Microwave plasma reactor

Figure 5.2. Two of the more common types of low pressure CVD reactor, (a) Hot Filament Reactor - these utilise a continually pumped vacuum chamber, while process gases are metered in at carefully controlled rates (typically a total flow rate of a few hundred cubic centimetres per minute). Throttle valves maintain the pressure in the chamber at typically 20-30 torr, while a heater is used to bring the substrate up to a temperature of 700-900°C. The substrate to be coated - e.g. a piece of silicon or molybdenum - sits on the heater, a few millimetres beneath a tungsten filament, which is electrically heated to temperatures in excess of 2200 °C. (b) Microwave Plasma Reactor - in these systems, microwave power is coupled into the process gases via an antenna pointing into the chamber. The size of the chamber is altered by a sliding barrier to achieve maximum microwave power transfer, which results in a ball of hot, ionised gas (a plasma ball) sitting on top of the heated substrate, onto which the diamond film is deposited.

Coupled with the relative ease of scaling microwave plasma reactors to a size pertinent to industrial coating operations (11), these features place microwave plasma processes into the domain of industrial relevance. 

The fluorination of the inner surface of intravenous tubing, using atmospheric pressure plasma glow (APG), has been evaluated to enhance biocompatibility and suppress plasticiser migration (273). The effect of plasma treatment on the migration of DOA, and an EVA-carbon monoxide terpolymer as partial or complete replacement, into isooctane solution has given positive results (231). A closed system microwave plasma reactor was used to react imidazole molecules to PVC surfaces with the claim that the resulting PVC was useful as an implant for biomedical applications, on the basis of spectroscopic studies (368). 

Huang J, Badani MV, Suib SL, Harrison JB, Kablauoi M. Partial oxidation of methane through microwave plasmas. Reactor design to control free-radical reactions. J Phys Chem 1994 98 206-10. 

A closed-system microwave plasma reactor was used to react imidazole molecules to PVC surfaces. Newly created... 

High levels of boron incorporation are desired for applications where low resistivity is required. The boron incorporation on (ill) faces is approximately ten times greater than on (100) faces [51, 52]. Also, higher boron levels are achieved in hot filament reactors than in microwave plasma reactors [53]. The presence of oxygen in the reaction gas greatly reduces the concentration of boron incorporated in the diamond, presumably because of the formation of stable oxides of boron [54-57]. These results on boron incorporation are summarized in the review by Angus et al. [20]. 

Microwave-Plasma Deposition. The operating microwave frequency is 2.45 GHz. A typical microwave plasma for diamond deposition has an electron density of approximately 10 electrons/m, and sufficient energy to dissociate hydrogen. A microwave-deposition reactor is shown schematically in Fig. 5.18 of Ch. 5.P ]P°]... 

Electron Cyclotron Resonance (ECR). A microwave plasma can also be produced by electron cyclotron resonance (ECR) (see Ch. 5, Sec. 9). An ECR-plasma reactor suitable for the deposition of diamond is shown schematically in Fig. 5.19 of Ch. 5.[ °]... 

The new method produces TiN powders with surface areas exceeding 200 m g that are otherwise only accessible using a forced flow reactor and a microwave plasma activator in which titanium metal is reacted with N2 in the gas phase [14]. TiN powders with considerably lower specific surface area (Sg<60m g ) were also synthesized using the nitridation of 10-15 nm-sized... 

Microwave Plasma CVD reactors use very similar conditions to hot filament reactors, and despite being significantly more expensive, are now among the most widely used techniques for diamond growth. In these... 

The ACTIS process described above is a typical example of low-pressure plasma polymerization or LCVD, which is an ultimate green process with no effluent in the practical sense. Microwave plasma is used for plasma polymerization of acetylene. ACTIS process, as an example of LCVD, has an ideal combination of unique advantages in (1) very high reaction yield (monomer to coating), (2) no effluent from the process, (3) no reactor wall contamination because the reactor wall is the substrate surface, and (4) very short reaction time. However, whether such an ideal LCVD process is an industrially viable practice is a totally different issue. 

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... 

There are several types of microwave plasma CVD (MPCVD) reactors designed by several organizations. The widely known reactors are presented in Section 3 ... 

NIRIM-type A microwave plasma CVD reactor developed by National Institute for Research in Inorganic Materials (NIRIM), Japan. This laboratory is now called National Institute for Materials Science (NIMS). 

Microwave-assisted fabrication of ceramic coatings on fibers and powders can be done at intermediate temperatures. For example, at temperatures of about 800-900° C, carbon fibers have been coated with thin TiN layers using a microwave plasma-assisted fluidized bed with the precursor vapor (TiCU in this case) being introduced into the reactor by the fluidizing gas. ... 

Sample Preparation. Cobalt catalysts were prepared by subliming Co2(C0)g into the pores of dehydrated NaX zeolite in a vacuum line at pressures of 1 x 10- f torr. Argon was flowed over the metal loaded zeolite sample at a pressure of 0.3 torr. A microwave plasma was induced with a static gun and the decomposition of the metal carbonyl precursor occurred for two hours. After total decomposition of the metal carbonyl which can be determined by the color of the plasma, the argon flow was stopped and the sample was sealed off by closing the Teflon stopcocks at both ends of the reactor. The sample was then brought into a drybox and loaded into catalytic reactors or holders for spectroscopic experiments. Further details of this procedure can be found elsewhere (11, 25). Iron samples were prepared in a similar fashion except ferrocene was used as a metal precursor. 

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