Near-infrared lasers are important for optical data communication, spectroscopy and medical diagnosis. Semiconductor nanowires offer the possibility of reducing the footprint of devices for ...three-dimensional device integration and hence are being extensively studied in the context of optoelectronic devices. Although visible and ultraviolet nanowire lasers have been demonstrated widely, progress towards room-temperature infrared nanowire lasers has been limited because of material quality issues and Auger recombination. (Al)GaAs is an important material system for infrared lasers that is extensively used for conventional lasers. GaAs has a very large surface recombination velocity, which is a serious issue for nanowire devices because of their large surface-to-volume ratio. Here, we demonstrate room-temperature lasing in core-shell-cap GaAs/AlGaAs/GaAs nanowires by properly designing the Fabry-Perot cavity, optimizing the material quality and minimizing surface recombination. Our demonstration is a major step towards incorporating (Al)GaAs nanowire lasers into the design of nanoscale optoelectronic devices operating at near-infrared wavelengths.
Significance We use transient spectroscopy to investigate the mechanism of singlet exciton fission, a quantum mechanical phenomenon in some organic molecules in which a spin-singlet excited state can ...split into two spin-triplet states. This process may be harnessed to boost solar cell efficiencies, but the underlying mechanism remains poorly understood. Central to most models is a triplet pair state, consisting of two triplets entangled into an overall spin-singlet configuration, but it has never before been optically detected. In a solution-based system, we detect a state with simultaneous singlet and triplet exciton character that dissociates to form triplet excitons in 120% yield. We consider that this intermediate constitutes a triplet pair state, and its observation allows important insight into the nature of triplet exciton coupling.
Singlet exciton fission is the spin-conserving transformation of one spin-singlet exciton into two spin-triplet excitons. This exciton multiplication mechanism offers an attractive route to solar cells that circumvent the single-junction ShockleyâQueisser limit. Most theoretical descriptions of singlet fission invoke an intermediate state of a pair of spin-triplet excitons coupled into an overall spin-singlet configuration, but such a state has never been optically observed. In solution, we show that the dynamics of fission are diffusion limited and enable the isolation of an intermediate species. In concentrated solutions of bis(triisopropylsilylethynyl)TIPSâtetracene we find rapid (<100 ps) formation of excimers and a slower (â¼10 ns) break up of the excimer to two triplet exciton-bearing free molecules. These excimers are spectroscopically distinct from singlet and triplet excitons, yet possess both singlet and triplet characteristics, enabling identification as a triplet pair state. We find that this triplet pair state is significantly stabilized relative to free triplet excitons, and that it plays a critical role in the efficient endothermic singlet fission process.
The events following Lehman's failure in 2008 and the current turmoil emanating from Europe highlight the structural vulnerabilities of short-term credit markets and the role of central banks as ...back-stop liquidity providers. The Federal Reserve's response to financial disruptions in the United States importantly included the creation of liquidity facilities. Using a differences-in-differences approach, we evaluate one of the most unusual of these interventions—the Asset-Backed Commercial Paper Money Market Mutual Fund Liquidity Facility. We find that this facility helped stabilize asset outflows from money market funds and reduced asset-backed commercial paper yields significantly.
The Family Law Act 1975 (Cth) provides that judges must not alter property rights on the breakdown of the relationship unless satisfied that it is just and equitable to do so. This is the principle ...of judicial restraint. In the past, and prior to the 2012 decision of the High Court in Stanford v Stanford, this principle was given almost no effect. The High Court sought to correct this approach, insisting that the family courts should not begin from an assumption that a couple’s property rights are or should be different from the state of the legal and equitable title. It also reaffirmed that there is no community of property in Australia. This article considers the significance of the principle of judicial restraint: first, in cases where the property is already jointly owned and, secondly, in cases where the couple have chosen to keep their finances separate.
Optoelectronic micro- and nanostructures have a vast parameter space to explore for modification and optimization of their functional performance. This paper reports on a data-led approach using ...high-throughput single nanostructure spectroscopy to probe >8000 structures, allowing for holistic analysis of multiple material and optoelectronic parameters with statistical confidence. The methodology is applied to surface-guided CsPbBr3 nanowires, which have complex and interrelated geometric, structural, and electronic properties. Photoluminescence-based measurements, studying both the surface and embedded interfaces, exploits the natural inter nanowire geometric variation to show that increasing the nanowire width reduces the optical bandgap, increases the recombination rate in the nanowire bulk, and reduces the rate at the surface interface. A model of carrier recombination and diffusion ascribes these trends to carrier density and strain effects at the interfaces and self-consistently retrieves values for carrier mobility, trap densities, bandgap, diffusion length, and internal quantum efficiency. The model predicts parameter trends, such as the variation of internal quantum efficiency with width, which is confirmed by experimental verification. As this approach requires minimal a priori information, it is widely applicable to nano- and microscale materials.
Tricked into marriage Parkinson, Patrick
Melbourne University law review,
01/2018, Letnik:
42, Številka:
1
Journal Article
Recenzirano
Many people, in recent years, have sought a decree of nullity on the basis that they have been tricked into marriage by fraudulent misrepresentations. These applications have routinely failed because ...the Family Court, applying ancient principles of canon law, has held that fraud is only relevant if it goes to the nature of the ceremony or the identity of the person, and not the motivation for entering the marriage. This article argues that many of these cases are wrongly decided. They have been treated as if they are all governed by the same principles, when important distinctions need to be made between different categories of case. The courts have failed to apply standard principles of statutory interpretation to the 'Marriage Act 1961' (Cth). Furthermore, the view that fraudulent misrepresentations can never provide the basis for a decree of nullity needs to be reconsidered as a consequence of the enactment of the 'Crimes Legislation Amendment (Slavery, Slavery-Like Conditions and People Trafficking) Act 2013' (Cth). Parliament has now made it a criminal offence to force someone into marriage, and the definition of forced marriage includes deception. If such deception is treated as negating consent, it would be anomalous to hold that the marriage remains valid.
Establishment of family relationships centres (FRCs) in Australia following reforms to the family law system - provision of information and advice and offering mediation for separated parents - how ...FRCs operate - what other jurisdictions can learn from Australia.
Spectroscopy and imaging in the terahertz (THz) region of the electromagnetic spectrum has proven to provide important insights in fields as diverse as chemical analysis, materials characterization, ...security screening, and nondestructive testing. However, compact optoelectronics suited to the most powerful terahertz technique, time-domain spectroscopy, are lacking. Here, we implement single GaAs nanowires as microscopic coherent THz sensors and for the first time incorporated them into the pulsed time-domain technique. We also demonstrate the functionality of the single nanowire THz detector as a spectrometer by using it to measure the transmission spectrum of a 290 GHz low pass filter. Thus, nanowires are shown to be well suited for THz device applications and hold particular promise as near-field THz sensors.
There are few areas of public policy in the Western world where there is as much turbulence as in family law. Often the disputes are seen in terms of an endless war between the genders. Reviewing ...developments over the last 30 years in North America, Europe and Australasia, Patrick Parkinson argues that, rather than just being about gender, the conflicts in family law derive from the breakdown of the model on which divorce reform was predicated in the late 1960s and early 1970s. Experience has shown that although marriage may be freely dissoluble, parenthood is not. Dealing with the most difficult issues in family law, this book charts a path for law reform that recognizes that the family endures despite the separation of parents, while allowing room for people to make a fresh start and prioritizing the safety of all concerned when making decisions about parenting after separation.
We have used transient terahertz photoconductivity measurements to assess the efficacy of two-temperature growth and core−shell encapsulation techniques on the electronic properties of GaAs ...nanowires. We demonstrate that two-temperature growth of the GaAs core leads to an almost doubling in charge-carrier mobility and a tripling of carrier lifetime. In addition, overcoating the GaAs core with a larger-bandgap material is shown to reduce the density of surface traps by 82%, thereby enhancing the charge conductivity.
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