Search results for "ion recombination"

showing 3 items of 3 documents

Characterization of PTW-31015 PinPoint ionization chambers in photon and proton beams

2018

The increased use of complex forms of radiotherapy using small-field photon and proton beams has invoked a growing interest in the use of micro-ionization chambers. In this study, 48 PTW-TM31015 PinPoint-type micro-ionization chambers that are used in the commissioning and patient specific QA of a proton pencil beam scanning (PBS) delivery system have been characterized in proton and high-energy photon beams. In both beam modalities, the entire set of PinPoint chambers was characterized by imaging them, by evaluating their stability using check source measurements, by experimentally determining the ion recombination, polarity effect and by cross calibrating them in terms of absorbed dose to…

PhotonProton030218 nuclear medicine & medical imaging03 medical and health sciences0302 clinical medicineOpticscross-calibrationIonizationProton TherapyCalibrationHumansDosimetryRadiology Nuclear Medicine and imagingCobalt RadioisotopesRadiometryPencil-beam scanningpolarity effectPinPoint ionization chamberPhysicsPhotonsion recombinationRadiological and Ultrasound Technologybusiness.industryphoton030220 oncology & carcinogenesisCalibrationPhysics::Accelerator PhysicsProtonLaser beam qualityProtonsbusinessRelative Biological EffectivenessBeam (structure)Physics in Medicine & Biology
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Optical switching of quantum states inside self-assembled quantum dots

2008

Abstract Photoluminescence and excitation of photoluminescence spectroscopy have been performed for two kinds of single InAs self-assembled quantum dots grown on GaAs. The presence of unintentional impurities (donors and acceptors) offers the possibility to switch from negative to positively charged excitons by selectively exciting impurity related optical transitions.

Single QD spectroscopyPhotoluminescenceMaterials scienceCondensed matter physicsCondensed Matter::Otherbusiness.industryExcitonQuantum DotPhysics::OpticsCondensed Matter::Mesoscopic Systems and Quantum Hall EffectCondensed Matter PhysicsOptical switchCondensed Matter::Materials ScienceImpurityQuantum stateQuantum dotTrion recombinationOptoelectronicsGeneral Materials ScienceElectrical and Electronic EngineeringSpectroscopybusinessExcitation
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The origin of slow electron recombination processes in dye-sensitized solar cells with alumina barrier coatings

2004

We investigate the effect of a thin alumina coating of nanocrystalline TiO2 films on recombination dynamics of dye-sensitized solar cells. Both coated and uncoated cells were measured by a combination of techniques: transient absorption spectroscopy, electrochemical impedance spectroscopy, and open-circuit voltage decay. It is found that the alumina barrier reduces the recombination of photoinjected electrons to both dye cations and the oxidized redox couple. It is proposed that this observed retardation can be attributed primarily to two effects: almost complete passivation of surface trap states in TiO2 that are able to inject electrons to acceptor species, and slowing down by a factor of…

Solar cellsCharge injectionPassivationAbsorption spectroscopyIon recombinationThin filmsAluminaAnalytical chemistryGeneral Physics and AstronomyPhotochemistryTime resolved spectraTitanium compounds ; Alumina ; Nanostructured materials ; Semiconductor materials ; Thin films ; Solar cells ; Ion recombination ; Dyes ; Charge exchange ; Charge transfer states ; Charge injection ; Electrochemical impedance spectroscopy ; Time resolved spectraSemiconductor materials:FÍSICA [UNESCO]Ultrafast laser spectroscopyCharge exchangeThin filmSpectroscopyDyesQCChemistryUNESCO::FÍSICANanostructured materialsAcceptorDielectric spectroscopyDye-sensitized solar cellTACharge transfer statesTitanium compoundsElectrochemical impedance spectroscopy
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