Chemistry Reference
In-Depth Information
3.7.5 High Voltage Breakdown at Atmospheric Pressure, Corona and
Barrier Discharge .................................................... 107
3.7.5.1
Barrier Discharge ......................................... 109
3.7.6
Glow Discharges at Alternating Electric Field, RF
andMicrowavePlasmas............................................. 110
3.7.6.1
Heating of Electrons in the Bulk Plasma by the
High-Frequency Electric Field ........................... 112
3.7.6.2
Radio Frequency Plasmas ................................ 113
3.8
Technical Plasma Sources .................................................... 115
3.8.1 Introduction .......................................................... 115
3.8.2 Plasma Generation by Electric Fields............................... 115
3.8.3 Low-PressurePlasma................................................ 116
3.8.4 Direct Current Discharges ........................................... 116
3.8.5 Radio Frequency Discharges ........................................ 117
3.8.6 Capacitively Coupled Discharges ................................... 118
3.8.7 Inductively Coupled Discharges .................................... 120
3.8.8 Microwave Discharges .............................................. 121
3.8.9 Atmospheric Pressure Discharges................................... 125
3.8.10 Dielectric Barrier Discharge......................................... 125
3.8.11 Microdischarge....................................................... 128
3.8.12 ColdPlasmaJets..................................................... 130
3.8.13 Beam-Generated Plasmas ........................................... 132
3.8.14 Properties of Plasma Sources for Plasma Chemistry .............. 133
3.8.15 Conclusions .......................................................... 135
3.1 BASIC CONCEPTS OF PLASMA PHYSICS
3.1.1 I
NTRODUCTION AND
B
ASIC
I
TEMS
The name
plasma
defines a quasi-neutral many-particle system (total charge zero)
consisting of sufficient high concentration of free positive (
q
+
) and negative (
q
−
)
charged species, e.g., positive ions, negative ions, and electrons. The system may
contain additionally neutral atoms, molecules, radicals, and excited species. The
classical plasma is characterized by higher mean kinetic energy of electrons or other
plasma species (1-10
5
eV) compared to usual matter, and exceptional electromagnetic
phenomena like the shielding of the far-ranging Coulomb interaction and collective
oscillations of the electron or ion ensemble. Due to the presence of free charged
particles the plasma is electrically conductive. Furthermore, plasmas reveal nonlinear
behavior and have specific dielectric properties, and in interaction of charged plasma
particles with an external magnetic field the plasma shows an anisotropic behavior
concerning the charged particle transport and electromagnetic wave propagation.
3.1.1.1 Classification of Plasmas Concerning Their Energy Content
The plasma state of matter in astrophysics, terrestrial environment, and under arti-
ficial conditions in laboratory stretches over wide ranges in electron concentration
and mean kinetic energy or temperature of charged species. Therefore, the plasma
