Glow-Discharge Microwave Plasma

A glow-discharge (non-isothermal) plasma is generated in a gas by a high-frequency electric field, such as microwave (2.45 GHz), at relatively low pressure.P9] In such a plasma, the following events occur  

In a high-frequency electric field, the gases are ionized into electrons and ions. The electrons, with their extremely small mass, are quickly accelerated to high-energy levels corresponding to 5000K or higher. 

The heavier ions with their much greater inertia cannot respond to the rapid changes in field direction. As a result, their temperature and that of the plasma remain low, as opposed to the electron temperature (hence the name non-isothermal plasma). 

The high-energy electrons collide with the gas molecules with resulting dissociation and generation of reactive chemical species and the initiation of the chemical reaction. 

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). 

---

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

Figure 22-1 Mass spectrum showing natural isotopes of Pb observed as an impurity in brass. [From Y. Su, Y. Duan, and Z. Jin, Development and Evaluation of a Glow Discharge Microwave-Induced Plasma Tandem Source lor Time-ot-Fllght Mass Spectrometry," Anal. Chem. 3000, 72,5600.]...

Su, Y. X., Duan, Y. X., and Jin, Z. (2000) Development and evaluation of a glow discharge microwave-induced-plasma tandem source for time-of-flight mass spectrometry. Anal. Chem., 72, 5600. 

Poljraer surfaces can be easily modified with microwave or radio-frequency-energized glow discharge techniques. The polymer surface cross-links or oxidizes, depending on the nature of the plasma atmosphere. Oxidizing (oxygen) and nonoxidizing (helium) plasmas can have a wide variety of effects on polymer surface wettability characteristics (92). 

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... 

Recently, Hieftje et al.15-16 equipped a small double-focusing mass spectrograph built in house with Mattauch-Herzog geometry with several ion sources (such as glow discharge, an inductively coupled plasma ion source or a microwave plasma torch) and a novel array detector for simultaneous ion detection. 

Inductively Coupled and Microwave Induced Plasma Sources for Mass Spectrometry 4 Industrial Analysis with Vibrational Spectroscopy 5 Ionization Methods in Organic Mass Spectrometry 6 Quantitative Millimetre Wavelength Spectrometry 7 Glow Discharge Optical Emission Spectroscopy A Practical Guide 8 Chemometrics in Analytical Spectroscopy, 2nd Edition 9 Raman Spectroscopy in Archaeology and Art History 10 Basic Chemometric Techniques in Atomic Spectroscopy... 

In 1996, Izuha, Yamamoto and Saito observed the microwave spectrum of H2C=Si produced via a glow-discharge plasma in a gaseous mixture of SiH4 and CO429. The rotational constants deduced were very close to those of Leclercq and Dubois420. The vibrational frequency of the CLL rocking mode was estimated to be 331 5 cm 1, ... 

Plasma CVD has been used since the middle of the 1970s. For the creation of the plasma, DC glow discharge [224], RF glow discharge [219, 225-227], microwave plasma [228, 229], or plasma jets [230] are used. 

The microwave-induced plasma (MIP) is the most popular plasma used for conventional GC-OES. However, the DC glow discharge plasma has recently received more attention because it can be operated at a low temperature, albeit at a low pressure 1-30 Torr so as to avoid excessive gas heating and arcing. 

Figure 1.3 clearly demonstrates the luminous gas phase created under the influence of microwave energy coupled to the acetylene (gas) contained in the bottle. This luminous gas phase has been traditionally described in terms such as low-pressure plasma, low-temperature plasma, nonequilibrium plasma, glow discharge plasma, and so forth. The process that utilizes such a luminous vapor phase has been described as plasma polymerization, plasma-assisted CVD (PACVD), plasma-enhanced CVD (PECVD), plasma CVD (PCVD), and so forth. 

As in the sources used in optical atomic spectrometry a considerable ionization takes place, they are also of use as ion sources for mass spectrometry. Although an overall treatment of instrumentation for mass spectrometry is given in other textbooks [68], the most common types of mass spectrometers will be briefly outlined here. In particular, the new types of elemental mass spectrometry sources have to be considered, namely the glow discharges and the inductively and eventually the microwave plasmas. In contrast with classical high voltage spark mass spectrometry (for a review see Ref. [69]) or thermionic mass spectrometry (see e.g. Ref. [70]), the plasma sources mentioned are operated at a pressure which is considerably... 

---