are attributed to the less strain energy induced by lattice mismatch between the DO22 IMC and fcc Cu crystals in comparison with that between the equilibrium DO3 IMC and fcc Cu crystals. (C) 2009 Elsevier B.V. All rights reserved.