The radio-frequency-induced plasma polymerization of allylamine has been investigated in the plasma-gas phase by mass spectrometry and at the plasma−solid interface by means of an ion flux probe and a quartz mass balance. The surface chemistry of the deposits has been determined by X-ray photoelectron spectroscopy. The objective of this study was to unravel the mechanism(s) by which allylamine plasma polymers form. The results are compared with those obtained in an earlier investigation of the plasma polymerization of acrylic acid. In the plasma-gas phase, evidence is provided for reactions between cations and intact neutral monomers (allylamine). These oligomerization reactions were found to be relatively power-insensitive compared with those seen in plasmas of acrylic acid, as was the gas-phase concentration of the intact neutral monomer. At the polymer surface, ion fluxes were found to increase with plasma input power (P) from 6.6 × 1016 ions m-2 s-1 at 1 W to 1.4 × 1018 ions m-2 s-1 at 14 W. The ionic mass transport to the polymer surface (ion mass flux) was calculated by multiplying the measured ion flux by the average ion mass (determined by mass spectrometry). At P = 1 W, the ion mass flux was 11.7 μm m-2 s-1, and at 14 W, the ion mass flux was 226.6 μm m-2 s-1. These values differed from the total mass deposition rates measured by the quartz mass balance, which were 18.7 and 127.1 μm m-2 s-1, respectively. However, the relationship found between the ion mass flux, the mass deposition rate, and P was complex, and it is shown that, at very low P (<1 W), the ion mass flux is sufficient to account for all of the deposit.

Ion Ñux, mass spectral and mass deposition rate measurements have been made in radiofrequency-induced continuous-wave plasmas of acrylic acid. At 1 W input power, an ion Ñux of 0.05 ^0.1 ] 1018 ions m~2 s~1 was measured for acrylic acid. At this power, ions corresponding to (2M ] H)`and (3M ] H)`were prominent in the positive-ion mass spectrum. When this spectrum was corrected for the transmission function of the quadrupole mass spectrometer (conservatively taken as intensity P m~1), it was evident that the cationic portion of plasma contained many ions of high m/z, as opposed to small fragments of acrylic acid. The m/z of the " average Ï ion was calculated as 115. The mass of ions arriving at a solid surface in the centre of the plasma was then calculated by multiplying the Ñux by the average mass to give 9.6 lg m~2 s~1. This value represents a signiÐcant fraction of the total mass deposited, determined by means of a quartz crystal mass balance (45.5 lg m~2 s~1). Repeating the calculation for a 5 W plasma yields an ion mass Ñux of 39.6 lg m~2 s~1 (measured mass deposition of 57.3 lg m~2 s~1). At 15 W, the calculated mass deposited (based on ion Ñux) exceeds that measured by the quartz mass balance. The " average Ï ion mass decreased as plasma input power increased.Based on these data, and XPS measurements of the solid-phase deposit we make a Ðrst attempt at describing semi-quantitatively the possible role of ions in deposit formation.

This article describes how to extract accurate information about a plasma from a capacitively coupled planar probe that is biased using pulsed radio-frequency excitation. The conditions necessary to observe correct saturation of the probe current are investigated, particularly the use of correct geometry and biasing for the guard ring. With these precautions the probe is an effective diagnostic for electron tail temperature at energies beyond those probed by conventional cylindrical probes. The dynamic response of the probe is investigated using conventional sweep voltages and shows the onset of displacement current and inertial effects associated with ions and electrons. In addition the effect of insulating films on the probe surface is examined, showing how the probe continues to operate even when it is coated. Characteristic changes caused by the presence of an insulating film give information about its electrical properties and its thickness.

Assuming a background Maxwellian electron distribution we investigate the effects of tailoring the tail of the distribution upon the plasma density and electron temperature in a capacitive discharge. Taking the latter to be in the intermediate pressure regime the main effect of the tail is to modify the rate coefficients for ionization and excitation, and hence to alter the collisional energy loss per electron-ion pair created. We demonstrate that the background temperature can be suppressed and the electron density increased by enhancing the tail population. The model is applied to a typical set of low temperature conditions in argon and the changes in temperature and density calculated. Injecting 100 eV electrons into an argon plasma under very similar conditions to those of the application of our model, the corresponding densities and temperatures are measured. Good qualitative agreement is found.