Hot filament CVD

15 shows a schematic representation of the setup. Normally, the substrate is heated too, thus enabling an exact temperature control. Furthermore, a positive potential may be applied (bias-enhanced CVD), which increases the rates of nucle-ation and film growth. This is because electrons driven by the bias between substrate and filament are extracted from the latter and bombard the substrate. This effect favors dissociation of the hydrocarbon on the surface and thus improves the growth parameters of the film. 

developed by Matsumoto and co-workers at NIRIM, is probably the simplest and most reproducible way to grow diamond at low pressures, and appears to be the easiest to understand experimentally and conceptually. It is also the first method to achieve nucleation and continuous growth of diamond on various substrates. 

In a HFCVD process (Fig. 2a), a gas mixture containing 0.1-2 vol.% CH4 in H2 enters a reactor that is evacuated to approximately 10-100 torr, and flows past a wire or mesh made of a metal such as W, Ta, Mo, or Re, heated to about 2000-2400°C (Tables 1 and 2). Under these conditions, 2-10% of H2 is dissociated into atomic H, and CH4 undergoes pyrolysis reactions leading to the formation of radicals such as CH3 and CH2, and stable species such as C2H2, C2H4, and C2Hg. Diamond is deposited on a substrate made of Si, Mo, or silica, etc., which is mounted at a distance of 0.5 to 2 cm from the glowing filament and kept at 700 to 1000°C either by the radiation from the filament or by a separate substrate heater. 

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Schafer, L., Saltier, M., and Klages, C. P., Upscaling of the Hot-Filament CVD Process for Deposition of Diamond Films on Large-Area Substrates, m Applications of Diamond Films and Related Materials, (Y. Tzeng, et al., eds.), Elsevier Science Publishers, pp. 453-460(1991)... 

Poly crystalline boron nitride films, with a structure similar to rhombohedral boron carbide and a ratio of boron to nitrogen of 3 1, were produced by hot-filament CVD. This work indicates the possible existence of other boron-nitride structures. 

Hot Filament CVD (see Figure 5.2(a)) is relatively cheap and easy to operate and produces reasonable quality polycrystalline diamond films at... 

CVD processes can also be used to grow polymers from nanocarbons. An important example is the coating of a CNT forest with a thin layer of poly(tetrafluorethlylene) (PTFE) via hot filament CVD to produce a superhydrophobic substrate [245]. Here, a vertically aligned MWCNT forest was prepared and placed in a CVD reaction chamber. Hexafluorpropylene oxide gas was then thermally decomposed to form the reactive radical difluorocarbene (CF2) and flowed over the CNT substrate along with a small amount of initiator where direct polymerization of PTFE onto the CNTs occurred [245]. 

MAD was synthesized according to Collioud et a/.8 Silicon wafers with a naturally grown oxide layer (referenced as silicon), CVD deposited Si3N4 on silicon wafers (silicon nitride) and hot filament CVD (HFCVD) deposited... 

Hot filament CVD is another small category of CVD processes that has proven useful in... 

In the case of hot-filament CVD, refractory metal filaments (e.g., W, Ta, Re, etc.) are electrically heated to very high temperatures (between 2000 and 2700°C) to produce the necessary amount of atomic hydrogen that is necessary for the reasons mentioned above for the synthesis of diamond. Except for combustion flame CVD, hot-filament CVD is considered the simplest of all of the methods and also the most inexpensive. Plasma-jet and laser-assisted CVD methods rely on a plasma torch or laser to attain the very high temperatures that are needed to... 

A.7.1. Microwave plasma CVD reactors A.7.2. Hot filament CVD reactor A.7.3. DC plasma CVD reactor A.8. Crystal growth modes A.9. Carbon materials A. 10. Miscellaneous notations... 

This reactor was also invented at NIRIM (NIMS). The structure is very simple. It has a hot filament of W or Ta that is heated to 1900-2200 °C, and placed 5-10 mm above the substrate. The gas pressure P is usually 20 30 Torr. In the electron-assisted hot filament CVD (EACVD) reactor, a negative bias is applied to the filament [219, 448]. 

Figure 3, Diamond crystals grown from 1.5 vol. % CH4-H2 at 10 torr using a combined microwave and hot-filament CVD method, (a) Cube and octahedral faces, (b) twinned crystals with pseudo fivefold symmetry, (c) ball-like diamond grown at high supersaturations the scale in (a)-(b) is 12 pm and in (c) is 15 pm. (Reproduced u/idt pemtissionf American Association far the Advancement of Science, 1988.)...

G. A. Hirata, L. Cota-Araiza, M. Avalos-Boija, M. H. Farias, O. Contreras, and Y. Matsumoto, Nucleation and growth of diamond films on p c-SiCx-Si by hot-filament CVD, J. Phys., 5(33A) A305-306 (1993)... 

J. Wei, J. M. Chang and Y. Tzeng, Deposition of diamond films with controlled nucleation and growth using hot filament CVD, Thin Solid Films, 212(1-2) 91-9S (1992)... 

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