P-n junctions formed in gallium antimonide

Vapor phase deposition process forms a heavily doped n-region on a melt-grown p-type gallium antimonide substrate. HCl transports gallium to the reaction zone, where it combines with antimony hydride and the dopant carrier, hydrogen telluride. Temperatures as low as 400 degrees C are required

Lamb wave near field enhancements for surface breaking defects in plates

Near field surface wave ultrasonic enhancements have previously been used to detect surface breaking defects in thick samples using Rayleigh waves. Here, we present analogous surface wave enhancements for Lamb waves propagating in plates. By tracking frequency intensities in selected regions of time-frequency representations, we observe frequency enhancement in the near field, due to constructive interference of the incident wave mode with those reflected and mode converted at the defect. This is explained using two test models; a square based notch and an opening crack, which are used to predict the contribution to the out-of-plane displacement from the reflected and mode converted waves. This method has the potential to provide a reliable method for the near field identification and characterisation of surface breaking defects in plates

Controlled substrate cooling improves reproducibility of vapor deposited semiconductor composites

Improved substrate holder preferentially provides more uniform substrate cooling and increases the proportion of vapor flowing over the substrate during growth. Nitrogen gas is constricted in the substrate holder to cool the substrate

Learning in the Panopticon: ethical and social issues in building a virtual educational environment

This paper examines ethical and social issues which have proved important when initiating and creating educational spaces within a virtual environment. It focuses on one project, identifying the key decisions made, the barriers to new practice encountered and the impact these had on the project. It demonstrates the importance of the ‘backstage’ ethical and social issues involved in the creation of a virtual education community and offers conclusions, and questions, which will inform future research and practice in this area. These ethical issues are considered using Knobel’s framework of front-end, in-process and back-end concerns, and include establishing social practices for the islands, allocating access rights, considering personal safety and supporting researchers appropriately within this contex

Growth of single-crystal gallium nitride

Use of ultrahigh purity ammonia prevents oxygen contamination of GaN during growth, making it possible to grow the GaN at temperatures as high as 825 degrees C, at which point single crystal wafers are deposited on /0001/-oriented sapphire surfaces

Vapor Phase Growth Technique and System for Several III-V Compound Semiconductors Interim Scientific Report

Vapor phase crystal growth and preparation of gallium, indium, arsenic, phosphorous, and antimony alloy semiconductor material

Vapor phase growth technique and system for several 3-5 compound semiconductors Quarterly technical report

Single vapor phase growth system for preparing semiconductor material

Alcohol, assault and licensed premises in inner-city areas

This report contains eight linked feasibility studies conducted in Cairns during 2010. These exploratory studies examine the complex challenges of compiling and sharing information about incidents of person-to-person violence in a late night entertainment precinct (LNEP). The challenges were methodological as well as logistical and ethical. The studies look at how information can be usefully shared, while preserving the confidentiality of those involved. They also examine how information can be compiled from routinely collected sources with little or no additional resources, and then shared by the agencies that are providing and using the information.Although the studies are linked, they are also stand-alone and so can be published in peer-reviewed literature. Some have already been published, or are ‘in press’ or have been submitted for review. Others require the NDLERF board’s permission to be published as they include data related more directly to policing, or they include information provided by police.The studies are incorporated into the document under section headings. In each section, they are introduced and then presented in their final draft form. The final published form of each paper, however, is likely to be different from the draft because of journal and reviewer requirements. The content, results and implications of each study are discussed in summaries included in each section.Funded by the National Drug Law Enforcement Research Fund, an initiative of the National Drug StrategyAlan R Clough (PhD) School of Public Health, Tropical Medicine and Rehabilitation Sciences James Cook UniversityCharmaine S Hayes-Jonkers (BPsy, BSocSci (Hon1)) James Cook University, Cairns.Edward S Pointing (BPsych) James Cook University, Cairns

Scanning laser source and scanning laser detection techniques for different surface crack geometries

Standard test samples typically contain simulated defects such as slots machined normal to the surface. However, real defects will not always propagate in this manner; for example, rolling contact fatigue on rails propagates at around 25º to the surface, and corrosion cracking can grow in a branched manner. Therefore, there is a need to understand how ultrasonic surface waves interact with different crack geometries. We present measurements of machined slots inclined at an angle to the surface normal, or with simple branched geometries, using laser ultrasound. Recently, Rayleigh wave enhancements observed when using the scanning laser source technique, where a generation laser is scanned along a sample, have been highlighted for their potential in detecting surface cracks. We show that the enhancement measured with laser detector scanning can give a more significant enhancement when different crack geometries are considered. We discuss the behaviour of an incident Rayleigh wave in the region of an angled defect, and consider mode-conversions which lead to a very large enhancement when the detector is close to the opening of a shallow defect. This process could be used in characterising defects, as well as being an excellent fingerprint of their presence

Non-contact ultrasonic detection of angled surface defects

Non-destructive testing is an important technique, and improvements are constantly needed. Surface defects in metals are not necessarily confined to orientations normal to the sample surface; however, much of the previous work investigating the interaction of ultrasonic surface waves with surface-breaking defects has assumed cracks inclined at 90° to the surface. This paper explores the interaction of Rayleigh waves with cracks which have a wide range of angles and depths relative to the surface, using a non-contact laser generation and detection system. Additional insight is acquired using a 3D model generated using finite element method software. A clear variation of the reflection and transmission coefficients with both crack angle and length is found, in both the out-of-plane and in-plane components. The 3D model is further used to understand the contributions of different wavemodes to B-Scans produced when scanning a sample, to enable understanding of the reflection and transmission behaviour, and help identify angled defects. Knowledge of these effects is essential to correctly gauge the severity of surface cracking