Plasma high-frequency

The multiple energetic collisions cause molecules to break apart, eventually to form only atoms, both charged and neutral. Insertion of sample molecules into a plasma discharge, which has an applied high-frequency electric field, causes the molecules to be rapidly broken down into electronically excited ions for all of the original component atoms. 

Near the outlet from the torch, at the end of the concentric tubes, a radio high-frequency coil produces a rapidly oscillating electromagnetic field in the flowing gas. The applied high-frequency field couples inductively with the electric fields of the electrons and ions in the plasma, hence the name inductively coupled plasma or ICP. 

A discharge ignited in argon and coupled inductively to an external high-frequency electromagnetic field produces a plasma of ions, neutrals, and electrons with a temperature of about 7000 to 10,000°C. Samples introduced into the plasma under these extremely energetic conditions are fragmented into atoms and ions of their constituent elements. These ions are examined by a mass analyzer, frequently a quadrupole instrument. 

The optoelectronic properties of the i -Si H films depend on many deposition parameters such as the pressure of the gas, flow rate, substrate temperature, power dissipation in the plasma, excitation frequency, anode—cathode distance, gas composition, and electrode configuration. Deposition conditions that are generally employed to produce device-quahty hydrogenated amorphous Si (i -SiH) are as follows gas composition = 100% SiH flow rate is high, --- dO cm pressure is low, 26—80 Pa (200—600 mtorr) deposition temperature = 250° C radio-frequency power is low, <25 mW/cm and the anode—cathode distance is 1-4 cm. 

SNMS sensitivity depends on the efficiency of the ionization process. SNs are post-ionized (to SN" ) either hy electron impact (El) with electrons from a hroad electron (e-)heam or a high-frequency (HF-) plasma (i.e. an e-gas), or, most efficiently, hy photons from a laser. In particular, the photoionization process enables adjustment of the fragmentation rate of sputtered molecules by varying the laser intensity, pulse width, and/or wavelength. 

High-frequency plasma source having no consumable electrodes ... 

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 ... 

It minimizes the potential substrate damage caused by high-intensity ionbombardment, usually found in anstandard high-frequency plasma where the ion energy may reach 100 eV. 

Like diamond, DLC can be obtained by CVD by plasma action in a hydrocarbon atmosphere. Its deposition process differs from that of diamond in as much as the activation is not so much chemical (i.e., the use of hydrogen atoms) but physical. This physical activation is usually obtained by colliding accelerated ions produced by a high-frequency discharge. 

The range of deposition temperature is 755-810°C with a high dilution of nitrogen.When a high-frequency plasma (13.56 MHz) is used, the deposition temperature is lower (400-600°C).P l... 

However, the nitrogen molecule has afar greater bonding energy than ammonia and is more difficult to dissociate into free atomic nitrogen active species. Consequently, the deposition rate is extremely slow. This can be offset by plasma activation with high frequency (13.56 MHz) or electron cyclotron resonance (ECR) plasmasP Ef l and with micro-wave activation. 

Arc Plasma Method The principle of NPs synthesis in this method is based on evaporation by heating and condensation by cooling. The bulk metal is evaporated by heating with electrical resistance, electron beam, or high-frequency magnetics, and subsequently the vapor of metal atoms is condensed on a substrate as a sohd film or particles. In the AP method, electrical charge filled in an external capacitor... 

Somatic hypermutation High frequency of mutation that occurs in the gene segments encoding the variable regions of antibodies during the differentiation of B lymphocytes into antibody-producing plasma cells. 

Solid metal electrodes are usually polished mechanically and are sometimes etched with nitric acid or aqua regia. Purification of platinum group metal electrodes is effectively achieved also by means of high-frequency plasma treatment. However, electrochemical preparation of the electrode immediately prior to the measurement is generally most effective. The simplest procedure is to polarize the electrode with a series of cyclic voltammetric pulses in the potential range from the formation of the oxide layer (or from the evolution of molecular oxygen) to the potential of hydrogen evolution (Fig. 5.18F). 

Fig. 1. Typical a.c. plasma systems used for hydrogenation of semiconductor samples. A. In this aparatus, hydrogen is pumped through the quartz tube (Q) and a plasma excited by inductive coupling of 13.56 MHz r.f. power with a copper coil (c2). The sample rests on a graphite block (b) that is heated by 440 KHz power coupled by a second coil (cl). A pyrometer (P) measures the sample temperature. B. In this system, a high frequency oscillator is used for plasma excitation while the sample is heated in a tube furnace (Pearton et al., 1987).

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