Surface Morphology Of Diamond Films Research Articles

Effects of Substrate Bias on the Diamond Nanostructure by Reactive Ion Etching

Dense and uniform diamond nanocone arrays on titanium substrate were constructed by using bias-assisted reactive ion etching (RIE) of diamond films in a microwave plasma chemical vapor deposition (MPCVD) system. A hydrogen/argon mixture was employed as work gas with ratio of 3/1. The formation of nanocone structure was generated the lengthways physical bombardment/sputtering by argon ions, and selective chemical reaction of graphite and disordered carbons by hydrogen atoms and ions. The structure, size, and density depended on the substrate bias. The surface morphology of diamond film and nanostructures were characterized by field emission scanning electron microscope (FESME), and the composition of diamond film and nanostructures were characterized by Raman spectra. The Stopping and Range of Trons in Matter (SRIM) software was used to simulate the bombardment effect of the diamond film on different Ar+ ion incident angles during the etching process. The experimental results showed substrate bias at −180 V and −210 V was beneficial to the formation of high density, small size and sharp nanocones, meanwhile larger bias contributed to the formation of large size nanocones. Besides, as-prepared nanocones still maintained significant diamond phase.

Rapid grinding CVD diamond films using corundum grinding wheels containing iron

An efficient grinding wheel has been designed for grinding diamond film which is prepared by chemical vapor deposition. The grinding wheel ((Cu-Sn+Al2O3)+Fe) was prepared by adding iron to metal-based corundum grinding wheel. It had been demonstrated that the grinding wheel exhibited the highest material removal rate compared with metal grinding wheel (e.g. SUS 304 and cast iron) and the material removal rate could reach 5.57–70.32μmh−1 at the grinding speed of 200–500rpm. By means of scanning electron microscope, transmission electron microscope, X-ray diffraction and Raman spectroscopy, the surface morphology of diamond film in different grinding speeds and the grinding mechanism were studied. The results showed that the material removal mechanism was mainly the chemical reaction between diamond and iron and graphitization of diamond with the iron as the catalyst during grinding.

Effects of Two-Step DC Electrochemical Pretreatment of Fine Grinding WC-Co Tool Surface on Morphology and Quality of Diamond Coatings

In the present investigation, diamond coating was deposited on fine grinding cemented carbide substrate by direct current arc discharge chemical vapor deposition. The effect of electrolytic etching time in the two-step electrochemical pretreatment process (firstly using electrolytic etching, and then using acid etching) on morphology and quality of the diamond coating were systemically studied. The surface morphology feature and quality of diamond coatings were characterized by means of Scanning Electron Microscope (SEM), laser Raman spectrometer respectively. The results showed that the electrolytic etching duration has distinctly effect on the quality and crystal features such as morphology, crystal type and grain size of diamond coating. It showed that as electrolytic current is direct current 3A, electrolytic etching time altering from 0.5 min to 7.5min, the surface morphology of diamond films gradually transition from microcrystalline cubic-octahedron to cauliflower type nanocluster, and further increase the electrolytic etching time, will lead to several negative effects on the quality and nucleation of the coatings which is not only retard the diamond nucleation, but also promote the formation of graphite.

Influence of Surface Morphology of Diamond Films on their Frictional Behaviors in Dry and Water Environments

The influence of surface morphology of diamond films on their friction behaviors was investigated under both ambient air and water environments. The diamond films with three different surface morphologies were deposited on the Co-cemented tungsten carbide (WC-6wt%Co) substrate using hot filament chemical vapor deposition (HFCVD) method and their frictional behavior were studied on a ball-on-plate type reciprocating friction tester, where the ball-bearing steel was used as the counterface materials. The coefficient of friction (COF) of diamond films showed strong surface morphology dependence, those samples with smaller diamond grain size and smoother surface finish represented lower COF in both dry and water lubricating conditions. Water lubricating was significantly favor to decrease the COF of diamond films, which might mainly due to the lubricating effect of physisorbed water layer formed on the sliding interface. In addition, the transferred materials layer adhered on the worn surface of diamond films were supposed to be another factor that was beneficial for reducing the COF.

Effect of Boron Concentration on Adhesion and Cutting Performance of Diamond-Coated Cemented Carbide Tools

Diamond thin films doped with various boron concentrations were grown on WC-Co cemented carbide tools by hot-filament-assisted chemical vapor deposition (HFCVD). The trimethyl borate dissolved in acetone solution was used as the boron resource (B/C=0%, 0.1%, 0.3%, 0.5%). The surface morphology of diamond films with different boron contents was investigated by Scanning electron microscopy, the adhesive strength was calculated by means of indentation test under a load of 1500N. A real cutting performance was carried out on Al metal matrix composites material (20vol%SiC, 15μm), and the insert flank wear was examined by measuring the scars that appeared on the cutting edge with tool microscope. The research results shown the surface morphology and structure of the diamond films changed owing to boron doping. As the doping levels increased, the average grain size of the films decreased from 10 to 2μm. A significant improvement in adhesion and cutting performance were observed as the boron contents increased from 0% to 0.5%. The adhesion and cutting performance were best when the boron concentration was 0.3%. Adequate boron can effectively suppress the cobalt diffusion to the substrate surface and avoid the catalytic effect of cobalt at the high temperature. It is of great significance for improvement of the adhesive strength and cutting performance of diamond-coated tools using above method.

Assessment of the Surface Morphology of Diamond Film Based on Fractal

The surface morphology of film material directly affects its physical performance. It is of great significance for finding out its prospective physical performance to characterize the surface morphology of film material. It is hard to characterize them with some conventional methods. The surface morphology of film material was described from the fractal point of view, and the dimension was correlated with the resistivity of material. The [100]-orientated diamond film was primarily investigated. The results show that the greater the crystal grain is, the more uniform and regular the orientation is; and the more compact the arrangement is, the greater the fractal box dimension is. Moreover, when fractal box dimensions were within a certain range approximately from 2.92 to 2.97, it presents positively correlative relation with the logarithm of resistivity, Log(ρ), which resembles the Logistic curve. However, when the other dimensions are beyond the range mentioned above, resistivity doesn’t change with the increase in dimensions of fractal. This study will conduce to illustrating the relationship between the structure of crystal exemplified by arrangement and physical performance as well as material preparation.

Evaluation research of polishing methods for large area diamond films produced by chemical vapor deposition

The current study compared several polishing techniques of chemical vapor deposition (CVD) diamond films. Although research on various diamond polishing techniques has been carried for years, some issues still need to be examined in order to facilitate application on large areas in a cost-efficient manner. In the present work, microwave plasma enhanced chemical vapor deposition (CVD) was used to obtain diamond films with full width half magnitude (FWHM) less than 10 wavenumbers at 1332 cm − 1 Raman peak. The diamond films were processed through mechanical polishing, chemical-assisted mechanical polishing, thermo-chemical polishing, excimer laser ablation, and catalytic reaction assisted grinding. A profilometer, an atomic force microscope, and a scanning electron microscope have been used to evaluate the surface morphology of diamond films before and after polishing. The results obtained by using the above mentioned techniques were analyzed and compared.

Effects of substrate bias on the structural and field emission properties of diamond films

The effect of electron bombardment on modification of the structural property and the surface morphology of diamond films, and consequently the field emission properties have been investigated by introducing positive substrate bias. When increasing the bias voltage, the structural properties of diamond films are significantly deteriorated together with the increase of nondiamond carbon component and the surface morphologies of the films lost their unique facet shape. The reason for the increase of nondiamond carbon content is described in terms of both the increase of substrate temperature and the excessive generation of CHn radicals. The field emission properties of diamond films were substantially improved with increasing bias voltage. Enhancement of field emission property for the films prepared by increasing bias voltage and/or methane concentration has been discussed by correlating between the substrate–diamond interface property and the slope of the Fowler–Nordheim plot.

Field emission characteristic of diamond films grown by electron assisted chemical vapor deposition

By introducing positive substrate bias, ranging from 0 to 200 V, to the substrate during the growing procedure of diamond at 1, 2, and 3% CH4 concentration, we have investigated the effect of electron bombardment on modification of the structural property and the surface morphology of diamond films, and consequently the field emission properties. When increasing the bias voltage for each CH4 concentration, the structural properties of diamond films are significantly deteriorated together while the non-diamond carbon component increased and the surface morphologies of the films lost their unique facet shape. The reason for the deterioration of the structural property was attributed to both the increase of substrate temperature and the excessive generation of CHn radicals. Especially for the films deposited at 2% CH4 concentration under 100 V, it was observed that their morphological and structural characteristics approached those of graphitic carbon nature. The field emission properties of diamond films were substantially improved with increasing the CH4 concentration and with the application of bias voltage for each CH4 concentration. In order to investigate the correlation between the enhancement of field emission properties and the emission sites, we have examined the spatial distribution of the emission sites. From this result, a possible emission mechanism is discussed.

Synthesis of diamond in high power-density microwave methane/hydrogen/oxygen plasmas at elevated substrate temperatures

Resumen Effects of elevated substrate temperatures and oxygen additive on the chemical vapor deposition of diamond are presented. High power-density microwave plasmas in a high concentration of methane diluted by hydrogen led to high diamond growth rates at elevated substrate temperatures up to around 1450°C. When methane and hydrogen were the only reactant gases and the substrate temperature was higher than 1450°C, graphitic deposits started to show up. With the addition of a small amount of oxygen (less than 2%), diamond films deposited at substrate temperatures higher than 1450°C at 30 μm h −1 were achieved. Diamond deposition at substrate temperatures exceeding 1600°C was achieved on molybdenum substrates. At such high temperatures, diamond grows well but the nucleation density was low. Raman spectra and surface morphologies of diamond films are correlated with the growth conditions.

Influence of oxygen and nitrogen on the growth of hot-filament chemical vapor deposited diamond films

The effect of incorporating oxygen and nitrogen into the feed gases on the texture and surface morphology of diamond film synthesized by hot filament chemical vapor deposition (HFCVD) is investigated. The reactant gas composition is determined by the gas flow rates. At a constant flow rate of hydrogen (33sccm) and methane (0.68sccm), the oxygen and nitrogen were varied in the O/(O + C) ratio from 0.05 to 0.43 and in the N/(N + C) ratio from 0.15 to 0.60. The films were grown under a constant pressure (20Torr) and a constant substrate temperature (800°C). Clearly nitrogen in the reactant gases has a distinct tendency to promote the 〈100〉 texture and the corresponding {100} morphology, whereas oxygen promotes the development of 〈111〉 texture and {111} morphology. According to the Wulff theorem (Γ=d100/d111=γ100/γ111) and the evolutionary selection of crystallites and the surface configurations of diamond, the results reveal that during growth nitrogen plays a critical role in activating the CD–H surface site and consequently increases the surface free energy γ111, of the {111} surface. In contrast, oxygen activates the CDH2 surface site and increases the surface free energy γ100, of the{100} surface. These results indicate that the texture and the surface morphology of polycrystalline diamond film can be completely controlled by the reactant gas composition.

Variations of morphology and electrical property of diamond with doping using diborane in a methane–hydrogen gas mixture

The shape of isolated diamond particles and the surface morphology of diamond films were investigated at various boron concentrations. The diamond particles and films were deposited using a microwave plasma-assisted chemical vapor deposition method at 70 Torr with various diborane concentrations from 0 to 4000 ppm in hydrogen–2% methane gas. The shape of isolated particle changed from cubo-octahedron to octahedron via truncated-octahedron as the diborane concentration increased. The growth rate decreased rapidly and then remained constant with further increasing diborane concentration. The changes of particle shape and growth rate were explained by the charge-polarity model of cursor gas, and by the relative growth rate of (100) and (111) facets, which were controlled by the boron concentration. The surface morphology of diamond films varied in accordance with the change of the shape of the diamond particles. The resistivity of the diamond film decreased owing to the increase of carrier concentration as the diborane concentration increased to 500 ppm, below which the shape of isolated diamond particles was cubo-octahedral.

Change in surface morphology of diamond films deposited by DC plasma glow discharge CVD

The influence of the deposition conditions on the morphology of two diamond samples prepared by DC plasma glow discharge CVD has been investigated. A structural change has been observed from a 〈110〉 textured morphology, to the morphology of randomly oriented grains with a heavily disturbed crystalline structure, by decreasing the substrate temperature from 1100 to 950°C. Features of the different morphologies have been studied by SEM and related to the results of Raman spectroscopy and X-ray diffraction. The growth side of the first sample presents cubo-ochtaedral grains with low mutual misorientation while the growth side of the second sample is characterised by ball-shaped structures due to an high density of renucleation on the growing planes, separated by deep interdomain regions. The size of the grains forming the rounded structures decreases gradually towards the bottom of these regions. The poorer crystalline quality of this sample is related to its Raman spectrum, showing an higher luminescence and the presence of graphite-like phases all over the growth surface. Moreover an higher density of defects is evidenced by the higher broadening of the Raman diamond line and of the Bragg diffraction peaks with respect to the textured sample. Analogous results have been reported for a microwave CVD reactor. In this work we confirm the hypothesis that this structural change does not depend on the particular CVD method which are likely to provide the same film quality and morphology at different plasma conditions if the activation of the reactant gases and the surface mobility are in the same range of values.

A study on surface morphologies of diamond films

The surface morphologies of polycrystalline diamond films deposited by the chemical vapor deposition (CVD) technique usually exhibit regular changes with increasing substrate temperature from ball-like amorphous carbon-hydrogen to polycrystalline diamond with predominant facets {100}, followed by {111} facet formation with finally, formation of microcrystalline graphite-rich deposits. We have calculated the temperature dependence of surface energies of the chemical vapor deposited diamond crystals during the preparation process using a model in which a fraction of carbon dangling bonds on the growth surface is saturated by hydrogen. The results can be used to interpret the regular changes of the surface morphologies of CVD diamond films.

Scanning tunneling microscopy of the electronic structure of chemical vapor deposited diamond films

Scanning tunneling microscopy has been used to characterize the electronic structure and surface morphology of diamond films grown using the hot filament and microwave plasma chemical vapor deposition techniques. We observe a significant difference between the current-voltage (I-V) curves for the two types of films. The I-V curves for the hot-filament grown films are characterized by a well-defined zero-current region from which a surface band gap of 4.1 eV is measured. The I-V curves for the microwave plasma grown films exhibit a rectifying behavior which can be modeled by surface band bending. We compare the surface density of states obtained from the I-V curves with those obtained from x-ray photoelectron and appearance potential spectroscopies.

Characteristics of thin film growth in the synthesis of diamond by chemical vapour deposition and application of the thin film synthesis technology for tools

Diamond films were synthesized under various reaction conditions by hot-filament thermal chemical vapour deposition (CVD). Under reaction conditions of a low total pressure, or a high CH 4 concentration, or a long distance between the filament and the substrate, the surface morphologies of diamond films are of a very-fine-grained coagulated spherical structure. In these cases, strong peaks of amorphous carbon phases in laser Raman spectra were detected. From reflection high energy electron diffraction results and X-ray diffraction analysis, it was concluded that an amorphous carbon phase exists on the surfaces and also between the grain boundaries of diamond polycrystals. Cutting performance tests were carried out to investigate the possibility of utilizing CVD diamond films as a wear-resistant coating for cutting tools. It was also concluded that the CVD diamond coating on cemented-carbide inserts is an effective means of prolonging the life of the insert for turning non-ferrous metals, and, in particular, aluminium alloys and semisintered ceramics.