Low-temperature radio frequency plasmas are essential in various sectors of advanced technology, from micro-engineering to spacecraft propulsion systems and efficient sources of light. The subject lies at the complex interfaces between physics, chemistry and engineering. Focusing mostly on physics, this book will interest graduate students and researchers in applied physics and electrical engineering. The book incorporates a cutting-edge perspective on RF plasmas. It also covers basic plasma physics including transport in bounded plasmas and electrical diagnostics. Its pedagogic style engages readers, helping them to develop physical arguments and mathematical analyses. Worked examples apply the theories covered to realistic scenarios, and over 100 in-text questions let readers put their newly acquired knowledge to use and gain confidence in applying physics to real laboratory situations.

No abstract

A criterion for the positive-ion velocity at the boundary of an electronegative plasma is discussed. The case considered is that in which the negative-ion density obeys the Boltzmann relation. The appropriate physical solution is determined in circumstances where a triple-valued mathematical solution is found. The work has much in common with models of two-electron-temperature plasmas. Under conditions where the theory is valid, the ratio of negative-ion density to positive-ion density can be determined from Langmuir probe characteristics.

A novel electrostatic probe method is described in which the ion flux is determined from the discharging of an RF-biased capacitance in series with the probe. By using a large-area planar probe, with a guard ring and located in or on other surfaces, edge effects and perturbations to the plasma volume can be kept small. The ion flux to the probe can be determined even when its surface is coated with insulating material from the plasma itself. Results are reported for ion fluxes in RF-excited plasmas in Ar and in CF 4 in a RIE reactor. In Ar, ion fluxes to the earthed surfaces increase with pressure and power over the ranges 50-200 mTorr and 30-200 W. In CF 4 , over the same ranges the ion fluxes to the surfaces decrease with increasing pressure.

This is a tutorial article. An introductory discussion of direct current gas discharges is presented. Beginning with basic ideas from kinetic theory, gas discharge plasmas are described in terms of phenomena observed in the laboratory. Various models are introduced to account for electrical breakdown, plasma boundaries and the longitudinal and transverse structure of discharges.

This work investigates the use of hairpin probes in plasma where RF plasma potential is present. The microwave resonance of the hairpin is used to determine electron density. Two types of hairpin probe were used. One type was dc coupled: its dc potential could be varied while monitoring its resonance frequency and collected current. The other probe was designed to be fully floating, being (dc) isolated from ground and able to float with RF variations in the plasma potential. Additional measurements of the RF plasma potential and its effect on the dc floating potential of the former probe were made using a wire loop probe. The resonant frequency of the dc coupled probe at zero current (nominal floating potential) was less than that determined from the fully floating probe. This is attributed to the wider sheath around the former caused by RF plasma potential across it. The presence of the electron-free sheath around the wires of the hairpin is included in the analysis that links the resonant frequency to the electron density in the bulk plasma. When the dc coupled probe was biased at the true floating potential (determined from independent loop probe measurements) its resonant frequency was closer to, though still consistently higher than, that of the floating probe. This work shows that RF potential across the probe sheath affects the resonance of a hairpin probe and should be accounted for when using hairpin probes in discharges where RF plasma potential variations are even as low as a few times the electron temperature (in volts).

Recently, there have been enormous efforts to tailor the properties of graphene.These improved properties extend the prospect of graphene for a broad range of applications. Plasmas find applications in various fields including materials science and have been emerging in the field of nanotechnology. This review focuses on different plasma functionalization processes of graphene and its oxide counterpart. The review aims at the advantages of plasma functionalization over the conventional doping techniques. Selectivity and controllability of the plasma techniques opens up future pathways for large scale, rapid functionalization of graphene for advanced applications. We also emphasize on atmospheric pressure plasma jet as the future prospect of plasma based functionalization processes.

A retarding field analyser has been used to examine ion and electron energies at the grounded electrode of a capacitively coupled RF discharge in argon. The onset of collisional scattering of the ion distribution was observed at 0.05 mbar. A Tonks-Langmuir-type model has been used to generate a theoretical collision-free energy distribution which compares well with results at low pressure. The energies of electrons incident on the electrode were not consistent with the high-energy tail of a simple Maxwellian distribution in the plasma, and are better modelled by a two-temperature distribution.