Growth kinetics of diamond film with bias enhanced nucleation and H 2/CH 4/Ar mixture in a hot-filament chemical vapor deposition system (original) (raw)
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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2001
Micro-crystalline diamond films and nano-carbon structures in the form of wires have been grown by the introduction of argon at very high concentrations ͑60%-87.5% vol Ar͒ into the feed mixture ͑ethanol and hydrogen͒ of a hot-filament chemical vapor deposition reactor. The argon, in addition to acting as an inert diluent, also modified the kinetics of the carbon deposition process; its presence apparently minimized the deposition of intergranular hydrogenated species, induced an increase in the number of flaws between the diamond grains, increased the porosity of the films, and formed new carbon structures. Well-faceted diamond films, diamond-like carbon ͑DLC͒ balls, spongy-like wires, and multilayer structures were observed at different concentrations of Ar. Raman spectroscopy of the deposited material showed that structures of high quality diamond ͑60%-65% vol Ar͒ and carbon structures related to DLC, fullerenes and carbon nanotubes, may be deposited by this process.
Diamond and Related Materials, 2005
A study of the evolution of morphology of diamond films grown as a function of N 2 gas additions to the CH 4 +H 2 precursor in an HF-CVD system is presented. With the increase of admixture of N 2 fraction, in contrast to earlier studies, the morphology was observed first to gradually change from {111}-faceted crystallites texture to that of an intermediate cubo-octahedral crystallite texture and then gradually but finally to transform completely into that of {100}-faceted crystallites. The threshold nitrogen concentration, [N 2 ] thr , required to bring about the said transition in morphology was much larger than it was reported previously. Moreover, the morphology transition required a larger [N 2 ] thr when a large fraction of methane was employed. Further additions of nitrogen, that just exceeded the [N 2 ] thr , resulted in growth of films containing slightly bigger {100}-multi-layered grains or isolated planar {100}-platelets. For extremely large nitrogen additions, the growth of nanocrystalline or amorphous carbon films was observed. The N 2 additions more than 50 vol.% did not yield any deposition. Raman scattering and photoluminescence measurements were used respectively for characterizing the quality and nitrogen doping in the films. These results are attributed to the possible catalytic role of atomic nitrogen at the growing surface.
Effect of argon and substrate bias on diamond thin film surface morphology
Vacuum, 2007
Nanocrystalline materials are of high interest, because mechanical and physical properties of such materials are different from those or coarse-grained type. Continuous and smooth nanocrystalline diamond (NCD) thin films were successfully grown on mirror polished silicon substrates, using double bias plasma-enhanced hot filament chemical vapour deposition technique. A gas mixture of Ar:CH 4 :H 2 and CH 4 :H 2 was used as the precursor gas. The effect of the gas composition, flow rate and substrate bias during deposition on diamond crystallite size was investigated. Changing the growth parameters facilitates control of grain size of polycrystalline diamond thin films from microcrystalline to nanocrystalline. The structure of fine-grained NCD films has been studied with scanning electron microscopy and Raman spectroscopy. r
NUCLEATION AND GROWTH OF DIAMOND IN HOT FILAMENT ASSISTED CHEMICAL VAPOR-DEPOSITION
Journal of Materials Science Letters, 1991
Increasing interest in the low pressure, gas-phase growth of diamond has arisen due to the combination of its exceptional chemical, mechanical, elec-tron{c, thermal, and optical properties . Polycrystalline diamond films have been successfully grown by various forms of chemical vapour deposition (CVD) methods [7][8]; and characterization of these films has been discussed in several review articles [7][8]. One of the many aspects that has to be understood concerns the kinetics of nucleation and growth of diamond on non-diamond substrates 8]. The relative rates of these nucleation and growth processes affect the crystalline size and the morphology of t])e resulting film. We and others have studied the effect of process variables such as gas composition [9], temperature [10], and pressure [11] on the morphology and grain size of the deposited films. However, there have been relatively few studies on the growth kinetics of diamond from the vapour phase. In one such study, the authors used a microbalance to monitor the change in the weight of diamond growth on diamond powder as a function of time [12][13][14].
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2014
The effect of substrate temperature upon the growth rate and the properties of diamond thin films grown with different grains sizes is explored. An argon-free and argon-rich gas mixture of methane and hydrogen is used in a hot filament chemical vapor deposition reactor. Characterization of the films is accomplished by scanning electron microscopy, Raman spectroscopy and high-resolution x-ray diffraction. Arrhenius plots of the mass gain, thickness growth, and renucleation rate as a function of the substrate temperature are used to obtain the values of the activation energies. An extensive comparison of the activation energy values obtained in this study with those found in the literature suggests that there are distinct common trends for microcrystalline and ballaslike diamond growth. Besides the activation energy values, the morphology, crystallite size, sp 2 quantification, mass gain, thickness growth, and renucleation rate present similar tendencies with the substrate temperature, despite a large variation in the gas mixture composition. Included is a discussion of the possible reasons for these observations. V
Journal of Materials Research, 2003
In this paper, we present results obtained from a comparison study relating to the deposition of diamond films using two processes, namely, time-modulated chemical vapor deposition (TMCVD) and conventional CVD. Polycrystalline diamond films were deposited onto silicon substrates using both hot-filament CVD and microwave plasma CVD systems. The key feature of TMCVD is that it modulates methane (CH 4 ) flow during diamond CVD, whereas in conventional CVD the CH 4 flow is kept constant throughout the deposition process. Films grown using TMCVD were smoother, harder, and displayed better quality than similar films grown using constant CH 4 flow during CVD. The advantage of using TMCVD is that it promotes secondary nucleation to occur on existing diamond crystals. Pulsing CH 4 , consecutively, at high and low concentrations allows the depositing film to maintain its quality in terms of diamond-carbon phase. Films grown under constant CH 4 flow during diamond CVD displayed a columnar growth mode, whereas with the time modulated films the growth mode was different. The mechanism of film growth during TMCVD is presented in this paper. The growth rate of films obtained using the hot filament CVD system with constant CH 4 flow was higher than the growth rate of time modulated films. However, using the microwave-plasma CVD system, the effect was the contrary and the time-modulated films were grown at a higher rate. The growth rate results are discussed in terms of substrate temperature changes during TMCVD.
Chemical Vapor Deposition of Diamond Films in Hot Filament Reactor
Crystal Research and Technology, 2001
Diamond films of different quality have been synthesized by hot filament chemical vapor deposition (HF CVD) methods from a mixture of hydrogen and hydrocarbon gases. Thin polycrystalline films deposited on silicon substrate were studied using Raman spectroscopy, scanning electron microscopy (SEM) and electron paramagnetic resonance (EPR) technique. Nonuniform distribution of substrate temperatures yields to growth of diamond films in a variety of ways and affects on various types of carbon structures and different kind of defects. The Raman peak shifts to wave number higher than 1332 cm -1 what corresponds to a compressive stress in the range of -0.49 to -1.87 GPa. Two EPR centres with g = 2.003 and ∆H pp equal to 0.65 and 1.2 mT originate from carbon dangling bonds in diamond and in non-diamond phase, respectively.
Investigations concerning the role of hydrogen in the deposition of diamond films
The usual process gases for the chemical vapour deposition of diamond films with hot-filament or microwave techniques contain only a few per cent of a hydrocarbon diluted in hydrogen, because it is often stated that a superequilibrium concentration of atomic hydrogen is required. We performed deposition experiments on Si(l 11) substrates in a microwave plasma without hydrogen dilution. By using Ar-CH 4-02 and Ar-C2H2-02 mixtures, the hydrogen content in the plasma was reduced. Diamond growth took place only in a definite range of gas compositions. Our experiments show that oxygen is partly able to play the role of hydrogen by suppressing the deposition of amorphous or graphitic phases. The phase purity of the diamond films was investigated with Raman spectroscopy and scanning electron microscopy. In order to monitor the plasma chemistry and its changes due to oxygen addition and the reduction ofthe hydrogen concentration, the plasma gas composition was measured with a differentially pumped quadrupole mass spectrometer. The measurements show that oxygen effectively lowers the content of acetylene in the plasma. Our investigations suggest that acetylene is not the main growth species.
Thin Solid Films, 1999
The effect of incorporating oxygen and nitrogen into the feed gases on the texture and surface morphology of diamond ®lm synthesized by hot ®lament chemical vapor deposition (HFCVD) is investigated. The reactant gas composition is determined by the gas¯ow rates. At a constant¯ow rate of hydrogen (33 sccm) and methane (0.68 sccm), the oxygen and nitrogen were varied in the O/(O 1 C) ratio from 0.05 to 0.43 and in the N/(N 1 C) ratio from 0.15 to 0.60. The ®lms were grown under a constant pressure (20 Torr) and a constant substrate temperature (8008C). Clearly nitrogen in the reactant gases has a distinct tendency to promote the k100l texture and the corresponding {100} morphology, whereas oxygen promotes the development of k111l texture and {111} morphology. According to the Wulff theorem (G d 100 =d 111 g 100 =g 111) and the evolutionary selection of crystallites and the surface con®gurations of diamond, the results reveal that during growth nitrogen plays a critical role in activating the C D ±H surface site and consequently increases the surface free energy g 111 , of the {111} surface. In contrast, oxygen activates the C D vH 2 surface site and increases the surface free energy g 100 , of the{100} surface. These results indicate that the texture and the surface morphology of polycrystalline diamond ®lm can be completely controlled by the reactant gas composition.