Homoepitaxial growth and characterization of 4H-SiC epilayers by low-pressure hot-wall chemical vapor deposition

Horizontal air-cooled low-pressure hot-wall CVD (LP-HWCVD) system is developed to get high quality 4H-SiC epilayers. Homoepitaxial growth of 4H-SiC on off-oriented Si-face (0001) 4H-SiC substrates purchased from Cree is performed at a typical temperature of 1500 degrees C with a pressure of 40 Torr by using SiH4+C2H4+H-2 gas system. The surface morphologies and structural and optical properties of 4H-SiC epilayers are characterized with Nomarski optical microscope, atomic force microscopy (AFM), x-ray diffraction, Raman scattering, and low temperature photoluminescence (LTPL). The background doping of 32 pm-thick sample has been reduced to 2-5 x 10(15) cm(-3). The FWHM of the rocking curve is 9-16 arcsec. Intentional N-doped and B-doped 4H-SiC epilayers are obtained by in-situ doping of NH3 and B2H6, respectively. Schottky barrier diodes with reverse blocking voltage of over 1000 V are achieved preliminarily.

Variation of Optical Quenching of Photoconductivity with Resistivity in Unintentional Doped GaN

The optical quenching of photoconductivity under dual illumination in GaN samples with different resistivity is investigated to reveal the variation of deep levels. The samples are grown by metal organic chemical vapour deposition without intentional doping. Quenching bands centered at 1.35 eV, 1.55 eV, 1.98 eV, and 2.60 eV are observed. It is found that the 1.98 eV quenching band is dominated in all the samples and the 2.60 eV band is observed only in the high-resistivity samples. The possible defect levels responsible for the quenching bands and the origin of different quenching behaviour at 2.60 eV are discussed. It is suggested that the defect level responsible for quenching at 2.60 eV plays an important role for the enhancement of resistivity.

Estudo do crescimento e caracterização de nanofitas do sistema ITO

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of edge dislocations and intentional Si doping on the electron mobility of n-type GaN films

The effects of dislocations and Si doping on the electrical properties of n-type GaN grown by metal organic chemical vapor deposition (MOCVD) are investigated. It is found that both electron mobility and carrier concentration are strongly influenced by edge dislocations. A moderate Si doping during the GaN growth improves the electron mobility, but the best doping effect depends on the dislocation density of the sample. High quality about 4-mu m-thick MOCVD-grown GaN film with a room temperature electron mobility as high as 1005 cm(2)/V s is obtained by optimizing growth conditions. (c) 2006 American Institute of Physics.

Safeguarding Rural Australia : Data Report No. 2 - Intentional Violence

This report focuses on our examination of extant data which have been sourced with respect to intentional violence perpetrated or experienced by males in regional and remote Australia. The nature of intentional violent acts can be physical, sexual or psychological or involve deprivation or neglect. We have presented under the headings of: self-harm including suicide; homicide; assault, sexual assault and the threat of assault; child abuse; other family and intimate partner violence; harassment, stalking and bullying; alcohol related social violence; and animal abuse. State variations in interpersonal violence are also presented. Additional commentary resulting from exploration, examination and analyses of secondary data is published online in complementary reports in this series.

Intentional first year curriculum design as a means of facilitating student engagement: some exemplars

The importance of student engagement to higher education quality, making deep learning outcomes possible for students, and achieving student retention, is increasingly being understood. The issue of student engagement in the first year of tertiary study is of particular significance. This paper takes the position that the first year curriculum, and the pedagogical principles that inform its design, are critical influencers of student engagement in the first year learning environment. We use an analysis of case studies prepared for Kift’s ALTC Senior Fellowship to demonstrate ways in which student engagement in the first year of tertiary study can be successfully supported through intentional curriculum design that motivates students to learn, provides a positive learning climate, and encourages students to be active in their learning.

Safeguarding rural Australia: addressing masculinity and violence in rural settings : intentional violent harm to others in an Australian rural context: analysis of secondary data analysis

This report is an update of an earlier one produced in January 2010 (see Carrington et al. 2010) which remains as an ePrint through the project’s home page. This report focuses on our examination of extant data which have been sourced with respect to intentional violence perpetrated or experienced by males living in regional and remote Australia . and which were available in public data bases at production. The nature of intentional violent acts can be physical, sexual or psychological or involve deprivation or neglect.

Community beliefs about intentional injury and responsibility for prevention

Community beliefs related to intentional injury inflicted by others were examined in a population-based telephone survey (n= 1032) in Queensland, Australia. Young adults 18-24 years were nominated as the most likely to be intentionally injured. 89.1% of respondents nominating this group believed that the injury incidents occur in alcohol environments. Though respondents from this age group also identified 18-24 yo as most likely to be intentionally injured, this was at a significantly lower level than did parents or 25-64 yo respondents. Responsibility for preventing injuries was placed on proprietors of licensed premises, schools and parents/family of the victim for alcohol, school and home environments respectively. Beliefs were aligned with prevalence data on intentional injury demonstrating a high level of awareness in the community about likely victims and situations where intentional injuries occur. Interventions could target families of young adults to capitalize on high levels of awareness about young adult vulnerability.

Developing a transition pedagogy : intentional curriculum design in first and final year law programs

This chapter will first consider the rationale for a transition pedagogy for first and final year law students. It then discusses the elements of a transition pedagogy for both years, noting the synergies and differences between programs designed to assist transition into and out of a law degree. In doing so, the authors attempt to explore the extent to which the first year curriculum principles identified by Sally Kift under an Australian Learning and Teaching Council (ALTC) Senior Fellowship may also be applied to the final year university experience. During the course of the discussion, examples are drawn from universities and Law Schools in Australia and internationally which seek to address these imperatives...

Enhancing photoactivity of TiO2(B)/anatase core-shell nanofibers by selectively doping cerium ions into the TiO2(B) Core

Cerium ions (Ce3+) can beselectively doped into the TiO2(B) core of TiO2(B)/anatase core–shell nanofibers by means of a simple one-pot hydrothermal treatment of a starting material of hydrogen trititanate (H2Ti3O7) nanofibers. These Ce3+ ions (≈0.202 nm) are located on the (110) lattice planes of the TiO2(B) core in tunnels (width≈0.297 nm). The introduction of Ce3+ ions reduces the defects of the TiO2(B) core by inhibiting the faster growth of (110) lattice planes. More importantly, the redox potential of the Ce3+/Ce4+ couple (E0(Ce3+/Ce4+)=1.715 V versus the normal hydrogen electrode) is more negative than the valence band of TiO2(B). Therefore, once the Ce3+-doped nanofibers are irradiated by UV light, the doped Ce3+ ions in close vicinity to the interface between the TiO2(B) core and anatase nanoshell can efficiently trap the photogenerated holes. This facilitates the migration of holes from the anatase shell and leaves more photogenerated electrons in the anatase nanoshell, which results in a highly efficient separation of photogenerated charges in the anatase nanoshell. Hence, this enhanced charge-separation mechanism accelerates dye degradation and alcohol oxidation processes. The one-pot treatment doping strategy is also used to selectively dope other metal ions with variable oxidation states such as Co2+/3+ and Cu+/2+ ions. The doping substantially improves the photocatalytic activity of the mixed-phase nanofibers. In contrast, the doping of ions with an invariable oxidation state, such as Zn2+, Ca2+, or Mg2+, does not enhance the photoactivity of the mixed-phase nanofibers as the ions could not trap the photogenerated holes.

Hybrid graphene/titania nanocomposite : interface charge transfer, hole doping, and sensitization for visible light response

We demonstrated for the first time by large-scale ab initio calculations that a graphene/titania interface in the ground electronic state forms a charge-transfer complex due to the large difference of work functions between graphene and titania, leading to substantial hole doping in graphene. Interestingly, electrons in the upper valence band can be directly excited from graphene to the conduction band, that is, the 3d orbitals of titania, under visible light irradiation. This should yield well-separated electron−hole pairs, with potentially high photocatalytic or photovoltaic performance in hybrid graphene and titania nanocomposites. Experimental wavelength-dependent photocurrent generation of the graphene/titania photoanode demonstrated noticeable visible light response and evidently verified our ab initio prediction.