Diamond nucleation by biased hot filament chemical vapor deposition was investigated by scanning electron microscopy and atomic force microscopy. It was found that a number of microdefects were produced on a substrate surface owing to energetic ion bombardment under negative substrate bias, which increased with increasing negative bias. The nucleation density was enhanced with an increase of negative bias. During diamond nucleation, a purple glow was observed when the negative bias was increased to a critical value. At the onset of glow discharge, the process of diamond nucleation on a silicon surface by biased hot filament chemical vapor deposition was theoretically studied by analysis of the experimental results of diamond nucleation. The relationship among the number of active ions, the microdefects, and nucleation density with negative bias was given by reasonable analytic formulas. The effect of negative bias on ion diffusion on the substrate surface was theoretically researched and deduced. The influence of negative bias on the bond strength of diamond nuclei on the substrate was analyzed theoretically. The adhesion force between diamond nuclei and the substrate surface was measured by means of the scratch surface method, which was in accord with theoretical consideration. The results indicated that the theoretical calculation was in agreement with experimental results.

The functionalization of carbon nanotubes (CNTs) was carried out by using different chemical treatment methods. These functionalized CNTs were characterized by TEM image and FT-IR spectra. The CNT electrodes are measured by thermal resistivity and cyclic voltammetry experiments. The results showed that two important factors controlled the electrochemical properties of the CNT film electrode: one is the active functional group; another is activation energy of the CNT film. From our experiments, we have found the electrode of 10min nitric acid treated CNTs have the optimal peaks in relation to carboxylic acids, the highest redox peak currents, the biggest value of k0 and welldefined quasi-reversible voltammograms for redox of iron couples, in which the two factors best match.

The Pr55-xAl12+xFe33−yCuy (0≤x≤5, 0≤y≤8) bulk metallic glasses (BMGs) 5mm in diameter and 100 mm in length were prepared by copper mold suction casting. Hysteresis loops of the Pr55−xAl12+xFe33−yCuy BMGs and the corresponding Pr55Al12Fe30Cu3 crystallized alloy were measured, and the results showed that the Pr55−xAl12+xFe33−yCuy BMGs are hard magnetic, while the completely crystallized Pr55Al12Fe30Cu3 alloy is paramagnetic at room temperature. The thermal behavior and crystallization of the Pr55Al12Fe30Cu3 BMG were studied by differential scanning calorimetry, and the results indicated that the Pr-based BMG has obvious glass transition and a wide supercooled liquid region up to 75K. The crystallization activation energy for the Pr55Al12Fe30Cu3 BMG is much smaller than that of Zr-Ti-Cu-Ni-Be BMG.

Magnetoresistive effects were studied in p-type heteroepitaxial diamond films with a strip or Corbino disk structure in a magnetic field ranging from 0 to 5 T. The films were grown by microwave plasma chemical vapor deposition and boron doped by cold ion implantation and rapid thermal annealing. The experimental results show that the magnetoresistance (MGR) of p-type heteroepitaxial diamond films strongly depends on the geometric form of the samples and the magnetic field. Diamond films are assumed to be an isotropic isothermal solid in which conduction is by holes from light, heavy and split-off bands. Based on the Fuchs and Sondheimer thin-film theory, considering spherical energy surfaces and mixed scattering by lattice vibrations and ionized impurities and surface, a theoretical description of the magnetoresistive effect in diamond films is presented by solving the Boltzmann transport equation in the relaxation time approximation. A relationship between the MGR and the thickness of films, magnetic field, and mobility is shown.

A rare-earth Pr-based bulk metallic glass (BMG) is obtained in the shape of rod up to 5mm in diameter by die cast. Unlike other rare-earth-based BMGs, it exhibits a distinct glass transition, the low glass transition temperature (Tg5409 K), a large and stable supercooled liquid region, and paramagnetic property. The glass transition as well as its kinetic nature and the fragility parameters of the BMG have been studied. The BMG offers an ideal model to investigate the nature of glass transition as well as the relaxation and nucleation with a large experimentally accessible time and temperature window at low temperatures.

In this article, the diameter distributions of carbon nanotube were theoretically analyzed. The carbon nanotubes were grown by microwave plasma enhanced CVD. For studying the diameter distributions of the carbon nanotubes, the thermodynamic transformation of catalytic films was theoretically considered. Therefore, a process of the formation of stable catalytic islands was supposed, in which the initial continuous catalytic films were first transformed into many critical nuclei and then became stable islands through diffusion of the critical particles, where carbon nanotubes just grew up. The island distribution expression can be derived, and under certain conditions, carbon nanotubes have similar distributions. The nanotubes grown on different catalyst films were analyzed, which showed that the nanotubes over thick films have broad diameter distributions and large mean diameters, while that over thin films have narrow diameter ranges and small diameters on average. The theoretical results were in good agreement with the experimental data.

The process of diamond nucleation by hot filament chemical vapor deposition was investigated by atomic force microscopy. It was observed that a large number of micro-defects (pits) were produced on the surface of the silicon substrate due to ion bombardment under the negative potential and diamond nucleated on the pits. The formation of the pits and their role in diamond nucleation were theoretically approached. The results indicate that the number of the pits increased with increasing potential, the diamond nucleation density and the nucleation rate were functions of the pits, and they were in agreement with the experiment results.

Diamond films have been deposited on AlN substrates using hot filament chemical vapor deposition. By applying a negative bias voltage, a high diamond nucleation density on AlN substrates as high as 10 10 cm-2 has been realized. The appearance of bias current and plasma induced on the AlN surface was found critical for the enhancement of diamond nucleation density. Satisfactory adhesion of the deposited diamond films with the AlN substrates has been achieved for application purposes. q2000 Elsevier Science B.V. All rights reserved.

Nucleation and growth of diamond films on aluminum nitride (ALN) coatings were investigated by scanning electron microscopy, Raman spectroscopy and scratch test. ALN films were grown in a magnetron sputtering deposition. The substrates were Si(111) and tungsten carbide (WC). Chemical vapor deposition (CVD) diamond films were deposited on ALN films by hot filament CVD. The nucleation density of diamond on ALN films was found to be approximately 10 5cm 2, whereas over 10 10cm2 after negative bias pre-treatment for 35min was 320V, and 250mA. The experimental studies have shown that the stresses were greatly minimized between diamond overlay and ALN films as compared with WC substrate. The results obtained have also confirmed that the ALN, as buffer layers, can notably enhance the adhesion force of diamond films on the WC.

The magnetoresistance effect of p-type diamond films has been investigated at different temperature. Diamond films were grown by microwave plasma chemical vapor deposition. Mirror-polished p-type Si(100). was used as a substrate material. The experimental results show that a notable magnetoresistance effect in polycrystalline and heteroepitaxial semiconducting diamond films was observed. The relative changes in the resistivity of the diamond films with magnetic field strongly depended on both boron-doped concentration in the films and geometric form of the samples. The effect of disk structure was greater than that of strip-type samples, also variation in the resistivity of heteroepitaxial diamond films was greater than that of polycrystalline diamond films at same magnetic field. The magnetoresistance of p-type diamond films was decreased with increasing both boron-doped concentration and temperature. The relative changes in resistance of the heteroepitaxial diamond films with the disk structure was increased by 0.85 at room temperature under magnetic intensity of 5T, but only 0.40 for strip-type structure. The results are discussed in detail.