Grain boundaries (GBs) in polycrystalline materials play a pivotal role in controlling their mechanical and physical behavior. High-resolution electron microscopy (HREM) was used to study thermally activated GB migration in thin films of Al and Au at elevated temperatures (T > 0.5 Tm). Grain boundary engineering via epitaxial templating allowed the manufacture of well-defined grain and interfacial geometries. These techniques enabled the observation of tilt, but also twist and general GBs at atomic resolution in-situ at high temperatures. Surface-energy driven GB migration occurred in general GBs, whereas tilt GB motion was curvature driven. Digital analysis of HREM video recordings have given considerable insight in the dynamics of GB motion at elevated temperatures. It is not surprising that the complex and diverse migration mechanisms depend on GB geometry as well as on interatomic interactions. The results provide, among others, direct evidence for collective effects by concerted atomic shuffles, ledge propagation in (113) symmetric tilt GBs, and motions of triple junctions at elevated temperatures.

We report on version 1.0 of the Edinburgh/AAO/Strasbourg catalogue of new and possible Planetary Nebulae (PN) distributed via cdrom at this meeting. We provide accurate positions, designations, images and other descriptive parameters for the PN. In future releases this will be supplemented by inclusion of spectra and related material such as line ratios, velocities etc.

The 900+ PN have been discovered solely from visual scrutiny of narrow-band exposures taken for the AAO/UKST H-alpha survey of the Southern Galactic Plane. Most have classic PN-type morphologies (i.e. bi-polar, rings, shells or ovals). SuperCOSMOS data will soon supersede our visual scanning but it proved an effective preliminary technique to identify candidate PN on the basis of morphology, isolation and identification as an H-alpha nebulosity. We already have confirmatory spectroscopy for ~ 700 objects. Much of our new sample are of very low surface brightness, with no obvious central star, and so have remained undetected in previous surveys. They are revealed here due to the excellent depth, resolution, coverage and uniformity of the H-alpha survey. Many PN are also well extended. The average angular size is 51″ with the median of 27″ but examples extend to several arcminutes. This may indicate many are in a highly evolved state where the central star has faded from easy optical detection and the nebula itself is dissipating into the ambient ISM. Large numbers of candidate PN have also been found in the Galactic Bulge region, most of which have been confirmed via UKST FLAIR/6dF MOS spectroscopy (Parker et al, in preparation and these proceedings).

By version 2.0 (release in 2002) we will have doubled the number of Galactic PN accrued from all sources over the last 75 years. This new catalogue should have a profound impact on many aspects of PN research.

An anterior neopharyngeal diverticulum is a recognized cause of dysphagia following laryngectomy. It is easily treated by endoscopic stapling.

GaN grown on sapphire (α–Al2O3) was characterized by laser-induced molecular beam epitaxy. Threading dislocations with Burgers vectors of 1/3〈1120〉, 1/3〈1123〉 and [0001] were observed with a predominance of the first type. Additionally, inversion domains with Ga-polarity existed with respect to the adjacent matrix, which was of N-polarity. The dislocation densities and coherence lengths were deduced from x-ray diffraction and found to be in accordance with those measured by transmission electron microscopy. Both displacement fringe contrast analysis and high-resolution transmission electron microscopy results indicated that the inversion domain boundaries had Ga–N bonds between domains and the adjacent matrix.

Microstructural investigations on GaN films grown on SiC and sapphire substrates by laser induced molecular beam epitaxy have been performed. Threading dislocations with Burgers vectors of 1/3<1120>, 1/3<1123> and [0001] are typical line defects, predominantly the first type of dislocations. Their densities are typically 1.5×1010 cm−2 and 4×109 cm−2 on SiC and sapphire, respectively. Additionally, planar defects characterized as inversion domain boundaries lying on {1100} planes have been observed in GaN/sapphire samples with an inversion domain density of 4×109 cm−2. The inversion domains are of Ga-polarity with respect to the N-polarity of the adjacent matrix. However, GaN layers grown on SiC show Ga-polarity. Possible reasons for the different morphologies and structures of the films grown on different substrates are discussed. Based on an analysis of displacement fringes of inversion domains, an atomic model of the IDB-II with Ga-N bonds across the boundary was deduced. High resolution transmission electron microscopy (HRTEM) observations and the corresponding simulations confirmed the IDB-II structure determined by the analysis of displacement fringes.

La1-xCaxMnO3-δ (LCMO) thin films are grown by pulsed laser deposition on a (100) SrTiO3 substrate at temperatures between 530°C and 890°C. The magnetotransport properties show a high negative magnetoresistance and a shift of the maximum of the R(T) curve as function of temperature. The Curie temperature changes with deposition temperature and film quality in the range of 100-220K. The film quality is characterised by X-ray diffraction and transmission electron microscopy (TEM); film and target compositions were verified by atomic emission spectroscopy. The local structure of the film depends on the growth conditions and substrate temperature. TEM reveals a slight distortion of the film leading to a breakdown of the symmetry from orthorhombic to monoclinic. At the highest growth temperatures, a well defined interface is observed within the LCMO film, parallel to the substrate surface; this interface divides the film into two lamellae with a different microstructure. The lamella close to the substrate is perfectly coherent with the substrate, suggesting that it is strained as a result of the lattice parameter mismatch; the upper lamella shows a typical domain structure with unusual translation interfaces characterised by a displacement vector of the type 1/2 [010]m and 1/2[001]m when referred to the monoclinic lattice.

Fifty layers of carbon-induced germanium dots, separated by 9.6 nm Si, are stacked by solid source molecular beam epitaxy. Each dot layer consists of 0.2 monolayers of pre-deposited carbon and 2.4 monolayers of post-grown Ge. These carbon-induced germanium dots are only 10 to 15 nm in diameter and 1 to 2 nm in height. Vertical alignment due to penetrating strain fields of underlying dot layers is not observed. Unlike to an identical structure without the pre-growth of carbon, a variety of advantageous aspects such as strain compensation, strongly enhanced no-phonon photoluminescence at a wavelength of around 1.3 μm and the possibility of effective waveguiding make this stack of C-induced Ge islands an attractive structure for Si based optoelectronic devices.

Defect-free coalescence of Si layers which grow laterally over partially oxidized Si substrates is achieved in liquid phase epitaxy from indium solution. An adequate design of the oxide pattern on (111) substrates ascertains that the growth fronts of the Si layers merge gradually on the SiO2 and avoids the formation of inclusions or crystallographic defects. Electron Microscopy in diffraction contrast and convergent beam electron diffraction reveal that the epitaxial Si layers bend towards the substrate as they grow laterally over the SiO2 film. The layers straighten out again as they merge and form a perfect seam of coalescence.

A young girl with objective tinnitus is presented. Using tympanic membrane displacement, the probable origin of the tinnitus has been demonstrated. The patient has responded well to treatment with a tinnitus masker.

The microstructure of beam recrystallized silicon-on-insulator (SOI) films is strongly dependent on nucleation and growth processes during zone-melt propagation. In general, the recrystallization takes place along the (100) plane and in the <001> direction and in this case subgrain boundaries form the only major defects in the material. We have, however, identified stable growth regimes that produce predominantly twin boundaries, when the SOl films recrystallize with their surface parallel to the (110) planes. The twin formation process is attributed to growth twinning characteristic for f.c.c. and diamond structures. It has been established that the majority of these boundaries consist of coherent twins. In this manner (110) textured SOl films can be grown which contain almost entirely twin boundaries as structural defects. The crystallography of coherent twin boundaries in SOI films and their dependence on growth parameters is presented.

The fabrication of silicon-on-insulator structures was examined utilizing epitaxial growth of Si films on porous silicon and subsequent enhanced oxidation of the porous substrate. Porous silicon films have been formed by local anodic dissolution of silicon wafers in HF, while retaining the single crystalline structure. Low temperature liquid phase epitaxy (LPE) from saturated Ga solutions as well as molecular beam epitaxy (MBE) and laser induced epitaxy have been studied. Transmission electron microscopy (TEM) has demonstrated that all three techniques can achieve crystalline Si film growth on porous silicon. Surface smoothness and crystal perfection of the resulting epitaxial layers varies considerably with each technique.

The microstructure of high-quality recrystallized Si films on SiO2 substrates produced by CO2 laser induced zone-melting has been investigated by high voltage electron microscopy (HVEM). Subgrain boundaries represent the major defects in these recrystallized films. The origin of the subboundaries has been traced to periodic internal stress concentrations occurring at the faceted growth interface. These highly localized stresses cause plastic deformation of the growing single crystal film by nucleation of an array of slip dislocations. The mechanism responsible for the formation of subgrain boundaries has been revealed to be polygonization, where thermally activated dislocations rearrange themselves into the lower energy configuration of the low angle grain boundary.

Picosecond laser pulse irradiation of single crystalline Si can produce severe damage, including amorphisation. Morphology changes are studied by means of optical and high-voltage-electron microscopy and are found to depend on energy fluence, surface orientation, and wavelength. The detailed analysis of the damage distributions and thresholds lead to the conclusion, that energy-confinement precedes the introduction of structural changes, which are formed by rapid quenching from the liquid state.

The EBIC mode of the SEM has been used to investigate the perfection of cw CO2 laser annealed Si. Even in material that contains no slip lines, non-uniform charge collection is found. A combined X-ray and electron microscopy (TEM, SEM) study identified the residual defects responsible for the EBIC contrast as interstitial submicron dislocation loops. Scanning cw laser annealing independent of the wavelength (10.6μm or 0.514μm) always introduces residual defects which act as recombination centers and reduce minority carrier lifetime.

We have used cross-section TEM and Nomarski optical microscopy to examine the origin of halo patterns previously observed following picosecond irradiation of ion implantation amorphized Si. The importance of melt depth, quench rate and the incomplete nature of the initial amorphization step are emphasized. A search for a post annealing morphological or microstructural signature related to a plasma activated process proved negative.

Optical, X-ray and transmission electron microscopy plus preferential chemical etching have been used to examine the dislocations and lattice strain introduced during cw laser annealing of silicon. In addition to a substrate scanning mode we operate our cw Ar-ion laser in a “pulse” mode by using an electronically activated shutter located within the laser cavity. This permits accurate measurements to be made on isolated spots or large area scans with a dislocation density that can be deliberately varied. In particular we discuss surface slip traces, their component dislocations and resulting lattice strains, as well as submicron extrinsic dislocation loops which result from the condensation of ion-implantation produced interstitial silicon. Recommendations are presented for producing defect and strain-free material, as well as samples with specific densities of dislocations.