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Auger electron spectroscopy has been used to identify the allotropes of carbon in chemical vapour deposited diamond films deposited on copper and tungsten wires and on SiC and silica fibres and to measure the thickness and composition of the diamond/substrate reaction layers. The significance of these results for the manufacture of diamond fibres i...
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A solution of the tungsten imido guanidinato complex W(NiPr)Cl3[iPrNC(NMe2)NiPr] (1) in benzonitrile was used to deposit tungsten nitride carbide (WNxCy) thin films by chemical vapor deposition in the temperature range of 400–750 °C. Films grown with 1 were composed of W, N, C, and O as determined by Auger electron spectroscopy. X-ray photoelectron...
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... Prior to the deposition of diamond, it is imperative to figure out the poor adhesion between diamond and Cu, which is due to their lattice mismatch and the difference of the thermal expansion coefficients [36,37], plus the fact that no interfacial carbide layer can be formed as "glue" at the interface [38,39]. Based on our previous work [40,41] and the optimization of interlayer (Mo, W, Cr and Ti) and deposition parameters, Cr was chosen as interlayer for the deposition of diamond on Cu foams by the DC magnetron sputtering technique. ...
Three-dimensional porous diamond foam with high quality was fabricated. • Paraffin-based phase change materials incorporated with diamond foam were synthesized. • Thermal conductivity of the composite was significantly enhanced. • The enhancement was attributed to the interconnected diamond networks with high thermal conductivity. • Improved shape stability and good thermal reliability were achieved. A B S T R A C T For thermal energy storage applications using phase change materials (PCMs), the power capacity is often limited by the low thermal conductivity (λ PCM). Here, a three-dimensional (3D) diamond foam (DF) is proposed by template-directed chemical vapor deposition (CVD) on Cr-modified Cu foam as highly conductive filler for paraffin-based PCM. Results showed the foam substrate was completely covered by continuous diamond films with high quality. And it showed a faster thermal response than that of Cu foam (CF) and Cu disc, while only a little slower than that of free-standing diamond disc with the same thickness. The incorporation of interconnected diamond foam with the diamond volume fraction of only 1.3% in the composite phase change material represented a great thermal conductivity enhancement over the pure paraffin, CF/paraffin and diamond particles reinforced paraffin by a factor of 25.8, 1.62 and 13.88, respectively. The great enhancement of the thermal conductive property was mainly attributed to interconnected diamond networks with high thermal conductivity, which effectively reduced the phonon-phonon and phonon-boundary scatterings. Besides, the DF/ paraffin composite PCM exhibited an improved shape stability and a fast heat charging rate with the latent heat of 124.7 J/g. The marriage of the excellent properties of diamond and the inherent advantages of the 3D interconnected structure makes the diamond foams potential components or act as reinforcements in the field of high-efficiency heat dissipation and thermal energy storage.
... Because of the large mismatch of thermal expansion coefficients between Cu and diamond [46] and the fact that no interfacial carbide layer is formed at the start of the CVD process [47,48], diamond films that were directly deposited on Cu substrates suffer from poor adhesion. To solve this problem, Cr can be a suitable and commonly-used interlayer material for enhancing diamond nucleation, producing adherent diamond films on Cu substrates as well as improving the high-temperature stability of the Cu foam during the CVD deposition [49,50]. ...
Diamond with a 3D porous macrostructure has a combination of outstanding intrinsic physicochemical properties and unique structural advantages, which is highly promising for wide-scale practical applications. In this paper, a novel macroscopic porous structure of diamond foam (DF) prepared by hot filament chemical vapor deposition (HFCVD) is proposed for thermal management. The continuous diamond film coated on macroporous Cu foam (CF) substrate forms a monolith of 3D interconnected diamond network, which can act as an effective conductive highway for heat transfer, leading to an exceptional thermal transport property significantly superior to that of CF. Then, DF was further infiltrated with epoxy resin as a thermal conducting filler through the vacuum impregnation process. The thermal conductivity of DF/epoxy composite significantly increased up to 10-fold from 0.23 (neat epoxy) to 2.28 W/m K even with a fairly low diamond loading of 1.2 wt%. The further finite element analysis indicates that the formation of 3D interconnected heat conduction network is advantageous to dissipate heat efficiently in practical application. This work opens up new opportunities toward realizing the application of macroporous DFs and their composites for the use in heat dissipation and the future development of high-performance thermal management systems.
... The first one is that the Auger energy of the hydroxyl group is very low. It is considerably lower than that of diamond, both of the natural one (269.5-270.7 eV) [19,20]) and of the CVD diamond film (∼271 eV) [21]). As it is known, the diamond Auger energy is the lowest among those of the carbon allotropic forms due to the absence of -electrons and wide bandgap ( E g = 5.1 eV), which radically shifts the spectrum high-energy edge to lower energies by ∼2· E g /2. ...
... At 0.5 J cm −2 , a deterioration in the diamond quality may be deduced from the reduced P0/A1 ratio, though the ability to discern two maxima on the lower energy side of the main minima at 268 eV suggests that the surface has not been entirely converted to amorphous or graphitic carbon forms. The new peak in the spectra with a minimum at 290 eV has been reported by the authors and others [22,39] on natural and CVD diamond. To originate from the carbon film, this peak must be a high energy satellite peak caused either by energy 'gain' from a plasmon, or from an Auger transition from a doubly ionized inner shell [25]. ...
Excimer laser projection patterning with an ArF (193 nm) source has been employed in the irradiation of thin diamond films. The effect of a number of process parameters including laser fluence and processing ambient on the quality of the etch product has been investigated; scanning electron microscopy shows that good control of etch quality may be achieved with excellent lateral reproduction of images down to 2 μm. Raman scattering and Auger electron spectroscopy of irradiated films have been correlated, and modifications in the diamond surface have been quantified according to processing parameters. Electrical tests on laser modified surfaces show that the reactivities of metals have a major role in the performance of contact metallizations on such a material. The viability of excimer laser etching of diamond as a manufacturing technique is considered.
... The deposits coated on wire after CVD treatment were identified by micro-Raman spectroscopy (wave number of argon laser beam: 488nm) and X-ray diffraction (XRD) analysis. 3. ...
Fine-grained and adherent diamond coating was obtained by the two-stage microwave plasma chemical vapor deposition (CVD) in the CO-H-2 system on a tungsten wire substrate mounted horizontally 2 mm up-ward on pyrophyllite susceptor. The susceptor was placed parallel to the irradiation direction of microwave. The nucleation density of diamond was found to increase with increasing the microwave power up to 1000 W. The first stage CVD conditions for fine-grained diamond coating on tungsten wire were determined as microwave power: 900 W, pressure: 2 kPa and CO concentration: 5 vol%. On the other hand, the second stage CVD conditions for higher growth rate of diamond him were determined as microwave power: 550 W, pressure: 4 kPa and CO concentration: 10 vol%. Homogeneous and adherent diamond coating with a thickness of 16 mu m was prepared by the two-stage CVD process for a total treatment time of 10 h (the first stage of 3h and the second stage of 7h) on tungsten wire of 1.0-mm diameter. A WC interlayer was formed during the CVD process.
Diamond fibres, ∼20-300 μm diameter and up to 150 μm long have been produced by chemical vapour deposition (CVD) on various metallic and ceramic core materials. Young's modulus values have been measured using several techniques including a resonance method and a tensile test. The composite fibres (core plus diamond coating) yield modulus values from ∼700 to 900 GPa, depending on the deposition conditions and diamond volume fraction. These values are substantially greater than those for existing continuous fibre reinforcements (e.g., SiC, modulus ∼400 GPa) used in current commercial metal matrix composites. Titanium matrix composites containing diamond fibres have been produced, and both individual fibres and fibre-reinforced composites have been cut and profiled using pulsed laser radiation. A substantial increase in the effective diamond deposition rate, defined as diamond mass deposited per unit time, and a corresponding reduction in diamond fibre composite cost are predicted for deposition on multiple fibre arrays.
The surface morphology, and chemical/structural modifications induced during chemical sputtering of ATJ graphite by low-energy (<200 eV/D) deuterium atomic and molecular ions are explored by Scanning Electron Microscopy (SEM), Raman and Auger Electron Spectroscopy (AES) diagnostics. At the lowest impact energies, the ion range may become less than the probe depth of Raman and AES spectroscopy diagnostics. We show that such diagnostics are still useful probes at these energies. As demonstration, we used these surface diagnostics to confirm the characteristic changes of surface texture, increased amorphization, enhanced surface reactivity to impurity species, and increased sp3 content that low-energy deuterium ion bombardment to steady-state chemical sputtering conditions produces. To put these studies into proper context, we also present new chemical sputtering yields for methane production of ATJ graphite at room temperature by impact of D2+ in the energy range 10–250 eV/D, and by impact of D+ and D3+ at 30 eV/D and 125 eV/D, obtained using a Quadrupole Mass Spectroscopy (QMS) approach. Below 100 eV/D, the methane production in ATJ graphite is larger than that in HOPG by a factor of ∼2. In the energy range 10–60 eV/D, the methane production yield is almost independent of energy and then decreases with increasing ion energies. The results are in good agreement with recent molecular dynamics simulations.
Diamond was coated onto wire substrates of various transition metals (Mo, W or Ti) of 0.5 mm diameter by the microwave plasma
CVD method from a gas mixture of the CO–H2 system. The CVD conditions for a uniform diamond coating were microwave power, 750–1100 W; total pressure, 2000 Pa; total
flow rate, 200 ml min-1; CO concentration, 5 vol%; treatment time, 5 h. The wire substrates were mounted vertically or horizontally
on a pyrophyllite susceptor, which was placed parallel to the irradiation direction of microwave power. Homogeneous and fine-grained
diamond film was prepared on the whole surface of horizontal W wire substrate with a wire height of 2 mm from the susceptor.
To obtain a dense diamond coating, the height has to be as low as possible in the plasma region, where the plasma density
is higher at lower substrate temperature. Low pressure and high microwave power were suited for fine-grained coating. Diamond
deposition rate was found to be more dependent on pressure than substrate temperature. As the pressure increased, a glassy
carbon film was formed instead of diamond.
Diamond thin films were grown by microwave plasma and hot filament chemical vapor deposition (MPCVD and HFCVD, respectively) techniques. Films were systematically characterized by x-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy (SEM), and Auger electron spectroscopy (AES). Although the results obtained using various characterization techniques are broadly similar, there are however subtle differences. For instance, Raman spectra show a sharp peak at ≃ 1332 cm-1 corresponding to natural diamond in both types of films. The intensity and the position of the non-diamond band in the two sets of films differ. While the maxima of the non-diamond band in HFCVD film lies at 1450 cm-1, in MPCVD film it occurs at 1525 cm-1. Also the values of FWHM in HFCVD film (≃ 7.5 cm-1) are smaller than the MPCVD films (≃ 9.5 cm-1). This may indicate that the concentration of non-diamond carbon impurities on the grain boundaries of HFCVD films are really small. SEM results on the other hand indicate that the grain size of the MPCVD films is larger than HFCVD films. AES was performed in a survey scan (beam size ∼10 μm × 8 μm) and high resolution (beam size ≃ 0.2 μm) mode with an initial aim to investigate the surface characteristics and environment of carbon atoms of the diamond films. In the survey scan, the spectra show a line shape typical of CVD diamond films. Anomalous results were obtained when the AES was performed on (100) and (111) facets in high resolution mode. This may be explained in terms of the surface reconstruction taking place due to hydrogen desorption via core-hole Auger decay process. Auger depth profiles were- - also obtained on the facets which reveal that Si, O, and N are the dominant impurities. The impurity content of HFCVD films is observed to be lower by a factor of 2 as compared to MPCVD films. © 1998 American Vacuum Society.
An improved non-contact strain measurement technique was used during tensile testing to measure the fracture strength, failure strain and Young's modulus of diamond-coated fibres produced by hot-filament chemical vapour deposition (HFCVD).Diamond coated tungsten fibres/wires were produced under a range of deposition conditions. Fibre fracture strengths were in the range 207–1189 MPa, corresponding to diamond strengths of 257–1658 MPa. Fibre strength was strongly inversely related to coating thickness. Examination of the fracture surfaces indicated that two different modes of failure had been undergone.The fibre Young's modulus was in the range 486–814 GPa. Calculation of the corresponding diamond coating modulus gave values of 559–1054 GPa.
