ICMCTF2001 Session D2-2: Synthesis and Characterization of Diamond and Carbon-based Materials

Wednesday, May 2, 2001 1:30 PM in Room Royal Palm 4-6

Wednesday Afternoon

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1:30 PM D2-2-1 Morphology Variation of Diamond With Increasing Pressure Range up to 400 Torr During Deposition Using Hot Filament CVD
M.-S. Kang, W.-S. Lee, Y.-J. Baik (Korea Institute of Science and Technology (KIST), Korea)
The effect of gas pressure and substrate temperature on the diamond crystallite size was investigated during deposition by hot filament CVD. 4 % methane-hydrogen gas mixture was used as precursor gas. Gas flow rate and deposition time were kept constant at 100 sccm and 10 hours. Deposition pressure and temperature were varied between 40 Torr and 400 Torr and between 1020 °C and 1220 °C respectively. The structures of the films were characterized by HRSEM, TEM, XRD and micro-Raman spectroscopy. Typically the diamond crystallite size was decreased as the pressure increased and the temperature decreased. For example, with increasing gas pressure at 1100 °, the structure of the film gradually changed from microcrystalline to nanocrystalline diamond and the non-diamond defect increased. With the substrate temperature increased at 200 Torr, the structure of the film gradually changed from nanocrystalline diamond to microcrystalline diamond. The temperature regime of microcrystalline diamond deposition was observed to be higher as the pressure increased. The typical growth rate of microcrystalline diamond was 1.1 µm/h, but decreased where nanocrystalline diamond formed.
1:50 PM D2-2-2 Thermal Plasma CVD of cBN and Diamond Films - Similarities and Differences
S. Matsumoto, W.J. Zhang (National Institute of Research in Inorganic Materials, Japan)

We have succeeded in synthesizing cBN films on Si substrates by DC plasma jet CVD with substrate bias in an Ar-N2-BF3-H2 gas system1. The gas pressure during the deposition was 50 Torr and the most appropriate substrate bias was -85 V. The phase purity of the cBN films was above 90 % by IR spectroscopy and sharp X-ray diffraction peaks of cBN was observed. Clear Raman peaks of TO and LO phonon modes of cBN appeared for the first time for cBN films. The crystal size was found to be 0.2 x 3 µm by TEM but the crystals contain a large amount of defects such as stacking faults and microtwins. TEM also revealed that presence of interface layers of amorphous and h- or t-BN between the cBN and the substrate. cBN films of above 20 µm in thickness were obtained and the deposition rate at the initial growth stage was 0.3 µm/min. This is the highest growth rate reported so far for cBN films. Positive bias to the substrate or the use of B2 H6 or BCl3 gas, instead of BF3, didn't give cBN under similar deposition conditions.

Our diamond deposition by DC plasma jet or by RF induction thermal plasma from a Ar- H2- CH4 gas system at 140 Torr or at 1 atm gave high quality diamond films with a growth rate of 10 - 2 µm/min. Positive bias to the substrates enhanced the deposition rate, from 6 to 15 µm/min, for example, but negative bias decreased the deposition rate and the crystal quality, inducing the secondary nucleation and the formation of small diamond crystals with {100} faces2.

Thermal plasma CVD is known to give the highest deposition rate of diamond among all the CVD methods so far known. It also gave cBN with high growth rate, although the growth rate was still below one tenth of diamond growth. The deposition of cBN at a pressure as high as 50 Torr suggests the possibility of real CVD of this process, as different from the low pressure (several tens mTorr) CVD reported so far. On the other hand, fluorine and negative bias were necessary for cBN growth. These facts suggest that fluorine is effective for the preferential growth of sp3 bonds as atomic hydrogen is in diamond CVD, but the surface chemistry of the growth is rather different from that of diamond.

1S. Matsumoto and W.J. Zhang, Jpn. J. Appl. Phys. 39 (2000) L442.

2S. Matsumoto et al, Pure & Appl. Chem. 64 (1992) 751.

2:30 PM D2-2-4 Diamond (Heteroepitaxial) Nucleation by Ion Beam Impact: A Reality
S.T. Lee, I. Bello (City University of Hong Kong, China)
The controlled ion beam method was successfully employed for the first time for the systematic nucleation of diamond over a wide range of experimental conditions. Silicon substrates (held at ~700C) were bombarded by ~80-200 eV ions from a source fed by a mixture of hydrocarbon/hydrogen/argon gases at a low (10-4 Torr) pressure. High-resolution TEM analyses confirmed the formation of diamond crystallites in different nucleation sites (on the silicon substrates, adjacent to SiC crystallites, embedded in a non-diamond carbon matrix). Heteroepitaxial diamond crystallites with no misorientation to the silicon substrates were formed on silicon steps. The diamond crystallites existed in the form of both known carbon configurations, i.e., cubic and hexagonal diamond. Most strikingly, among the diamond nuclei we find the first conclusive evidence for the formation of a new diamond polymorph, designated 9R with a periodicity of 9 layers and a rhombohedral structure. The results greatly improve our current understanding of the diamond nucleation process, open a new, controllable way of growing heteroepitaxial diamond films, and demonstrate the capability of ion beams in nanostructuring carbon materials.
3:10 PM D2-2-6 Synthesis of Diamond-Like Carbon Films by Plasma Electrolytic Deposition
S.C. Chung (Industrial Technology Research Institute, Taiwan)
An attempt was made to deposit carbon films on silicon carbide/silicon substrate by plasma electrolytic deposition from organic solution. Substrates were negatively biased with a dc potential of 0 to -500V. The film was observed by scanning electron microscopy and characterized by Raman spectroscopy. The analysis of Raman spectra suggests that the structures of the deposited carbon films depend on the applied bias voltages.
3:30 PM D2-2-7 Metal-Carbon Composite Coatings with Nanostructure: Creation and Properties
M.V. Atamanov, M.I. Guseva, Yu.V. Martynenko, P.G. Moskovkin (Russian Research Center "Kurchatov Institute", Russia); V.S. Mitin (State Center of RF Allrussian Scientific and Recearch Institute of Inorganic Materials, Russia); A.V. Mitin, S.A. Shiryaev (State Center of RF Allrussian Scientific and Recearch Institute of Inorganic Materials, Russian Federation)
A method of Metal-Carbon composite coatings is developed. The method is based on magnetron sputtering with mosaic cathode- target. Metals of IV, V and VI groups were used as targets. Computer modeling of optimal mosaic elements situation in cathode was carried for each case. Amorphous and nano crystalline structures were observed in the coatings by reflection high-energy electron diffraction. High temperature stability of these structures was established. The investigation shows special physical and chemical properties of the films, particularly low friction coefficient and high hardness.
3:50 PM D2-2-8 Comparison of the Structure and the Mechanical Behavior of Conventional and Ca-O-Modified Diamond-Like Carbon Coatings Synthesized by a Direct Current Discharge
A.S. Dorner (Freiberg University of Mining and Technology, Germany); C. Schuerer (Institute of Mechanic and Physical Technologies Chemnitz, Germany); G. Irmer, E. Mueller (Freiberg University of Mining and Technology, Germany)

Diamond-like carbon (DLC) is an amorphous carbon containing a certain fraction of hydrogen. DLC exhibits superior mechanical as well as tribological behaviour and promising biocompatibility. Additional elements like nitrogen, silicon and titanium may effect a further adaptation of the DLC properties according very specific demands. In order to enlarge the applicability of DLC for biomedical purposes, the addition of calcium which is able to influence bone formation may be of considerable relevance. The intention of the study is to gain first information about the influence of Ca-O-incorporation on the mechanical and structural properties of DLC.

The generation of the conventional DLC and the Ca-O-DLC of about 5 µm thickness was carried out by exploiting a direct current discharge for plasma formation. The CaO was dissolved in water. For the generation of Ca-O-DLC, the gaseous precursor (benzene) together with the CaO-H2O vapor is decomposed due to the direct current discharge under a pressure of between 0.005 and 0.05 Pa. For processing conventional DLC, only benzene is supplied into the plasma chamber. The negative bias of the titanium-substrate attracts ions, loaded particles other decomposed fragments and leads to the coating formation.

The characterization of the DLC micro-structure was carried out by Raman spectroscopy and XPS measurements. Hardness determination, scratch and abrasive wear tests give information about the mechanical and tribological performance of the modified coatings. TEM investigations and cell culture tests are planed for gaining further inside about the micro-structure and the biocompatibility of the Ca-O-DLC.

4:10 PM D2-2-9 Wear Resistant Carbon Coatings Deposited Without Substrate Bias Voltage
B. Rother (MAT GmbH Dresden, Germany)
A DC magnetron sputtering process is described which permits the deposition of highly wear resistant carbon coatings without substrate bias voltage. The coatings with a thickness of up to 10 µm are deposited on several materials such as hardened high speed steel and plastics with typical growth rates in the range of 1.5 µm/h. The main structural feature of the coatings is an amorphous carbon network with dominating graphitic bondings. Despite of that structural feature, the coatings exhibit a high wear resistance. The friction coefficient with a hard metal counterbody is in the range of 0.15 and the wear volume is distinctly lower than with other hard coating materials such as TiN or a-C:H.
Time Period WeA Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF2001 Schedule