Plasma, microwave

Thermal ionization. Takes place when an atom or molecule interacts with a heated surface or is in a gaseous environment at high temperatures. Examples of the latter include a capillary arc plasma, a microwave plasma, or an inductively coupled plasma. 

Hot RF and - DC plasma, are discharge, plasma jets Oxy-acetylene flames Low pressure microwave plasma, holt filament. Low pressure DC or RF glow discharge Thermal decomposition... 

SOME NEW ADVANCES IN DEVELOPING MICROWAVE PLASMA TORCH SPECTROMETRY... 

A new, low-pressure, plasma-assisted proeess for synthesising diamonds has been found by Roy et al [83,84]. An intimate mixture of various forms of carbon with one of many metals (e.g., Au, Ag, Fe, Cu, Ni) is exposed to a microwave plasma derived from pure hydrogen at temperatures ranging from 600-1000 °C. Roy et al postulate a mechanism in which a solid solution of atomic hydrogen and the metal. Me, facilitates dissolution of carbon to form molten droplets of Me -Cj,-H. Diamonds nucleate at the surface of the droplets as the temperature is reduced. 

Handbook of Chemical Vapor Deposition 9.3 Glow-Discharge (Microwave) Plasma... 

The most common frequencies in use for CVD are micro-wave (MW) at 2.45 GHz and, to a lesser degree, radio frequency (RF) at 13. 45 MHz (the use of these frequencies must comply with federal regulations). A microwave-plasma deposition apparatus (for the deposition of polycrystalline diamond) is shown schematically in Fig. 5.18 (see Ch. 7, Sec. 3.4). 

Figure 5.18. Microwave plasma apparatus for the deposition of diamond.

A microwave plasma can also be produced by electron cyclotron resonance (ECR), through the proper combination of electric and magnetic fields.Cyclotron resonance is achieved when the frequency of the alternating electric field is made to match the natural frequency of the electrons orbiting the lines of force of the... 

Most CVD-diamond processes require a plasma (see Ch. 5. Sec. 9). Two types of plasma are currently used for the deposition of diamond microwave plasma (non-isothermal) and arc plasma (isothermal). 

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°]... 

Plasma-arc diamond deposition is produced at a higher pressure than in a microwave plasma (0.15 to 1 atm). At such pressure, the average distance traveled by the species between collisions (mean free path) is reduced and, as a result, molecules and ions collide more frequently and heat more readily. 

By increasing the electrical energy in a fixed amount of gas, the temperature is raised and may reach 5000°C or higher.P i Such high temperatures produce an almost complete dissociation of the hydrogen molecules, the CH radicals, and other active carbon species. From this standpoint, arc-plasma deposition has an advantage over microwave-plasma or thermal CVD since these produce much less atomic hydrogen. 

The substrate temperature should be kept between 800 and 1000°C and cooling may be necessary. Gas composition and other deposition parameters are similar to those used in a microwave-plasma system. Deposition rate is low, reported as 0.5 to 1 im/h. 

A composite film of SiC and diamond was produced from tetramethylsilane, hydrogen, and methane in a microwave plasma on single-crystal silicon wafers. Volume fraction of the components can be adjusted by varying the gas composition. 

Another MOCVD reaction uses a microwave plasma to decompose iron cyclopentadienyl, (C5H5)2Fe, in an oxygen atmosphere in a temperature range of 300-500°C and at low pressure (1-20 Torr).[39]... 

Inside" processes—such as modified chemical vapor deposition (MCVD) and plasma chemical vapor deposition (PCVD)—deposit doped silica on the interior surface of a fused silica tube. In MCVD, the oxidation of the halide reactants is initiated by a flame that heats the outside of the tube (Figure 4.8). In PCVD, the reaction is initiated by a microwave plasma. More than a hundred different layers with different refractive indexes (a function of glass composition) may be deposited by either process before the tube is collapsed to form a glass rod. 

The U.S. electronics industry appears to be ahead of, or on a par with, Japanese industry in most areas of current techniques for the deposition and processing of thin films—chemical vapor deposition (CVD), MOCVD, and MBE. There are differences in some areas, thongh, that may be cracial to future technologies. For example, the Japanese effort in low-pressure microwave plasma research is impressive and surpasses the U.S. effort in some respects. The Japanese are ahead of their U.S. counterparts in the design and manufacture of deposition equipment as well. 

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... 

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.

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... 

In addition to microwave plasma, direct current (dc) plasma [19], hot-filament [20], magnetron sputtering [21], and radiofrequency (rf) [22-24] plasmas were utilized for nanocrystalline diamond deposition. Amaratunga et al. [23, 24], using CH4/Ar rf plasma, reported that single-crystal diffraction patterns obtained from nanocrystalline diamond grains all show 111 twinning. 

Whereas a microwave plasma is most commonly used for the PE-CVD of diamond films, an ECR is the only plasma that is used for diamond deposition below 1 Torr [27-29]. Although Bozeman et al. [30] reported diamond deposition at 4 Torr with the use of a planar ICP, there have been a few reports that describe the synthesis of diamond by low-pressure ICP. Okada et al. [31-33] first reported the synthesis of nanocrystalline diamond particles in a low-pressure CH4/CO/H2 ICP, followed by Teii and Yoshida [34], with the same gas-phase chemistry. 

Microwave plasma detection has been reviewed [351], also in relation to GC [352,353], Coupling of chromatography (GC, SFC, HPLC) and capillary electrophoresis (CE) with ICP-MS and MIP-MS detectors has also been reviewed [181,334,335]. Various specific GC-ICP-MS reviews have appeared [334,337,345,346,354,355]. 

Srikanfh, H., Hajndl, R., Chirinos, C. and Sanders, J. (2001) Magnetic studies of polymer-coated Fe nanopartides synthesized by microwave plasma polymerization. Applied Physics Letters, 79, 3503-3505. 

Gate Oxide Tunnel Oxide f SiH4/N20 PECVD Microwave Plasma Anodisation Laser CVD... 

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