Effect of argon and substrate bias on diamond thin film surface morphology (original) (raw)
Related papers
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2001
Diamond films of small roughness have been deposited onto thermally oxidized Si substrates by a process of anisotropic crystalline growth induced by nitrogen in a hot-filament chemical vapor deposition reactor. Ethanol (C2H5OH), diluted in hydrogen and nitrogen, was used as the source of carbon. At high concentrations, nitrogen tends to suppress the diamond growth in the 〈100〉 direction, which allows the growth of square mesoscopic-like crystals (“plates”) of large area in the directions parallel to the surface of the substrate. These plates stack upon each other, forming a thick diamond coating of uniform thickness. Analysis of the films made by micro-Raman spectroscopy and atomic force microscopy revealed that it is possible to obtain diamond coatings of high quality with a roughness comparable to that of the SiO2 at the diamond/SiO2 interface, and of nanometric roughness on the surface of the plates. A model to explain the morphology of the plates based on the microscopic mechani...
This paper focuses on reporting systematic studies on the effect of the precursor gas chemistry ratio between hydrogen/methane (H 2 /CH 4) and argon (Ar) to tailor control of the grain size, morphology and roughness of large area diamond films. Films ranging from a microcrystalline diamond structure (MCD 1–3 μm grain size) all the way to an ultrananocrystalline diamond (UNCD 3–7 nm grain size) structure were grown over 100 mm diameter areas, as a pathway for scaling diamond film growth processes by Hot Filament Chemical Vapor Deposition (HFCVD) to large areas (≥150 mm in diameter). H 2-rich/CH 4 chemistry was used to synthesize the MCD films, while Ar-rich/CH 4 /H 2 chemistry was used to grow the UNCD films. The synthesis of the diamond films using the HFCVD process indicates that the Ar content is critical to achieve the characteristic UNCD film structure with roughness , chemical bonding and thickness uniformity in the range of 5% across large areas. The ratio of Ar/H 2 in the range 70/30 sccm to 90/10 sccm, all with 2 sccm of CH 4 gas, yields films with grain size from 10–50 nm for nanocrystalline diamond (NCD) films to 3–7 nm for the UNCD films, respectively. The extremely smooth UNCD films (~3–5 nm rms) are achieved using Ar (90 sccm)/H 2 (10 sccm)/CH 4 (2 sccm) gas flows.
Bulletin of Materials Science, 2014
Polycrystalline diamond thin films with outgrowing diamond (OGD) grains were deposited onto silicon wafers using a hydrocarbon gas (CH 4) highly diluted with H 2 at low pressure in a hot filament chemical vapour deposition (HFCVD) reactor with a range of gas flow rates. X-ray diffraction (XRD) and SEM showed polycrystalline diamond structure with a random orientation. Polycrystalline diamond films with various textures were grown and (111) facets were dominant with sharp grain boundaries. Outgrowth was observed in flowerish character at high gas flow rates. Isolated single crystals with little openings appeared at various stages at low gas flow rates. Thus, changing gas flow rates had a beneficial influence on the grain size, growth rate and electrical resistivity. CVD diamond films gave an excellent performance for medium film thickness with relatively low electrical resistivity and making them potentially useful in many industrial applications.
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.
Structure of diamond polycrystalline films deposited on silicon substrates
Vacuum, 2010
The article presents results of structural studies of polycrystalline diamond thin films deposited by hot filament CVD on silicon substrates. The films were characterized using Scanning Electron Microscopy (SEM), Raman Spectroscopy (RS), Electron Backscattered Diffraction (EBSD), Energy Dispersive Spectroscopy (EDS) and Secondary Ion Mass Spectroscopy (SIMS). Both the EBSD patterns and Raman spectra confirm that the grains visible in the electron micrographs are diamond micro-crystallites. The residual stress in the films is found to be in the range between À4.29 GPa and À0.56 GPa depending on the sample thickness. No evidence of lonsdalite and graphite has been registered in the polycrystalline material of the investigated samples. Evidence of the existence of silicon carbide at the diamond/silicon interface is presented. It is also suggested that an amorphous carbonaceous film covers the silicon surface in the regions of holes in the thin diamond layers.
Journal of Crystal Growth, 2004
A study on the effect of growth kinetics and properties of diamond film obtained by addition of argon (B7 vol%) into the methane/hydrogen mixture is carried out using a hot-filament chemical vapor deposition system. A negative bias was used as a nucleation enhancement method in addition to the argon dilution. The scanning electron microscopic images show well faceted crystallites with a predominance of angular shapes, corresponding to /1 0 0S and /1 1 0S crystalline surfaces. The surface nucleation density and growth rate with argon dilution is found to be two orders of magnitude higher than those without argon dilution. The micro-Raman spectra show a good-quality film whereas X-ray photoelectron spectra show existence of only carbon phase (C 1s peak). The effect of argon dilution on the microstructure of the diamond is discussed in the view of reported literature. r
Nanocrystalline Diamond Thin Films Synthesis on Curved Surface
Plasma Chemistry and Plasma Processing, 2014
Thin films of curved surface nanocrystalline diamond (CS-NCD) are a category of important materials. However, the development of such materials is still a highly challenging task. Here we present a novel approach to synthesizing CS-NCD thin films deposited on non-spherical surfaces of molybdenum substrate using direct current plasma jet chemical vapor deposition. A special cooling system was designed and applied to ensure uniform substrate temperature. It is demonstrated from simulation and experimental results that this system is favorable for the production of thin films. The results show that the quality of CS-NCD thin films depends on the selection of optimal values of parameters including CH 4 concentration, substrate temperature, and chamber pressure. If the CH 4 concentration and/or the substrate temperature is too high or low, it results in non-diamond phase or micron-crystalline diamond thin films. Synthetic CS-NCD thin films using the proposed method have a smooth surface and uniform thickness. The average grain size and the mean surface roughness are approximately 30 and 4.3 nm respectively. Characteristics of CS-NCD thin film spectra comprised of the full width at half maximum with broad Raman peaks around 1,140 and 1,480 cm -1 , confirming the presence of the NCD phase.
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.
Microcrystalline diamond (MCD) films were deposited using a conventional hotfilament chemical vapor deposition (HFCVD) system on 4" N-type Si (100) substrates at 30 mbar and 2800 watt for 20 hours. The methane and hydrogen gas flows were 3 sccm and 300 sccm, respectively while the oxygen flow was varied from 0.01 sccm to 0.04 sccm corresponding to 0.2% to 0.8% of methane. The films obtained were characterized using x-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) for their structure, quality and morphology, respectively. The resistivity was calculated by van der Pauw technique, current and voltage were measured using semiconductor device analyzer. It was found that growth rate and grain size increased gradually for higher concentrations of oxygen and resistivity decreased continuously whilst surface morphology varied significantly with the addition of O 2. The enhanced growth rate was correlated with the enhanced atomic hydrogen as well as O 2 /C 2 ratio with increasing oxygen concentration and the drop in resistivity was correlated with a rise in the local defects caused by the addition of oxygen to the CVD chamber. Low resistivity polycrystalline diamond films with larger grain size can be achieved by adding very small amount of O 2 while keeping other parameters constant. These low resistivity diamond films can be used for various electronic applications and as substrates for cells cultivation. It can also be used for bio applications such as biosensors or tissue engineering.
Growth of Nitrogen-Incorporated Diamond Films Using Hot-Filament Chemical Vapor Deposition Technique
Advanced Science Letters, 2013
Micro-and nanocrystalline diamond (MNCD) films were deposited on silicon substrates by hot-filament chemical vapor deposition (HF-CVD) at chamber pressure of 22.5 torr for 20 hours. The total mass flow rate was 300 sccm (3 Vol.% CH 4 , while the nitrogen gas flow rate was varied from 0.04 to 0.64 sccm corresponding to 0.8 to 12.8% of H 2 + CH 4 mixture. The resulting films were characterized by X-Ray Diffraction (XRD), Raman Spectra, Scanning Electron Microscope (SEM) and four point probe van der Pauw method to analyze and measure the structure, quality, morphology and resistivity of the deposited films, respectively. Results show that the grain size increases at low concentration of nitrogen, while it decreases for high concentration of nitrogen and the fact is probably the formation of atomic nitrogen N o near filament surface and its inward diffusion on the surface of growing film. Resistivity decreases continuously due to formation of C H bonds in a trans-polyacetylene structure along with diamond film, which leads to change surface morphology. By increasing nitrogen content enhance distortion along [111] direction of the resulting films.