Diamond Phase Content Research Articles

Influences of grain size and microstructure on optical properties of microcrystalline diamond films**Project supported by the Key Project of the National Natural Science Foundation of China (Grant No. U1809210), the National Natural Science Foundation of China (Grant Nos. 50972129 and 50602039), the International Science Technology Cooperation Program of China (Grant No. 2014DFR51160), the National Key Research and Development Program of

Microcrystalline diamond (MCD) films with different grain sizes ranging from 160 nm to 2200 nm are prepared by using a hot filament chemical vapor deposition (HFCVD) system, and the influences of grain size and structural features on optical properties are investigated. The results show that the film with grain size in a range of 160 nm–310 nm exhibits a higher refractive index in a range of (2.77–2.92). With grain size increasing to 620±300 nm, the refractive index shows a value between 2.39 and 2.47, approaching to that of natural diamond (2.37–2.55), and a lower extinction coefficient value between 0.08 and 0.77. When the grain size increases to 2200 nm, the value of refractive index increases to a value between 2.66 and 2.81, and the extinction coefficient increases to a value in a range of 0.22–1.28. Visible Raman spectroscopy measurements show that all samples have distinct diamond peaks located in a range of 1331 cm−1–1333 cm−1, the content of diamond phase increases gradually as grain size increases, and the amount of trans-polyacetylene (TPA) content decreases. Meanwhile, the sp2 carbon clusters content and its full-width-at-half-maximum (FWHM) value are significantly reduced in MCD film with a grain size of 620 nm, which is beneficial to the improvement of the optical properties of the films.

Microstructural and electrochemical properties of sulfur ion implanted nanocrystalline diamond films

Nanocrystalline diamond (NCD) films have a composite structure composed of diamond grains and amorphous carbon grain boundaries. Compared with microcrystalline diamond (MCD) films, the NCD film grain boundaries are rich in a large number of π bonds, thus providing conductive channels. Its conductivity is 3−7 orders of magnitude higher than that of MCD, and the surface of NCD film is uniform and dense, and the roughness is lower, so the NCD film is a promising electrode material. In our previous study, microwave plasma chemical vapor deposition was successfully used to prepare n-type sulfur-doped diamond films with good electrical properties. However, the electrochemical properties of sulfur-doped nanocrystalline diamond films have not been studied till now. In the present work, the nanocrystalline diamond films are prepared by the hot-wire chemical vapor deposition. The films are subjected to ion implantation and vacuum annealing. The effects of annealing temperature on the microstructure and electrochemical properties of the films are investigated. The results show that the sulfur ion implantation is beneficial to the improvement of the electrochemical reversibility of the film. When annealed at 800 °C and below, the amorphous carbon phase at the grain boundary in the film gradually changes into the trans-acetylene phase, resulting in a gradual deterioration of electrochemical performance. When the annealing temperature rises to 900 °C, Raman spectrum and TEM results show that the film has more diamond phase content and better lattice quality, and the trans-polyacetylene in the grain boundary is cracked; XPS results indicate that the CO bond at this time, C=O bond, and π—π* content increase significantly; Hall test shows that the film mobility and carrier concentration are significantly higher than those of unannealed film. The redox peak in the electrolyte is highly symmetrical, the peak potential difference is reduced to 0.20 V, the electrochemical active area is increased to 0.64 mC/cm<sup>2</sup>, and the electrochemical reversibility is much better thanthose of samples annealed at 600 °C, 700 °C, and 800 °C, respectively.

Dependence of the Diamond Phase Content in Condensed Detonation Carbon on Trinitrotoluene Concentration in the Explosive Mixture Trinitrotoluene/Diethanolamine Dinitrate

Dependence of the Diamond Phase Content in Condensed Detonation Carbon on Trinitrotoluene Concentration in the Explosive Mixture Trinitrotoluene/Diethanolamine Dinitrate

Dependence of the Diamond Phase Content in Condensed Detonation Carbon on Trinitrotoluene Concentration in the Explosive Mixture Trinitrotoluene/Diethanolamine Dinitrate

Dependence of the Diamond Phase Content in Condensed Detonation Carbon on Trinitrotoluene Concentration in the Explosive Mixture Trinitrotoluene/Diethanolamine Dinitrate

Study of the Mechanical Characteristics of Single-Layer and Multilayer Nanostructures Based on Carbon and Fluorocarbon Coatings

The results of studying the nanohardness and Young’s modulus of single-layer and multilayer nanostructured barrier layers prepared by methods of ion-plasma technology on the basis of carbon and fluorocarbon coatings, which are formed on the surface of polystyrene in the region of transitional-process modes (transition from etching to film deposition), are described. Fluorocarbon films formed in the region of transitional-process modes exhibit an antiadhesive effect against microorganisms and can be used to prevent the biodegradation of polymers. After exposure to CF4 ions and the deposition of a single-layer carbon or fluorocarbon coating and a multilayer coating in the region of transitional-process modes, the Young’s modulus values are significantly (2–3 times) higher than the values of pure polystyrene. For the samples with a sublayer deposited at an accelerating voltage between the anode and the cathode in an II-4-0.15 ion source of 3 kV, the nanohardness increases by 1.5 times; at an accelerating voltage of 2 kV, the nanohardness decreases. This finding can be attributed to the fact that, at an accelerating voltage of 2 kV, the diamond phase content in the deposited film decreases.

Novel Diamond Films Synthesis Strategy: Methanol and Argon Atmosphere by Microwave Plasma CVD Method Without Hydrogen.

Diamond thin films are grown on silicon substrates by only using methanol and argon mixtures in microwave plasma chemical vapor deposition (MPCVD) reactor. It is worth mentioning that the novel strategy makes the synthesis reaction works smoothly without hydrogen atmosphere, and the substrates temperature is only 500 °C. The evidence of surface morphology and thickness under different time is obtained by characterizing the samples using scanning electron microscopy (SEM). X-ray diffractometer (XRD) spectrum reveals that the preferential orientation of (111) plane sample is obtained. The Raman spectra indicate that the dominant component of all the samples is a diamond. Moreover, the diamond phase content of the targeted films was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS) method, and the surface roughness of diamond films was investigated by atomic force microscope (AFM). Meanwhile, the possible synthesis mechanism of the diamond films in methanol- and argon-mixed atmosphere was discussed.

Optimization of Growth Parameters for Diamond Films Grown by MPCVD Using Response Surface Methodology

Diamond films were synthesized by microwave plasma chemical vapor deposition under different deposition parameters. Response surface methodology was adopted to guide the optimization of synthesis parameters including the substrate temperature (716–884 \({^{\circ}{\rm C})}\), gas pressure (4.32–7.68 kPa), and volume concentration of methane to hydrogen (1.3–4.7 %) for deposition of the films. A 5-level-3-factor central composite design was employed to evaluate effects of the deposition parameters on the response (growth rate and pure index). The significant level of both the main effects and the interaction is investigated by analysis of variance. With its assistance, the growth quality of the obtained samples was improved dramatically. The structure, surface morphology and growth rate of films were characterized by X-ray diffractometer and scanning electron microscopy. The diamond phase content of films was investigated using Raman spectroscopy and X-ray photoelectron spectroscopy. The optimum substrate temperature, gas pressure, and volume concentration of methane to hydrogen were found to be 837 \({^{\circ}}\)C, 6.95 kPa and 2 %, respectively. Under this experimental condition, the growth rate and pure index of diamond films were 0.378 \({\mu}\)m/h and 4.092, which are quite good correlation with value (0.383 \({\mu}\)m/h and 4.182) predicted by the model. The diamond phase content of the films is 89.5 %.

Synergetic surface modification effect of argon and oxygen for diamond films by MPCVD

Abstract Diamond films were synthesized in a CH4-H2 system with good surface quality by adjusting the additive amount of argon and oxygen gas. The diamond phase content and surface roughness of samples are 86.1% and 81.5 nm, respectively. The results indicate that only Ar addition will decrease the purity of diamond films, whereas Ar-O2 mixed gas can further increase the diamond phase content. It is worth noting that the content of diamond phase has no significant increase when O2 flow exceed 1 sccm. The surface roughness reduced from 199.8 to 81.5 nm by the addition of 14 sccm Ar and 1 sccm O2, and the surface quality will be deteriorated in case of further increasing O2 or decreasing Ar concentration. Meanwhile, the growth rate under different conditions and the synergetic surface modification effect of Ar-O2 mixed gas for diamond films growth process were discussed.

Evaluation of resistance of diamond-like carbon coating to the corpuscular radiation in outer space conditions

The purpose of this work was to research the resistance of thin coatings to the effects of corpuscular radiation, as well as evaluation speed etching of diamond-like films with different content of diamond phase. There were two samples of monocrystalline silicon with DLC coating. To evaluate the resistance, two groups of grooves were etched on each sample. The depth was then measured to calculate a relative etching ratio of DLC coating. The resistance was determined to be four times that of silicon.

The microstructural and electrochemical properties of oxygen ion implanted nanocrystalline diamond films

The nanocrystalline diamond (NCD) films are implanted by oxygen ions with a dose of 1×1012 cm-2 and subsequently annealed at 700, 800, 900 and 1000 ℃, respectively. The microstructure and electrochemical properties of these NCD films are investigated systematically and the results show that the potential windows of the unannealed sample (O120) and 1000 ℃ annealed sample (O121000) increase up to 4.6 V and 3.61 V, respectively. The mass transfer efficiencies of the two samples are also better, indicating that the oxygen ion implantation and 1000 ℃ annealing can improve the mass transfer efficiency of NCD film. The results of infrared spectrum measurements show that there are no hydrogen atoms that are terminated to the surfaces of samples O120 and O121000, while hydrogen atoms terminate to the surfaces of the other samples. It is indicated that oxygen ion implantation and 1000 ℃ annealing can damage hydrogen terminations in the surface, which improves the electrochemical performances of NCD films. Raman spectrum measurements suggest that high content of diamond phase, small internal stress and more disordered amorphous carbon can improve the electrochemical properties of NCD films. When the number or size of sp2 carbon clusters in amorphous carbon grain boundaries decreases, the electrochemical properties of NCD films become better.

Effects of annealing temperature on the microstructure and p-type conduction of B-doped nanocrystalline diamond films

Annealing of different temperatures was performed on boron-doped nanocrystalline diamond (BDND) films synthesized by hot filament chemical vapor deposition (HFCVD). Effects of annealing temperature on the microstructural and electrical properties of BDND films were systematically investigated. The Hall-effect results show that smaller resistivity and Hall mobility values as well as higher carrier concentration exist in the 5000 ppm boron-doped nanocrystalline diamond film (NHB) as compared with those in 500 ppm boron-doped nanocrystalline diamond film (NLB). After 1000 ℃ annealing, the Hall mobility of NLB and NHB samples were 53.3 and 39.3 cm2·V-1·s-1, respectively, indicating that annealing increases the Hall mobility and decreases the resistivity of the films. HRTEM, UV, and visible Raman spectroscopic results show that the content of diamond phase in NLB samples is larger than that in NHB samples because higher B-doping concentration results in a greater lattice distortion. After 1000 ℃ annealing, the amount of nano-diamond phase of NLB and NHB samples both increase, indicating that a part of the amorphous carbon transforms into the diamond phase. This provides an opportunity for boron atoms located at the grain boundaries to diffuse into the nano-diamond grains, which increases the concentration of boron in the nano-diamond grains and improves the conductivity of nanocrystalline diamond grains. It is observed that 1000 ℃ annealing treatment is beneficial for lattice perfection of BDND films and reduction of internal stress caused by doping, so that the electrical properties of BDND films are improved. Visible Raman spectra show that the trans-polyacetylene (TPA) peak (1140 cm-1) disappears after 1000 ℃ annealing, which improves the electrical properties of BDND films. It is suggested that the larger the diamond phase content, the better lattice perfection and the less the TPA amount in the annealed BDND samples that prefer to improve the electrical properties of BDND films.

Effects of annealing time on the microstructural and electrochemical properties of B-doped nanocrystalline diamond films

The effects of annealing time under 1000 ℃ on the microstructural and the electrochemical properties of boron-doped nanocrystalline diamond (BDND) films are investigated by HRTEM, UV and visible Raman spectroscopy, and cyclic voltammetry measurements. The results show that the size of nano-diamond grain in the film decreases with annealing time increasing. When the annealing time is 0.5 h, the grain size decreases from about 15 nm in the unannealed sample to about 8 nm and the content of diamond phase increases. When the annealing time increases to 2.0 h, the diamond grain size decreases to 2-3 nm, and the content of diamond phase decreases with the grain boundary increasing. In the case of annealing time of 2.5 h, the grain size of nano-diamond and the content of diamond phase increase slightly. The variations of nano-diamond grain size and the content of diamond phase indicate that the transformation between the diamond phase and the amorphous carbon occurs under the annealing with different times. The visible Raman spectra show that the G-peak position and the ID/IG value exhibit similar variations with annealing time increasing, revealing that the ordering of the amorphous graphite phase is improved when sp2 carbon cluster increases in number or size. The reactions on the electrode surface are quasi-reversible when the annealing times are 0.5, 1.0, 1.5 and 2.0 h. On the contrary, the reactions are irreversible when the sample is unannealed or annealed for 2.5 h. It is observed that the annealing treatment is beneficial to the improvement of the electrode mass transfer efficiency of BDND film. When the annealing time is 0.5 h, the electrode mass transfer efficiency as well as the ability of catalytic oxidation of BDND film is best. The results suggest that the smaller size of nano-diamond grain, the higher content of diamond phase and the uniform distribution of the nanocrystalline diamond grains are conducible to the improvement of the reaction reversibility on the electrode surface and the ability of catalytic oxidation of BDND films.

Deposition of Amorphous Diamond Films on Different Substrates by Electrolysis of Methanol Solution

Amorphous diamond films were deposited on both (100) silicon and 316L stainless steel substrates at atmospheric pressure and low temperature (60°C) with a direct current pulsed power supply using methanol/additive solution as electrolyte. The morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM) and Raman spectroscopy. The friction and wear behavior of the films were examined on the CERT test system. The SEM observations showed that the films consisted of fine and compact ball-like grains with about 300nm in diameter. Raman spectroscopy analysis confirmed the diamond structure by the presence of strong peaks at 1333cm-1 for both substrates. The friction coefficient of the films deposited on both substrates against WC ball was about 0.10 at ambient conditions. The active additive could play an important role not only in improving adhesive strength between the films and substrates, but also in increasing relative content of diamond phase in the films.

Investigation of diamond-like-carbon films prepared by unbalanced magnetron sputtering

Using unbalanced magnetron sputtering method, smooth, dense and uniform diamond like carbon films (DLC) with high diamond phase content are deposited.Based on testing and analysis of deposition mechanism, we conclude that with smaller s puttering clusters and higher collision frequency between the sputtering cluster and environment molecules, and more suitable momentum of the sputtering cluste r impacting on the substrate, higher content of diamond phase in the film will result. Scanning electron micrograph shows that there are no obvious grains in this film. The micro-hardness is about 11 GPa, bulk elastic modulus is about 120 GPa as tested by nano-indentation. The optical transmittance is about 89%, ref raction coefficient is 1.952, and the deposition rate is 0.724μm/h as calculate d from the FTIR spectra.

Raman scattering, AFM and nanoindentation characterisation of diamond films obtained by hot filament CVD

In this work, structure and mechanical properties of diamond films fabricated by HFCVD on silicon substrates with nanodiamond seeding were investigated. Raman spectroscopy was used to characterise the diamond phase content, crystalline quality and source of stresses in these films. Topography, hardness and Young's modulus were studied by scanning force microscopy (SFM) and nanoindentation methods. It has been ascertained that for the diamond films grown on silicon substrates with nanodiamond seeding hardness and crystalline quality is higher than for films on scratched silicon. The diamond films demonstrate Raman upshift with respect to natural diamond, indicating presence of internal compressive stress. It was shown that various types of impurities and defects induce compressive stresses in the diamond grains.

Growth of diamond films on crystalline silicon by hot-filament chemical vapor deposition

The effect of hot-filament chemical vapor deposition conditions on the phase composition of diamond films grown on a silicon substrate was studied. The growth conditions providing the highest content of diamond phase at a growth rate of about 1 µm/h were ascertained.