CAREER IDENTITY AND MENTORING IN FIRST YEAR PHYSICS UNDERGRADUATES

The purpose of this study is to design and evaluate the effectiveness of a mentoring program run for first year physics students. The mentoring program was initiated to address the low student retention in undergraduate physics courses. Preliminary surveys found a mismatch between student career identity and perceived relevance of physics. Mentoring has been shown to have a positive effect on mentees’ science identity, retention, and career planning by promoting science outcomes for the mentees and positive attitudes about science. This has been particularly effective for students belonging to underrepresented groups in science, who typically have lower science identity. Students became acquainted with the 20-member mentoring panel in a flash mentoring event. Mentors were partnered with two students and asked to spend an average of fifteen minutes per week in discussion with the students. Discussion topics were emailed weekly. Some of our learnings from this pilot program included doing a post questionnaire during class time to ensure a high completion rate. The main gains cited by mentees were increased motivation to study, new vision of future career and employment and an increase in the number of career relevant skills they would learn through their course

Versatile method for template-free synthesis of single crystalline metal and metal alloy nanowires

© 2016 The Royal Society of Chemistry. Metal and metal alloy nanowires have applications ranging from spintronics to drug delivery, but high quality, high density single crystalline materials have been surprisingly difficult to fabricate. Here we report a versatile, template-free, self-assembly method for fabrication of single crystalline metal and metal alloy nanowires (Co, Ni, NiCo, CoFe, and NiFe) by reduction of metal nitride precursors formed in situ by reaction of metal salts with a nitrogen source. Thiol reduction of the metal nitrides to the metallic phase at 550-600 °C results in nanowire growth. In this process, sulfur acts as a uniaxial structure-directing agent, passivating the surface of the growing nanowires and preventing radial growth. The versatility of the method is demonstrated by achieving nanowire growth from gas-phase, solution-phase or a combination of gas- and solution-phase precursors. The fabrication method is suited to large-area CVD on a wide range of solid substrates

Robust multicolor single photon emission from point defects in hexagonal boron nitride

© 2017 IEEE. We demonstrates engineering of quantum emitters in hBN multi-layers using either electron beam irradiation or annealing. The defects exhibit a broad range of multicolor room-temperature single photon emissions across the visible and the near-infrared ranges

Photonic crystal cavities from hexagonal boron nitride

© 2018 The Author(s). Development of scalable quantum photonic technologies requires on-chip integration of photonic components. Recently, hexagonal boron nitride (hBN) has emerged as a promising platform, following reports of hyperbolic phonon-polaritons and optically stable, ultra-bright quantum emitters. However, exploitation of hBN in scalable, on-chip nanophotonic circuits and cavity quantum electrodynamics (QED) experiments requires robust techniques for the fabrication of high-quality optical resonators. In this letter, we design and engineer suspended photonic crystal cavities from hBN and demonstrate quality (Q) factors in excess of 2000. Subsequently, we show deterministic, iterative tuning of individual cavities by direct-write EBIE without significant degradation of the Q-factor. The demonstration of tunable cavities made from hBN is an unprecedented advance in nanophotonics based on van der Waals materials. Our results and hBN processing methods open up promising avenues for solid-state systems with applications in integrated quantum photonics, polaritonics and cavity QED experiments

Doped Beam Very Low Energy Particle Induced X-Ray Emission

University of Technology Sydney. Faculty of Science.Particle Induced X-Ray Emission (PIXE) is a spectroscopic technique where characteristic X-Rays are generated from a sample by the impact of high energy particles. PIXE is typically performed with protons in a particle accelerator at energies in excess of 1MeV and is used for the detection of trace elements due to the lower background compared to complementary techniques such as Scanning Electron Microscope (SEM) Energy Dispersive Spectroscopy (EDS). PIXE performed at energies of less than 1MeV is sometimes used to enhance sensitivity to light elements, however very low energy PIXE (VLE-PIXE) performed at energies available to a commercial focused ion beam microscope of ≤30keV was considered impossible due to the extremely low X-Ray production at these energies. In this research, VLE-PIXE was made possible by doping a hydrogen focused ion beam with a small proportion of a heavier ion species such as Ar or Xe. The characteristic X-Ray signal was shown to increase dramatically, allowing trace element analysis in the low parts per million range, offering performance comparable to proton only PIXE performed at much higher energies. This thesis outlines the implementation, characterisation, and application of the doped beam VLEPIXE technique in a commercial focused ion beam microscope utilising available hardware and little to no modification to the instrument. An investigation into the beam doping technique led to an interpretive model which considers various physical mechanisms which may be responsible for the increased performance which includes: the formation of quasi-molecules between the heavy projectile ion and the target atom, the suppression of non-radiative transitions, and vacancy lifetime modification due to multiple ionisation. These mechanisms may arise from the coincident impact of protons and a heavy ion species upon the same region of the sample. The ions backscattering from the surface during VLE-PIXE analysis were also analysed to provide additional information regarding the sample thickness and composition. This leads to the possibility of several new techniques such as simultaneous doped beam VLE-PIXE and backscattered ion spectroscopy for real-time tomography, or endpointing during Focused Ion Beam (FIB) milling

Influence of Bound versus Non-Bound Stabilizing Molecules on the Thermal Stability of Gold Nanoparticles

Knowledge concerning the sintering behavior of gold nanoparticles (AuNPs) allows for improved nanomaterials for applications such as printed electronics, catalysis and sensing. In this study, we examined the ability of a range of compounds to stabilize AuNPs against thermal sintering and compared compounds with and without functional groups that anchor the molecules to the nanoparticle surface. Thermal stability was characterized in terms of the temperature of the sintering event (<i>T</i>_SE) as well as thermogravimetric analysis and scanning electron microscopy. We show that anchored stabilizing compounds with high thermal stability are effective at preventing the sintering of AuNPs until the decomposition of the compound. A <i>T</i>_SE of 390 °C was achieved using 1-pyrenebutanethiol as stabilizer. Of the unanchored stabilizers, which were combined with butanethiol-capped AuNPs, two were found to be particularly effective: oleylamine (<i>T</i>_SE ≈ 300 °C) and a perylenedicarboximide derivative (<i>T</i>_SE ≈ 540 °C), the latter conferring an unprecedented level of thermal stability on ligand-stabilized AuNPs. When selecting stabilizers without anchoring groups, our results demonstrate the importance of choosing those that have an affinity with the capping ligands on the AuNPs to ensure a uniform mixture of AuNPs and stabilizer within a film

Ultra-bright emission from hexagonal boron nitride defects as a new platform for bio-imaging and bio-labelling

© 2016 SPIE. Bio-imaging requires robust ultra-bright probes without causing any toxicity to the cellular environment, maintain their stability and are chemically inert. In this work we present hexagonal boron nitride (hBN) nanoflakes which exhibit narrowband ultra-bright single photon emitters1. The emitters are optically stable at room temperature and under ambient environment. hBN has also been noted to be noncytotoxic and seen significant advances in functionalization with biomolecules2,3. We further demonstrate two methods of engineering this new range of extremely robust multicolour emitters across the visible and near infrared spectral ranges for large scale sensing and biolabeling applications