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.

Transmission electron microscopy of GaAs/In x Ga 1−x As/GaAs double heterostructures has enabled the onset and subsequent development of misfit dislocations to be followed for increasing strained-layer thicknesses, from sub-to supercritical. It has been observed that misfit segments are introduced into threading dislocations when the strained-layer thickness is close to, but below, the critical thickness predicted by the Matthews-Blakeslee (M-B) model. Analysis shows that threading dislocations may be able to glide to form interfacial misfit dislocation segments even though the critical thickness predicted by the M-B model has not been reached. It has also been observed that the total dislocation density rises slowly as the layer thickness increases above its critical value, until a sudden increase occurs. It is suggested that the sudden increase in dislocation density is associated with a different mechanism of misfit dislocation formation, which dominates the global relaxation of the structure.

Three non-invasive electrical diagnostic techniques are described. One concerns the RF impedance of a plasma system. The other two are concerned with measurements of species fluxes toward surfaces exposed to plasmas. Examples are presented of their use in low-pressure RF plasmas.