Photonic crystal thin films of GaAs prepared by atomic layer deposition

Photonic crystal thin films were fabricated via the self-assembly of a lattice of silica spheres on silicon (100) substrates. Progressive infilling of the air spaces within the structure with GaAs was achieved using trimethylgallium and arsine under atomic-layer-deposition conditions. Samples with the highest levels of GaAs infill were subsequently inverted using selective etching. Reflectance spectra are interpreted via the Bragg expression and calculated photonic band structure diagrams. For GaAs infilled and inverted samples, the relative positions of the first and second order Bragg reflections are strongly influenced by the wavelength dependent refractive index

Electrical and physical characterization of the Al₂O₃/ <i>p</i>-GaSb interface for 1%, 5%, 10%, and 22% (NH₄)₂S surface treatments

In this work, the impact of ammonium sulfide ((NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;S) surface treatment on the electrical passivation of the Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/ &lt;i&gt;p&lt;/i&gt;-GaSb interface is studied for varying sulfide concentrations. Prior to atomic layer deposition of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, GaSb surfaces were treated in 1%, 5%, 10%, and 22% (NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;S solutions for 10 min at 295 K. The smallest stretch-out and flatband voltage shifts coupled with the largest capacitance swing, as indicated by capacitance-voltage (&lt;i&gt;CV&lt;/i&gt;) measurements, were obtained for the 1% treatment. The resulting interface defect trap density (&lt;i&gt;D&lt;/i&gt;&lt;sub&gt;it&lt;/sub&gt;) distribution showed a minimum value of 4 x 10&lt;sup&gt;12&lt;/sup&gt; cm&lt;sup&gt;-2&lt;/sup&gt;eV&lt;sup&gt;-1&lt;/sup&gt; at &lt;i&gt;E&lt;/i&gt;&lt;sub&gt;v&lt;/sub&gt; + 0.27 eV. Transmission electron microscopy and atomic force microscopy examination revealed the formation of interfacial layers and increased roughness at the Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/ &lt;i&gt;p&lt;/i&gt;-GaSb interface of samples treated with 10% and 22% (NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;S. In combination, these effects degrade the interface quality as reflected in the &lt;i&gt;CV&lt;/i&gt; characteristics

Longitudinal variation in O6-alkylguanine DNA-alkyltransferase activity in the human colon and rectum

In a systematic study of O6-alkylguanine DNA-alkyltransferase activity in the human colon and rectum, tumours were found to occur in regions of low activity. These results are consistent with the hypothesis that O6-alkylguanine DNA-alkyltransferase levels and alkylating agent exposure may be important determinants of large bowel tumorigenesis

On the front foot : Indigenous leadership in Aotearoa/New Zealand higher education

Despite increasing representation in higher education, Māori leaders are still seeking to overcome historical inequities and racial discrimination. This study investigates the circumstances of Māori leadership in higher education from a strength-based standpoint, highlighting the critical role Māori academics fulfil in senior leadership positions in Aotearoa/New Zealand universities by exploring Māori perceptions of the scope, influence and challenges of their senior leadership roles. These perceptions are described by five participants in the study and supported by literature predominantly authored by Māori academics. The qualitative study is underpinned by Political Race Theory, linking race and power at the individual level as well as at the institutional level. Findings give voice to senior leaders’ answers to the critical question: how can Indigenous leadership secure sustainable, transformative change in Aotearoa/New Zealand universities. The response to this question is underscored by the notion of shifting leadership positioning from the back-foot reactive politics to a front-foot status of strategic and transformative leadership. Reporting on Stage Five of an Australian project–Walan Mayiny: Indigenous Leadership in Higher Education, this study is the second in a series of three international case studies investigating Indigenous leadership in higher education

Inversion in the In0.53Ga0.47As metal-oxide-semiconductor system: Impact of the In0.53Ga0.47As doping concentration

In0.53Ga0.47As metal-oxide-semiconductor (MOS) capacitors with an Al2O3 gate oxide and a range of n and p-type In0.53Ga0.47As epitaxial concentrations were examined. Multi-frequency capacitance-voltage and conductance-voltage characterization exhibited minority carrier responses consistent with surface inversion. The measured minimum capacitance at high frequency (1 MHz) was in excellent agreement with the theoretical minimum capacitance calculated assuming an inverted surface. Minority carrier generation lifetimes, sg, extracted from experimentally measured transition frequencies, xm, using physics based a.c. simulations, demonstrated a reduction in sg with increasing epitaxial doping concentration. The frequency scaled conductance, G/x, in strong inversion allowed the estimation of accurate Cox values for these MOS devices

Paying-it-forward : Indigenous leadership in American higher education

This study focuses on Native American experiences of senior leadership in higher education, presenting a paradigm of Indigenous leadership based on the principle of paying-it-forward. The qualitative study, underpinned by Indigenist methodology, centers the responses of four Native American senior leaders in mainland America and Hawai´i who have strategically designed community-building policies and practices to counter ongoing isolation in higher education. Findings detail place-based leadership paradigms and practical strategies derived from Native American leadership rationales, showing the power of Native American leadership to challenge systemically biased perceptions, policies and practices that endeavor to isolate Indigenous peoples from each other, culture, language, and ways of being knowing and doing. The study is part of the international phase of an Australian-based project not only gives insight into higher education internationally, but also creates opportunity for consideration of what we can learn to our advantage in other colonized contexts