Transmission electron microscopy and Rutherford backscattering studies of different damage structures in P +

'Cross-sectional transmission electron microscopy (TEM)' and MeV He{sup +} channelling methods have been used to examine different damage structures present under the colour bands visible at the surface of a high dose rate P{sup +} implanted (111) Si implanted to a dose of 7.5 x 10{sup 15} ions/cm{sup 2}. TEM and channelling results obtained from individual coloured regions showed a good qualitative correlation in that discrete damage layers observed in the 'cross-sectional TEM' micrographs appeared as discrete peaks in the channelled spectra. The mean depths of the damage layers obtained from these two methods were in agreement. However, the widths of the deeper lying damage layers calculated from the channelling measurements were always greater than the widths observed by TEM. An emperical method based on subtraction of dechannelling background in the channelling spectra gave damage layer widths that were in close agreement with the TEM results

Activation of Al2O3 surface passivation of silicon : separating bulk and surface effects

Understanding surface passivation arising from aluminium oxide (Al2O3) films is of significant relevance for silicon-based solar cells and devices that require negligible surface recombination. This study aims to understand the competing bulk and surface lifetime effects which occur during the activation of atomic layer deposited Al2O3. We demonstrate that maximum passivation is achieved on n- and p-type silicon with activation at ∼ 450 °C, irrespective of annealing ambient. Upon stripping the Al2O3 films and re-passivating the surface using a superacid-based technique, we find the bulk lifetime of float-zone and Czochralski silicon wafers degrade at annealing temperatures > 450 °C. By accounting for this bulk lifetime degradation, we demonstrate that the chemical passivation component associated with Al2O3 remains stable at activation temperatures of 450─500 °C, achieving an SRV of 300 °C, the interface becomes Si/SixAlyO2/Al2O3 due to diffusion of aluminium into the thin silicon oxide layer

Electrically pumped continuous-wave III–V quantum dot lasers on silicon

Reliable, efficient electrically pumped silicon-based lasers would enable full integration of photonic and electronic circuits, but have previously only been realized by wafer bonding. Here, we demonstrate continuous-wave InAs/GaAs quantum dot lasers directly grown on silicon substrates with a low threshold current density of 62.5 A cm–2, a room-temperature output power exceeding 105 mW and operation up to 120 °C. Over 3,100 h of continuous-wave operating data have been collected, giving an extrapolated mean time to failure of over 100,158 h. The realization of high-performance quantum dot lasers on silicon is due to the achievement of a low density of threading dislocations on the order of 105 cm−2 in the III–V epilayers by combining a nucleation layer and dislocation filter layers with in situ thermal annealing. These results are a major advance towards reliable and cost-effective silicon-based photonic–electronic integration

Unification of New Zealand's local vertical datums: iterative gravimetric quasigeoid computations

New Zealand uses 13 separate local vertical datums (LVDs) based on normal-orthometric-corrected precise geodetic levelling from 12 different tide-gauges. We describe their unification using a regional gravimetric quasigeoid model and GPS-levelling data on each LVD. A novel application of iterative quasigeoid computation is used, where the LVD offsets computed from earlier models are used to apply additional gravity reductions from each LVD to that model. The solution converges after only three iterations yielding LVD offsets ranging from 0.24 m to 0.58 m with an average standard deviation of 0.08 m. The so-computed LVD offsets agree, within expected data errors, with geodetically levelled height differences at common benchmarks between adjacent LVDs. This shows that iterated quasigeoid models do have a role in vertical datum unification

Microsatellite and Mitochondrial Data Provide Evidence for a Single Major Introduction for the Neartic Leafhopper Scaphoideus titanus in Europe

Scaphoideus titanus, a leafhopper native to North America and invasive in Europe, is the vector of the Flavescence dorée phytoplasma, the causal agent of the most important form of grapevine yellows in European vineyards. We studied 10 polymorphic microsatellite loci and a 623 bp fragment of the mitochondrial cytochrome oxidase II gene in native S. titanus from north-eastern America and introduced European populations, to elucidate the colonization scenario. Consistent with their recent history, invasive European populations were less genetically diverse than American populations for both types of markers, suggesting a recent bottleneck. Significant isolation by distance was detected between American populations but not between European populations. None of the European mitochondrial haplotypes was found in the American vineyards, from which they are assumed to have originated. The precise source of the invasive S. titanus populations therefore remains unclear. Nevertheless, the high heterozygosity of North-East American populations (which contained 92% of the observed alleles) suggests that this region is part of the native range of S. titanus. Clustering population genetics analyses with microsatellite and mitochondrial data suggested that European populations originated from a single introduction event. Most of the introduced populations clustered with populations from Long Island, the Atlantic Coast winegrowing region in which Vitis aestivalis occurs

Listening to music reduces eye movements

Listening to music can change the way that people visually experience the environment, probably as a result of an inwardly directed shift of attention. We investigated whether this attentional shift can be demonstrated by reduced eye movement activity, and if so, whether that reduction depends on absorption. Participants listened to their preferred music, to unknown neutral music, or to no music while viewing a visual stimulus (a picture or a film clip). Preference and absorption were significantly higher for the preferred music than for the unknown music. Participants exhibited longer fixations, fewer saccades, and more blinks when they listened to music than when they sat in silence. However, no differences emerged between the preferred music condition and the neutral music condition. Thus, music significantly reduces eye movement activity, but an attentional shift from the outer to the inner world (i.e., to the emotions and memories evoked by the music) emerged as only one potential explanation. Other explanations, such as a shift of attention from visual to auditory input, are discussed

Evaluation of how active acoustic measurement can create a more intelligent process

I många processindustrier är det viktigt att kunna mäta processvätskors egenskaper på ett bra sätt. Detta går att göra på olika vis. Företaget Acosense AB producerar och säljer ett instrument för att analysera processvätskors egenskaper. Denna metod är en onlineanalys som baseras på aktiv akustisk spektroskopi. Onlineanalysen fungerar på så sätt att en ljudsignal med olika frekvenser skickas genom ett rör där processvätskan strömmar genom. På andra sidan röret sitter en sensor som registrerar ljudsignalen. Beroende på processvätskans egenskaper påverkas ljudsignalen olika mycket och på olika sätt. Det som mäts är hur ljudsignalen förändras. Vid Stora Enso Skutskär produceras pappers- och fluffmassa och anläggningen är en av de industrier som använder tekniken. Genom att i realtid mäta vissa egenskaper hos processvätskorna kan produktionen av massa effektiviseras. Examensarbetet går ut på att ta reda på hur bra tekniken fungerar för att analysera variablerna TOC(totalt organiskt kol), otvättad massakoncentration, tvättad massakoncentration och kappatal. Även en utvärdering av vilken nytta Stora Enso Skutskär kan ha av onlineanalysen görs. För att undersöka tekniken tas massaprover vid kokare 2 hos Stora Enso Skutskär. Proverna analyseras med avseende på de nämnda variablerna. Provresultaten kopplas sedan samman med akustiska spektrum som den akustiska mätutrustningen genererar. Tanken är att utvärdera om det går att analysera variablerna TOC, otvättad massakoncentration, tvättad massakoncentration och kappa med hjälp av akustiska spektrum och statistiska modelleringsmetoder. Denna sammankoppling görs med multivariat analys genom att skapa PCA- och PLS-modeller i programvaran SIMCA. Prover och akustiska spektrum som anses vara på något sätt fel eller icke representativt för massaprocessen eller den akustiska mätutrustningen utesluts för att inte påverka modellerna på ett negativt sätt. PLS-modellerna som tas fram för TOC, otvättad massakoncentration och tvättad massakoncentration har enligt SIMCA dåliga predikteringsförmågor. Även vid test med observationer som inte påverkar modellerna blir resultaten inte korrekta. Det få antalet observationer som modellerna bygger på tros vara en stor orsak till att modellernas predikteringsförmågor inte blir bra. Vid skapandet av PLS-modellen för kappa används betydligt fler observationer. Denna modells predikteringsförmåga blir bättre. För att kunna göra modellerna bättre föreslås att fler prover tas så att modellerna kan byggas upp av fler observationer. Genom att använda en fungerande akustisk onlineanalys går det troligen att effektivisera produktionen på fler än bara ett ställe vid Stora Enso Skutskär.In many process industries, it is important to be able to measure the properties of process fluids in a good way. This can be done in different ways. The company Acosense AB produces and sells an instrument that is able to analyze the properties of process fluids. This method is an online analysis based on active acoustic spectroscopy. The online analysis functions by sending an audio signal with different frequencies through a pipe where the process fluid flows through. At the other side of the pipe a sensor is located that registers the audio signal. Depending on the properties of the process fluids the audio signal is affected to a certain degree and in different ways. What is measured is how the audio signal changes. Stora Enso Skutskär where paper and fluff pulp is produced is one of the industries that use the technology. By measuring certain characteristics of the process fluid in real time the production of pulp can get more effective. The purpose of the thesis is to find out how well the technology is working to analyze the variables TOC (total organic carbon), unwashed pulp concentration, washed pulp concentration and kappa number. An evaluation of what benefits Stora Enso Skutskär may get from using the online analysis is also made. To investigate the technology pulp samples are taken at boiler 2 at Stora Enso Skutskär. The samples are analyzed with regard to the mentioned variables. The test results are then linked together to the acoustic spectrum that the acoustic measurement equipment generates. The idea is that it should possible to predict the variables TOC, unwashed pulp concentration, washed pulp concentration and kappa number by using only the acoustic spectrum and statistical modeling methods. This connection is made with multivariate analysis by creating PCA and PLS models in the software SIMCA. Samples and acoustic spectrum that are considered to stand out to much or are non-representative of the pulping process or of the acoustic measurement equipment are excluded so they don’t affect the models in a negative way. The PLS models are developed for TOC, unwashed pulp concentration and washed pulp concentration has, according to SIMCA poor ability to predict. When testing with the observations that do not affect the models, the results are still poor. The reason for the poor ability to predict is believed to be the low number of observations which the models are based on. When creating the PLS model for the kappa number a significantly higher number of observations are used. This models ability to predict is better.I In order to make better models it is suggested that more samples are taken so that the models can be based on more observations. By using a functional acoustic online analysis the production can probably get more efficient in more than one location at Stora Enso Skutskär

Structural dynamics of GaN microcrystals in evolutionary selection selective area growth probed by X-ray microdiffraction

A method to grow high quality, single crystalline semiconductor material irrespective of the substrate would allow a cost-effective improvement to functionality and performance of optoelectronic devices. Recently, a novel type of substrate-insensitive growth process called Evolutionary Selection Selective Area Growth (ES-SAG) has been proposed. Here we report the use of X-ray microdiffraction to study the structural properties of GaN microcrystals grown by ES-SAG. Utilizing high resolution in both direct and reciprocal spaces, we have unraveled structural dynamics of GaN microcrystals in growth structures of different dimensions. It has been found that the geometric proportions of the growth constrictions play an important role: 2.6â.Î 1/4m and 4.5â.Î 1/4m wide growth tunnels favor the evolutionary selection mechanism, contrary to the case of 8.6â.Î 1/4m growth tunnels. It was also found that GaN microcrystal ensembles are dominated by slight tensile strain irrespective of growth tunnel shape