Polycrystalline diamond films have been patterned on Si3N4 Si and SiO2 Si substrates by selective seeding with a double-layer mask via hot-filament chemical vapor deposition. High quality in the patterned diamond films and high selectivity were obtained by the process. The diamond films deposited on the insulators at different CH4 H2concentrations were studied by scanning electron microscopy and Raman spectroscopy. The process proved to be far less damaging to the substrates, and yet effective in developing patterns of diamond films on a large and different substrate. 2001 Elsevier Science B.V. All rights reserved.

One-dimensional (1D) nanowires, two-dimensional (2D) nanodendrites, and three-dimensional (3D) nanochains of SnO2 have been grown on single silicon substrates by Au-Ag alloying catalyst assisted carbothermal evaporation of SnO2 powders. One-dimensional twinning crystalline nanowires, 2D nanodendrites with spidery structure, and 3D nanochains with zigzag structure were reported. Three new peaks at 370, 470, and 555 nm in the measured photoluminescence spectra were observed, implying that more luminescence centers exist in SnO2 nanostructures due to nanocrystals and defects. The growth of the SnO2 nanostructure was discussed on the basis of the vapor-liquid-solid (VLS) mechanism.

The size-dependent thermodynamic and kinetic model was established to elucidate the physical and chemical origin of the thermodynamic driving force causing the spontaneous interfacial alloying and the anomalous diffusion rising from the metallic core-shell interface in nanoparticles. It is found that, in thermodynamic, the giant driving force from the size-dependent mixing enthalpy and interfacial energy leads to the spontaneous interfacial alloying. In kinetic, the unusually intensive interfacial diffusion provides a path to achieve the interfacial alloying at the ambient temperature. The theoretical predictions are in agreement with experimental data.

Considering the effect of the electrostatic energy on the phase stability of binary alloying nanoparticles, we proposed a charge-dependent thermodynamic model to address the phase transformation between miscible and immiscible when the size of alloying particles goes into the nanometer scale. We found that the miscible system would transform into immiscible when the size of alloying nanoparticles reduces to a critical size. Surprisingly, the system would return miscible from immiscible again when the size further reduces to less than the critical size. The physical and chemical origin of the anomalous transition between miscible and immiscible was pursued.

With the aim of understanding the thermal stability of binary immiscible metallic multilayers, we propose a generally size-dependent thermodynamic criterion for determining the interface alloying in multilayers, with respect to the size-dependent interface energy of binary metal systems. Taking the copper/tungsten bilayer as an example, we obtain the interfacial alloying phase diagram based on the proposed thermodynamic model. Our theoretical predictions are consistent with experiments, implying that the size-dependent thermodynamic criterion of the thermal stability could be expected to be applicable to many multilayers.

Aiming at synthesis diamond nanowires, a simple thermodynamic approach was performed with respect to the effect of nanosizeinduced additional pressure on the Gibbs free energy of critical nuclei to elucidate diamond nucleation inside carbon nanotubes upon chemical vapor deposition, based on the carbon thermodynamic equilibrium phase diagram. Notably, these analysis showed that the diamond nucleation would be preferable inside a carbon nanotube due to the effect of surface tension induced by the nanosize curvature of the carbon nanotube and diamond critical nuclei, compared with diamond nucleation on the flat surface of a silicon substrate. Meanwhile, the metastable phase region of diamond nucleation would be driven into a new stable phase region in the carbon thermodynamic equilibrium phase diagram by the effect of nanosize-induced additional pressure. Eventually, we predicted that carbon nanotubes would be an effective path to grow diamond nanowires by chemical vapor deposition.

ZnO nanowires were fabricated on the amorphous diamond thin layer on silicon substrates using thermal chemical vapor transport and condensation (CVTC) without any metal catalysts. The remarkable enhancement of the field emission of the nanocomposites by ZnO nanowires covered amorphous diamond was found compared to that of the intrinsic amorphous diamond, suggesting the probability of decorating amorphous diamond by fabricating one-dimensional nanostructures on its surface, which could largely improve the field emission by modifying surface microstructures. Associated with surface chemical reactions, a vapor-solid mechanism of ZnO nanowires nucleation and growth on amorphous diamond was established.