A detailed comparison is made between theory and experiment for the low-temperature mobility of holes in gated oxide, coherently strained Si/SiGe heterostructures. We conclude that the mobility is mainly limited by interface impurities, conventional surface roughness and strain fluctuations; by contrast, we argue that alloy scattering is comparatively weak. Comments regarding possible mobility degradation due to oxide formation are also made.

The mechanism of formation of particulate matter (PM) in the diesel engine combustion process is outlined, and the increasingly stringent PM emissions limits in current and projected environmental legislation are noted in the context of the increasing use of fuel-efficient high-performance diesel engines in passenger cars. The types of filter systems for abating diesel particulates are described, as are the principles of filter regeneration – the controlled oxidation of PM retained in the filter, to prevent an accumulation which would ultimately block the filter and degrade engine performance. PM is characterised in terms of both particle size (coarse, accumulation mode, and nucleation mode nanoparticles) and chemical composition, and the filtration issues specific to the various PM types are outlined. Likely future trends in filter design are projected, including multifunctional systems combining PM filtration with NOx control catalysts to meet yet more stringent legislative requirements, including European Stage 5 and 6, and the so called ‘Bin 5’ levels in the U.S.A.

The amidinato compounds [GaMe,L] [L = RNCR'NR (R, R' = H, alkyl or aryl)], [GaMe(PhNCPhNPh),], [GaEt(PhNCMeNPh),] and [Ga(PhNCRNPh),] (R = Me or Ph) have been isolated from the reaction of the appropriate gallium trialkyl with 1, 2 and 3 mol of amidine RNCR'N(H)R, respectively. The chloro derivatives [GaCl,{ RNCR'N(H)R)] (R = Ph or p-ClC,H,; R' = Me) and [GaC12(p-C1C,H,NCMeNC,H,C1-p)l have also been prepared. The compounds have been fully characterised, and mass spectrometric data indicate that the volatile dimethylgallium derivatives exist as either monomers or dimers in the gas phase. X-Ray crystallographic studies on [GaMe,(PhNCPhNPh)] and [GaMe(PhNCPhNPh),] revealed monomeric structures and the presence of chelating amidinate ligands, with distorted tetrahedral and trigonal-bipyramidal co-ordination respectively at the metal centres. Cleavage of the Ga-Me bond occurs on photolysis in the presence of a spin-trapping agent, and thermal decomposition of the solids leads to the formation of gallium nitride.* Non-SZ units employed: G = T, eV z 1.60 x 10 l 9 J.

Measurements of Shubnikov de Haas oscillations in the temperature range 0.3–2 K have been used to determine an effective mass of 0.23 m0 in a Si/Si0.87Ge0.13/Si two-dimensional hole gas. This value is in agreement with theoretical predictions and with that obtained from cyclotron resonance measurements. The ratio of the transport time to the quantum lifetime is found to be 0.8. It is concluded that the 4 K hole mobility of 11 000 cm2 V−1 s−1 at a carrier sheet density of 2.2×1011 cm−2 is limited by interface roughness and short-range interface charge scattering.