Archaeological fieldwork preceding housing development revealed a Mesolithic site in a primary context. A central hearth was evident from a cluster of calcined flint and bone, the latter producing a modelled date for the start of occupation at 8220–7840 cal bc and ending at 7960–7530 cal bc (95% probability). The principal activity was the knapping of bladelets, the blanks for microlith production. Impact-damaged microliths indicated the re-tooling of hunting weaponry, while microwear analysis of other tools demonstrated hide working and butchery activity at the site. The lithics can be classified as a Honey Hill assemblage type on the basis of distinctive leaf-shaped microlithic points with inverse basal retouch.

Such assemblages have a known concentration in central England and are thought to be temporally intermediate between the conventional British Early and Late Mesolithic periods. The lithic assemblage is compared to other Honey Hill type and related Horsham type assemblages from south-eastern England. Both assemblage types are termed Middle Mesolithic and may be seen as part of wider developments in the late Preboreal and Boreal periods of north-west Europe. Rapid climatic warming at this time saw the northward expansion of deciduous woodland into north-west Europe. Emerging new ecosystems presented changes in resource patterns and the Middle Mesolithic lithic typo-technological developments reflect novel foraging strategies as adaptations to the new opportunities of Boreal forest conditions. While Honey Hill-type assemblages are seen as part of such wider processes their distinctive typological signature attests to autochthonous, regional developments of human groups infilling the landscape. Such cultural insularity may reflect changing social boundaries with reduction in mobility range and physical isolation caused by rising sea level and the creation of the British archipelago.

Basic features of a microcomputer package, BCDP, which is an auto-tutorial designed to teach the Simplex algorithm are described. The package may be used to augment lecture and text materials in introductory linear programming courses or as a review for advanced math programming courses. Preliminary evaluations of the effectiveness of the program to augment classroom instruction are very positive.

This report does not intend to give a complete review of all the papers that appeared since the previous General Assembly but to focus on a few subjects only.

A quantitative study was made of the composition and microstructure of RuO2 films deposited on three different substrates using reactive sputtering. Most of the films had a composition within 2.5 wt.% of the correct stoichiometry; the only exceptions were films grown on Al2O3 (0001) at 150 °C, which had an oxygen-to-ruthenium ratio of 1: 2.24. The excess oxygen was attributed to a thin oxygen-rich layer that encapsulated the grains. Hydrogen concentrations for the films deposited on Al2O3 (0001) were 14, 6, 6, and < 0.5 at.% for room, 150, 300, and 450 °C growth temperatures respectively. The films deposited at room temperature were amorphous on Al2O3 (0001) and SrTiO3 (100), but weakly crystalline on Al2O3 (1102). Highly oriented RuO2 (100) films were produced on Al2O3 (0001) at deposition temperatures ≥150 °C. The in-plane alignment was and a threefold mosaic microstructure was observed. The grain boundaries in these films were discontinuous until the substrate temperature was raised to 450 °C, where coherent grain boundaries were formed. The films grown on Al2O3 (1102) at 450 °C exhibited the epitaxial relationship: RuO2(101)//Al2O3 (1102). The in-plane alignment was RuO2〈101〉//Al2O3〈1101〉, and the lattice parameters were the same as found in bulk RuO2. Transmission electron microscopy indicated a large degree of imperfection in the region between coalescing grains. The RuO2 films grown on SrTiO3 (100) at room temperature were amorphous. The film grown at 450 °C showed a preferential orientation with RuO2 (100)//SrTiO3 (100), but without in-plane orientation.

Sputtered A1N films developed for piezoelectric resonators are extremely chemically reactive. As-sputtered films react with boiling water resulting in a complete loss of the AIN bond structure. Experiments to determine the effect on chemical stability of annealing the sputtered films at 1000 °C, indicate annealing in an oxidizing gas leads to partial oxidation of AlN. Annealing in an inert gas prevents oxidation but does not protect the films from attack by boiling water. Annealing in a reducing gas followed by annealing in an inert gas renders A1N films stable in boiling water. A1N film structure and composition have been studied via Refractive Index, XRD, SIMS, SEM, AES, XPS and FTIR evaluations.

Reactively-sputtered, polycrystalline thin film aluminum nitride (AlN) is an attractive material for use in acoustic wave devices, for which it requires a strong preferred orientation, similar to that found in epitaxial films. This investigation evaluated the grain structure including preferred orientation, grain size, and surface morphology of sputtered A1N films. The characterization techniques utilized included x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results revealed two types of grain structure: 1) a single-grain columnar structure that is perfectly oriented in the [001] direction throughout the entire film thickness and 2) a multiple-grain columnar structure that possesses a strong [001] orientation at the bottom of the film and a tilted [001] combined with other orientations at the top of the film. Strong correlations between orientation and surface morphology, oxygen content, and grain size were observed, namely higher degrees of c-axis orientation correlated with lower mean surface roughness values, reduced oxygen concentration, and narrower grains.

Dimethylethylamine alane (DMEAA) has been used to deposit thin films of aluminum selectively on gold in the presence of silicon oxide. This paper presents studies of the effect of temperature, pressure, and substrate pattern on the selectivity. A specially designed reactor allowed us to probe the structure of the species on the silica surface using infraed spectroscopy. At room temperature two absorptions in the Al-H stretching region were assigned to two species; weakly bound molecules of the intact precursor and a strongly bound dihydride formed from the reaction of DMEAA with surface bound (and H-bonded) hydroxyls (from H2O or silanol groups). At higher temperatures the CH vibrations of the amine disappeared, and the Al-H stretch shifted to higher energy. A weak absorption at 2250 cm−1 attributable to a Si-H also appeared. The impact of these observations on the loss of selectivity is discussed.

GaN thin films have been deposited on Si and sapphire substrates by metalorganic chemical vapor deposition (MOCVD) using diethylgalliumazide and ammonia. Films were grown in the temperature range of 500-750°C. Growth rates were monitored in situ using laser interferometry. The addition of ammonia enhanced the growth rate significantly. At high temperatures, gas-phase depletion of the precursor reduced the growth rate of GaN. Films grown on (0001)-oriented sapphire substrates at temperatures above 650°C were highly textured with smooth surface morphology. Optical and electrical properties of the films are discussed and compared to those of films grown using conventional Ga and N sources.

After a brief introduction on how the differing properties of H2O and NH3 may effect the strategies used to synthesize metal nitrides, an overview of our use of azides to produce aluminum nitride thin films will be presented. The effect of changing the nitrogen source to one which contains at least one N - C bond is to increase dramatically the carbon content of the films. Replacing the alkyl groups attached to the aluminum with hydride ligands removes the final carbon source and forms what appears to be a promising new class of precursors. This is demonstrated by the study of the reaction of Me3NGaH3 with NH3 to produce the novel trimer, [H2GaNH2]3 . This fully characterized molecule converts at 150°C into gallium nitride. Surprisingly, it yields GaN having the sphalerite structure instead of the known wurtzite phase. A discussion of the reasons for this unusual route to a new crystalline phase of GaN is included.

Cyclo-trigallazane, [H2GaNH2]3, is known to form bulk powders of the new cubic phase of gallium nitride upon pyrolysis. An explanation for this unusual example where the molecular structure of the precursor controls the crystal structure of the solid state product is presented. In a hot-wall atmospheric pressure chemical vapor deposition (CVD) reactor, arsine was found to react with TMAG to form films of polycrystalline GaAs which were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The growth rates for smooth films was 1-4 μm/h. In a low pressure CVD reactor, elemental arsenic vapor was also found to react with the TMAG to give GaAs thin films.

Thin films of aluminum nitride have been grown by metalorganic chemical vapor deposition (MOCVD) from diethylaluminum azide. Growth rates of AIN on Si(111) were monitored in-situ with laser interferometry. The growth rate was linear in the partial pressure of the reactant at high temperatures and sublinear at low temperatures. A simple surface reaction mechanism consistent with these observations has been proposed. Surface reaction kinetics and mechanism were further investigated by steady-state kinetic mass spectrometry. Parameters in the growth rate expression were determined by a nonlinear regression of growth rate data. A typical sample of AIN on B-plane sapphire showed a bandgap of about 5.2eV which was increased to 5.9eV upon annealing in nitrogen at atmosphere pressure.

Organometallic aluminum azides have been found to be effective precursors for the low temperature chemical vapor deposition of thin films of aluminum nitride. Quantitative analysis of the gas phase products of the reaction are used to develop an understanding of the reaction. Rate studies of the deposition were performed in the temperature range from 400 to 800°C. Below 525°C, an activation barrier of 26.4 kcal/mol was found, while above 525°C, a value of 5.23 kcal/mol was obtained. The effects of the presence of N-C bonds and the type of Al-N interaction within the precursor are evaluated.