We have studied the LME phenomenon for the Cu/Hg couple, from an experimental and a computational point of view. We compared the LME behavior of standard oxygen free high conductivity (OFHC) copper with Grain Boundary Engineered (GBE) copper (containing a high fraction of special Σ3 GBs). Experimentally, we find that special Σ3 GBs in copper are less prone than general GB to LME by liquid mercury. In parallel, we have investigated the difference in LME induced fracture between the symmetric Σ3(111)[110]70.5° tilt GB and the symmetric Σ5(210)[100]36.87° tilt GB by ab-initio calculations. The Hg segregation trend has been evaluated for these 2 GBs. Ab-initio tensile tests on the Σ3(111) GB with and without segregated Hg atoms have been performed. Finally solid/liquid interfaces have been modeled using ab-initio molecular dynamics (AIMD) in order to calculate solid-liquid surface energies (γSL). Using a Griffith approach, we have evaluated the energy difference γGB - 2 γSL. The LME mechanism in Cu/Hg is discussed.

Grain boundary (GB) sliding is an important deformation mode in polycrystals, and it has been extensively investigated, for example, there are many studies on influences of the atomic geometry in the GB region. However, it is important to investigate GB sliding from the electronic structure of GB for deeper understandings of the sliding mechanisms. In the present work, we investigated the GBs sliding in pure and segregated bicrystals with classical molecular dynamics (MD) simulations and first-principles calculations. It is accepted that the sliding rate is affected by the GB energy. However, there was no correlation between the sliding rate and the GB energy in either the pure or the segregated bicrystals. First-principles calculations revealed that the sliding rate calculated by the MD simulations increases with decreasing minimum charge density at the bond critical point in the GB. This held in both the pure and segregated bicrystals. It seems that the sliding rate depends on atomic movement at the minimum charge density sites.

The surface morphologies of AlGaN/AlN/GaN HEMT structures were examined by using the atomic force microscopy (AFM).These HEMT structures have been grown by metalorganic chemical vapor deposition (MOCVD) onto the sapphire (0001) substrates where the thicknesses of AlN interlayers were varied from 0 to 5 nm. After the growth of GaN buffer layer, the AlN intermediate and AlGaN top layers were subsequently deposited at 1130°C in an trimethylaluminum (TMAl) and ammonia (NH3) atmosphere. The surface of AlGaN layers shows the thick- and fine-thread patterns.

It was found that the root-mean-square (RMS) roughness of the samples with 0, 0.5, 2.5 and 5nm AlN interlayer thickness are 0.503, 0.534, 0.534 and 0.601nm, respectively. Although the cracks and rougher surfaces show that the qualities of AlGaN barrier layers have slightly degraded in the samples with thicker AlN layer. These phenomena could be attributed to the lattice mismatch and the growth temperature. In addition, the room-temperature two-dimensional electron gas (2DEG) mobility and density analysis were performed on the AlGaN surfaces and the measured results were discussed in detail.

It is frequently observed that as-grown single-walled carbon nanotubes (SWCNTs) contain defects. Controlling the defect density is a key issue for the control of nanotube properties. However, little is known about the influence of the growth conditions on the formation of nanotube defects. In addition, SWCNT samples frequently contain carbonaceous by-products which affect their ensemble properties. Raman spectroscopy is commonly used to characterize both features from the measurement of the defect-induced D band. However, the contribution of each carbonaceous species to the D band is usually not known making it difficult to separately extract the defect density and relative abundance of each. Here, we report on the correlated evolution of the D and G’ bands of SWCNT samples with increasing growth temperature. In the general case, three to four Lorentzian components are required to fit them. Coupled with HRTEM characterization, the low frequency components of the D and G’ can be attributed to the contribution of SWCNTs while high frequency components are associated with defective carbonaceous by-products. The nature of these defective by-products varies with the type of catalysts and with the growth conditions.

The growth mechanism of large-size domains in PbTiO3/SrTiO3 heteroepitaxial thin films was examined using annular bright field (ABF) – scanning transmission electron microscopy and geometric phase analysis (GPA). {101} domain walls surrounded 90° domains. The large 90° domain grows by the coalescence of the nano-size domains of less than 5 nm width. A strain map obtained from the GPA of ABF-STEM image showed that 90° domains interacted elastically and attractively with edge dislocations at PbTiO3/SrTiO3 interface through simple shear strain.

The effect of the continuously inserted 3-nm-thick Co(Pt) layer on the preferred orientation of AlN film is investigated, and highly c-axis textured AlN film has been obtained. According to high resolution transmission electron microscope observations, the preferred orientation of sputter-deposited AlN film is improved from polycrystalline to (001) texture at the interface between AlN and Co(Pt)(111). The texture of AlN films are also examined using an x-ray diffractometer equipped with a two dimensional positive sensitive detector. The x-ray rocking curve full width at half maximum of 002AlN of (001) textured AlN with the Co(Pt) layer is 2.7°, and the residual stress of such specimen is 1.6 GPa in tensile stress.