Pressure Radio Frequency Discharge Research Articles

Analysis of particulates generated in a radiofrequency methane plasma by laser light scattering and optical spectroscopy

The generation and the behavior of amorphous hydrogenated carbon particulates have been investigated in a pure methane low pressure radiofrequency discharge at 13.56 MHz. In the plasma, the formation and the presence of two kinds of particulates have been evidenced by use of laser light scattering. The study of the different forces acting on the particulates allowed us to understand their behavior in the discharge. Optical emission measurements have enabled us to correlate the evolutions of the emission lines (CH, H α and H2) with the growth of amorphous hydrogenated carbon particulates and also with the results obtained by laser light scattering. The particulate sizes have been measured and a particulate number density of about 3.0 × 106 cm−3 has been determined.

In Situ Plasma Analysis, Fluorine Incorporation, Thermostability, Stress, and Hardness Comparison of Fluorinated Amorphous Carbon and Hydrogenated Amorphous Carbon Thin Films Deposited on Si by Plasma Enhanced Chemical Vapor Deposition

AbstractIn situ observation of the plasma properties during deposition of fluorinated amorphous hydrogenated carbon (FLAC) and unfluorinated amorphous hydrogenated carbon are performed. The relationship between film properties and impinging ion energy and incident ion momentum is discussed within the framework of existing models of diamond-like carbon (DLC) formation. The DLC films are deposited in a low pressure radio frequency discharge operating at 13.57 MHz with methane and carbon tetra-fluoride as the source gases. Thermostability, stress, and mechanical properties are investigated. The films are elevated to 400 degrees C in order to investigate thermostability. Thin film stress and nano-hardness are also studied. The film density is investigated by gravimetric methods. The fluorinated film stoichiometry is explored with x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.

Characterisation of high voltage pulser performance in radiofrequency plasmas

The performance of a high voltage pulser in plasma immersion ion implantation is strongly influenced by the plasma load into which it operates. There are a number of plasma parameters, such as ion density, potential distribution and ionisation rate, that affect the formation of the cathodic sheath around the workpiece. In turn, these place limitations on the range of voltage, ion current density and duty cycle that is possible to achieve with the pulser. In this paper, we present results of studies into the performance of a 50 kV, 8 A pulser in the ANSTO PI 3 facility (∼ 0.4 m 3). The plasma is a low pressure radiofrequency discharge formed by 300 W of r.f. power at 13.56 MHz applied to a single-loop antenna immersed in a plasma with an ion density of approximately 10 9 cm −3 and filling pressure of 0.5–5 × 10 −3 mbar. The plasma parameters can be altered by varying the r.f. power, the plasma potential, the gas mixture and the filling pressure. Optical emission spectroscopy has shown a large increase in emission from atomic species that are sputtered from the surface of the workpiece during the high voltage pulse. This emission decays very rapidly when the high voltage pulse is terminated.

Emission spectroscopy and actinometry in a magnetized low pressure radio frequency discharge

A low pressure 13.56 MHz radio frequency (rf) discharge is generated between two coaxial cylindrical electrodes, and is confined by two different types of magnetic field. A plasma electron temperature Te of typically a few electron volts is estimated from experimental spectroscopic data. Application of a homogeneous magnetic field appears to lower this Te by a few tenths of electron volts. Spatially resolved emission spectroscopy in an argon disharge shows that the magnetic confinement of plasma electrons leads to nonuniform emission intensities. The observed distributions can be related to ion density profiles, which have been measured with a Langmuir probe. It is shown that, at the low gas pressures considered here (several milliTorr), metastable states play an important role in the excitation and ionization mechanisms sustaining the discharge. Both experimental and theoretical arguments are presented to support this view. Actinometric measurement of the relative fluorine density in a magnetized CF4 discharge indicates a high density of fluorine radicals. Only at low pressures an additional increase of the fluorine density is observed for higher magnetic field strengths.

Plasma deposition and Auger studies of carbon impurities in zinc oxide

A low pressure radio-frequency discharge in methane or a methane-oxygen mixture is used to deposit carbon species on the surface of compacted ZnO powder at 400° C. The carbon composition of the treated samples is examined in a separate Auger spectrometer system as the samples are heated in vacuum to 400° C, exposed at 400° C to oxygen, reannealed at the same temperature and subjected to argon ion bombardment. Evidence is presented that in the case of ZnO treated in methane-oxygen discharges, volume incorporation of carbon occurs and that this carbon moves to the surface of the sample in the course of subsequent vacuum heat treatment.