We present the Sydney Radio Star Catalogue, a new catalogue of stars detected at megahertz to gigahertz radio frequencies. It consists of 839 unique stars with 3 405 radio detections, more than doubling the previously known number of radio stars. We have included stars from large area searches for radio stars found using circular polarisation searches, cross-matching, variability searches, and proper motion searches as well as presenting hundreds of newly detected stars from our search of Australian SKA Pathfinder observations. The focus of this first version of the catalogue is on objects detected in surveys using SKA precursor and pathfinder instruments; however, we will expand this scope in future versions. The 839 objects in the Sydney Radio Star Catalogue are distributed across the whole sky and range from ultracool dwarfs to Wolf-Rayet stars. We demonstrate that the radio luminosities of cool dwarfs are lower than the radio luminosities of more evolved sub-giant and giant stars. We use X-ray detections of 530 radio stars by the eROSITA soft X-ray instrument onboard the Spectrum Roentgen Gamma spacecraft to show that almost all of the radio stars in the catalogue are over-luminous in the radio, indicating that the majority of stars at these radio frequencies are coherent radio emitters. The Sydney Radio Star Catalogue can be found in Vizier or at https://radiostars.org.

The probability for amorphous silicon (a-Si) to phase transform under indentation testing is statistically determined as a function of annealing temperature from the probability of a pop-out event occurring on the unloading curve. Raman microspectroscopy is used to confirm that the presence of a pop-out event during indentation is a clear signature that a-Si undergoes phase transformation. The probability for such a phase transformation increases with annealing temperature and reaches 100% at a temperature of 340 °C, a temperature well before the temperature where the average bond-angle distortion is fully minimized. This suggests that multiple processes are occurring during full relaxation.

The indentation hardness of three different pure forms of silicon was investigated by two different methods. The hardness was probed by direct imaging of the residual impressions and by instrumented indentation using the Oliver–Pharr method. The forms of silicon used were a defective form of amorphous silicon, an amorphous form close to a continuous random network, and a crystalline silicon. The first form deforms via plastic flow and the latter two via phase transition. Two different unloading rates, fast and slow, were used to vary the phase transition behavior. This influenced the relative hardness as measured by instrumented indentation, which is not a reliable method to quantify hardness values in phase transforming materials. Thus, for our phase transforming silicon system, the relative hardness between samples can only be determined correctly by direct imaging, provided that the image accurately reveals the extent of the phase transformed volume.

A quantitative correlation between R-line luminescence at around 1.37 µm and {311} defect nature, size and concentration has been undertaken in silicon, following keV Si-implantation and subsequent annealing using photoluminescence spectroscopy and plan-view transmission electron microscopy. The formation and evolution of the rod-like defects were found to be dependent on annealing time at a temperature of 700 °C, but there was no simple correlation found between the density and size of those defects and the R-line intensity. In particular, whereas the presence of {311} defects is essential for observing R-line luminescence, both very small {311} defects at short annealing times and fully developed {311} defects at long annealing times do not contribute to such luminescence. We provide possible explanations for this behavior and suggest that the local (strain) environment around defects, the dopant level and impurities in the silicon substrate may all play a role in determining R-line intensity.

Archaeological work preceding a housing development revealed mid-Devensian (MIS 3) deposits preserved in a geological fault, a graben feature, on an interfluve plateau. Rare evidence for Early Upper Palaeolithic open-air occupation was characterised by a scant lithic signature of the Lincombian-Ranisian-Jerzmanowician (LRJ) leaf-point techno-complex of the North European plain. The lithics included a complete leaf-point, another broken example with traces of impact damage, and knapping debitage indicating leaf-point maintenance. The site also preserved good evidence for an open-air hyaena den with abundant faunal remains. Discrete bone clusters were present, some of which probably represent meat caches for hyaena cubs in the burrows and scrapes of a maternity den. It is suggested that the hominins targeted the den site to forage the stored food. Their occupation is associated with a group of spirally-fractured wild horse bones thought to be the result of marrow extraction by humans, and these have been dated to 44,290–42,440 calibrated years before present (44.3–42.5 kyr cal bp), comparable to the date range of continental LRJ sites. The early date of the LRJ techno-complex corresponds with that of the oldest Neanderthals in northern Europe, but possibly overlaps with the recently reported early dates for anatomically modern humans. However, it is concluded that the oldest Early Upper Palaeolithic technology in northern Europe was the product of final Neanderthals.

Nanoindentation-induced phase transformations in both crystalline silicon (c-Si) (100) and ion-implanted amorphous silicon have been studied at temperatures up to 200 °C. The region under the indenter undergoes rapid volume expansion at temperatures above 125 °C during unloading, which is indicated by “bowing” behavior in the load–displacement curve. Polycrystalline Si-I is the predominant end phase for indentation in crystalline silicon whereas high-pressure Si-III/Si-XII phases are the result of indentation in amorphous silicon. We suggest that the Si-II phase is unstable in a c-Si matrix at elevated temperatures and can directly transform to Si-I during the early stages of unloading.

A crystalline silicon surface, loaded by a Berkovich indenter to a constant maximum load, was unloaded using three unload functions, each consisting of five linear segments of equal time period. The first function had an exponentially decaying unload rate and was found to promote a pop-out event more readily than the second function, having a linear unload rate, or the third case with its unload rate increasing with time. Statistical analyses of experimental data suggest that the unload rate within 20%–30% of the maximum load, when the mean contact pressure in the indent volume is roughly 5 to 6 GPa, is the most dominant factor influencing the probabilistic occurrence of a pop-out event. Unload rates at higher load levels were shown to have a much less significant effect on the probability of pop-out occurrence.

Giant “pop-in” displacements are observed in crystalline silicon and germanium during high-load nanoindentation with a spherical diamond tip. These events are consistent with material removal triggered by lateral cracking during loading, which poses a hazard to microelectromechanical systems (MEMS) operation. We examine the scaling of the pop-in displacements as a function of peak indentation load and demonstrate a correlation with the depth of the plastic contact zone. We argue that giant pop-ins may occur in a broad range of highly brittle materials.

Detailed cyclic indentation experiments of crystalline silicon in this study show interesting behavior depending on the end phase from the previous cycle. To enable the behavior of these phases to be studied on reloading, the cyclic indentation response of the material is examined under conditions where the pressure-induced Si-II phase transforms either to amorphous (a-Si) or high pressure Si-XII/Si-III phases on unloading. For an amorphous end phase the subsequent reloading is hysteretic, and for high pressure crystalline end phases it is elastic. This indicates that, whereas a-Si re-transforms readily to Si-II upon reloading, Si-XII/Si-III does not retransform to Si-II even at the maximum indentation load. Based on the concept of the effective indenter shape and stresses induced in the material, we show that Si-XII/Si-III has a greater critical hydrostatic pressure for retransformation to Si-II than that of the diamond cubic Si-I.

An in situ electrical measurement technique for the investigation of nanoindentation using a Hysitron Triboindenter is described, together with details of experiments to address some technical issues associated with the technique. Pressure-induced phase transformations in silicon during indentation are of particular interest but are not fully understood. The current in situ electrical characterization method makes use of differences in electrical properties of the phase-transformed silicon to better understand the sequence of transformations that occur during loading and unloading. Here, electric current is measured through the sample/indenter tip during indentation, with a fixed or variable voltage applied to the sample. This method allows both current monitoring during indentation and the extraction of current-voltage (I-V) characteristics at various stages of loading. The work presented here focuses on experimental issues that must be understood for a full interpretation of results from nanoindentation experiments in silicon. The tip/sample contact and subsurface electrical resistivity changes dominate the resultant current measurement. Extracting the component of contact resistance provides an extremely sensitive method for measuring the electrical properties of the material immediately below the indenter tip, with initial results from indentation in silicon showing that this is a very sensitive probe of subsurface structural and electrical changes.

The crescent shaped Mascarene Plateau (south-western Indian Ocean), some 2200 km in length, forms a partial barrier to the (predominantly westward) flow of the South Equatorial Current. Shallow areas of the Mascarene Plateau effectively form a large shelf sea without an associated coastline. Zooplankton sampling transects were made across the plateau and also the basin to the west, to investigate the role the partial interruption of flow has on zooplankton biomass and community structure over the region. Biomass data from optical plankton counter (OPC) analysis, and variability in community structure from taxonomic analysis, appear to indicate that the obstruction by the plateau causes upwelling, nutrient enrichment and enhanced chlorophyll and secondary production levels downstream.  The Mascarene Basin is clearly distinguishable from the ridge itself, and from the waters to the south and north, both in terms of size-distributed zooplankton biomass and community structure. Satellite remote sensing data, particularly remotely-sensed ocean colour imagery and the sea surface height anomaly (SSHA), indicate support for this effect. A correlation was found between OPC biovolume and SSHA and sea surface temperature (SST), which may indicate the physical processes driving mesozooplankton variability in this area. Biomass values away from the influence of the ridge averaged 24 mg m−3, but downstream of the ridge biomass averaged 263 mg m−3. Copepods comprised 60% of the mean total organisms. Calanoid copepod numbers varied considerably between regions, being lowest away from the influence of the plateau, where higher numbers of the cyclopoid copepods Oithona spp., Corycaeus spp. and Oncaea spp., and the harpacticoid Microsetella spp. were found.

Details of the elastic–plastic transitions in crystalline compound semiconductors have been examined using spherical indentation. Two cubic (InP and GaAs) and two hexagonally structured semiconductors (ZnO and GaN) have been studied. A series of indentations have been made in each material at a number of different loads. The resulting load–penetration curves exhibited one or more discontinuities on loading (so called pop-in events). The load at which the initial pop-in event occurred has been measured along with the corresponding indenter extension. The elastic and elastic–plastic response of each material to spherical indentation has been calculated and compared with the experiment. By taking the difference between the elastic and elastic–plastic penetration depths, it has been found that the pop-in extension at each load could be predicted for each material. The detailed deformation behavior of each of the materials during indentation has also been discussed.

Deformation during spherical and pointed indentation in (100) crystalline silicon usig a UMIS-2000 nanoindenter has been studied using cross-sectional transmission electron microscopy (XTEM), atomic force microscopy (XTEM), atomic force microscopy and Raman microspectroscopy. XTEM samples were prepard by focused ion beam milling to accurately position the cross-section through the indentations. Indentation loads were chosen below an above the yield point for silicon to investigate the modes of plastic deformation. Slip planes are visible in XTEm micrographs for all indentation loads studied but slip is not the main avenue for plastic deformation. A thin layer of poly-crystalline material has been identified (indexed as Si-XII from diffraction patterns) on the low load indentation, just prior to yield (pop-in during loading). For loading above the yield point, a large region of amorphous silicon was observed directly under the indenter when fast unloading conditions were used. The various microstructures and phase observed below indentations are correlated with load/unload data.

The deformation behavior of as-grown and ion-beam-modified wurtzite GaN films is studied by a nanoindentation with a spherical indenter. Atomic force microscopy (AFM) and cathodoluminescence are used to characterize the deformation mode. No systematic dependence of the mechanical properties on the film thickness ( at least for thicknesses from 1.8 to 4 μm) as well as on doping type is observed. Results strongly suggest that (i) slip is the major contributor to the plastic deformatio of crystalline GaN and (ii) slip nucleation (rater than a phae transformation) is responsible for “pop-in” events observed during loading. Indentation with an ∼ 4.2 μm radius spherical indenter at maximum loads up to 900 mN does not produce any cracking visible by AFM in crystalline GaN. Instead, under such loads, indentation results in a pronounced elevation of the material around the impression. Implantation disorder dramatically changes the deformation behaviour of GaN. In particular, implanation-produced defects in crystalline GaN syppress (i) “pop-in” events during loading, (ii) slip bands observed by AFM, and (iii) the plastic component of deformation. GaN amorphized by in bombardment exhibits plastic flow even for very low loads. The values of hardness and elastic modulus of amorphous GaN are dramatically reduced compared to those of as-grown GaN.

The damage build-up and amorphization behavior in wurtzite GaN films under a wide range of implant conditions are studied by Rutherford backscattering / channeling spectrometry, transmission electron microscopy, and cathodoluminescence spectroscopy. A strong surface peak of lattice disorder, in addition to the expected damage peak in the region of the maximum of nuclear energy loss, has been observed for all implant conditions of this study. Capping of GaN with SiOx and SixNy layers prior to implantation does not eliminate surface disordering. This may suggest that nitrogen loss is not the main reason for the observed enhanced surface disorder, but, rather, the GaN surface acts as a strong sink for migrating point defects. However, pronounced loss of N during ion bombardment is observed for high dose implantation when the near-surface region is amorphized. Moreover, after amorphization, annealing at temperatures above about 400°C leads to complete decomposition of the near-surface layer.

Ion implantation can produce open volume defects in silicon by one of two methods, either by H or He implantation followed by annealing to create a band of nanocavities and also by direct implantation to reasonably high doses, which results in a vacancy excess region at depths less than about half the projected ion range. This paper reviews three interesting aspects of open volume defects. In the first case, the very efficient gettering of fast diffusing metals to nanocavities formed by H-implantation is illustrated. In addition, the non-equilibrium behaviour of Cu3Si precipitation and dissolution at cavities is examined. The second example treats the interaction of irradiation-induced defects with nanocavities, particularly preferential amorphisation at open volume defects and subsequent cavity shrinkage. The final example illustrates the coalescence of excess vacancies into small voids on annealing and the use of gettering of Au to detect such open volume defects.

We have investigated the high-pressure high-temperature annealing of Mg/P-implanted GaN films using visible and ultraviolet (UV) micro-Raman spectroscopy. The results illustrate the use of Raman spectroscopy to monitor processing of GaN where fast feedback is required. The structural quality and the stress in ion-implanted GaN films was monitored in a 40nm-thin surface layer of the sample as well as averaged over the sample layer thickness. We find the nearly full recovery of the crystalline quality of ion-implanted GaN films after annealing at 1400-1500°C under nitrogen overpressures of 1.5GPa. No significant degradation effects occurred in the GaN surface layer during the annealing. The high nitrogen overpressures proved very effective in preventing the nitrogen out-diffusion from the GaN surface. Stress introduced during the annealing was monitored. Raman spectra of ion-implanted GaN films were investigated at different temperatures and excitation wavelengths to study the GaN phonon density of states.

We have investigated the high-pressure high-temperature annealing of Mg/P-implanted GaN films using visible and ultraviolet (UV) micro-Raman spectroscopy. The results illustrate the use of Raman spectroscopy to monitor processing of GaN where fast feedback is required. The structural quality and the stress in ion-implanted GaN films was monitored in a 40nm-thin surface layer of the sample as well as averaged over the sample layer thickness. We find the nearly full recovery of the crystalline quality of ion-implanted GaN films after annealing at 1400-1500°C under nitrogen overpressures of 1.5GPa. No significant degradation effects occurred in the GaN surface layer during the annealing. The high nitrogen overpressures proved very effective in preventing the nitrogen out-diffusion from the GaN surface. Stress introduced during the annealing was monitored. Raman spectra of ion-implanted GaN films were investigated at different temperatures and excitation wavelengths to study the GaN phonon density of states.

We have recently reported the annealing and electrical properties of three new families (N1, N2 and N3) of vacancy complexes introduced in 1 keV He-, Ne- and Ar-ion bombarded nSi. In this paper we have employed deep level transient spectroscopy to investigate the ion mass, fluence and energy dependence of the introduction of N1 -defects. We observed an increase in the intensity of Ni -defects with increasing mass of bombarding ions for a fluence of 1×1012cm−2and flux of 1×1011cm−2s−1, which we have correlated with the mass dependence of nuclear energy deposition. The ratio of the intensities of Ni-defects to VO-center, [N1]/[VO], increased by ∼5 when bombarding with Ar- compared to He-ions. Increasing the Ar-ion fluence from 1×1012cm−2to l×1014cm−2for a flux of 5×1010 cm−2s−;1increased the intensity of N1-defects by ∼20 times, while [N1]/[VO] increased by a factor ∼2.3. N1-defects were not created by 5.4 MeV alpha-particle irradiation, but were present in varying relative concentrations in 1 to 150 keV He-ion bombarded n-Si.