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1.
Anal Chem ; 88(20): 10237-10244, 2016 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-27647382

RESUMO

Vicinal dithiol-containing proteins (VDPs) play a significant role in maintaining the cellular redox homeostasis and are implicated in many diseases. To provide new chemical tools for VDPs imaging, we report here a ratiometric fluorescent probe CAsH2 for VDPs using 7-diethylaminiocoumarin as the fluorescent reporter and cyclic 1,3,2-dithiarsenolane as the specific ligand. CAsH2 shows peculiar dual fluorescence emission from the excited intramolecular charge transfer (ICT) and twisted intramolecular charge transfer (TICT) states in aqueous media. However, upon selective binding of protein vicinal dithiols to the trivalent arsenical of CAsH2, the probe was brought from the polar water media into the hydrophobic protein domain, causing the excited state ICT to TICT conversion to be restricted; as a result, an increase from the ICT emission band and a decrease from the TICT emission band were observed simultaneously. The designed probe shows high selectivity toward VDPs over other proteins and biological thiols. Preliminary experiments show that CAsH2 can be used for the ratiometric imaging of endogenous VDPs in living cells. So far as we know, this is a rare example of the ratiometric fluorescent probe designed via modulating the ICT-TICT conversion process, which provides a new way to construct various protein-specific ratiometric fluorescent probes.


Assuntos
Aminocumarinas/química , Arsenicais/química , Corantes Fluorescentes/química , Proteínas/análise , Compostos de Sulfidrila/análise , Aminocumarinas/metabolismo , Aminocumarinas/efeitos da radiação , Animais , Arsenicais/metabolismo , Arsenicais/efeitos da radiação , Linhagem Celular Tumoral , Fluorescência , Corantes Fluorescentes/metabolismo , Corantes Fluorescentes/efeitos da radiação , Humanos , Luz , Camundongos , Microscopia Confocal , Microscopia de Fluorescência , Mitocôndrias/metabolismo , Proteínas/metabolismo , Compostos de Sulfidrila/metabolismo
2.
Chemosphere ; 150: 329-340, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26921586

RESUMO

Singlet and triplet potential energy surfaces for the atmospheric ozonation of trans-2-chlorovnyldichloroarsine (lewisite) are investigated theoretically. Optimizations of the reactants, products, intermediates and transition states are carried out at the BHandHLYP/6-311+G(d,p) level. Single point energy calculations are performed at the CCSD(T)/6-311+G(d,p) level based on the optimized structures. The detailed mechanism is presented and discussed. Various possible H (or Cl)-abstraction and C (or As)-addition/elimination pathways are considered. The results show that the As-addition/elimination is more energetically favorable than the other mechanisms. Rice-Ramsperger-Kassel-Marcus (RRKM) theory is used to compute the rate constants over the possible atmospheric temperature range of 200-3000 K and the pressure range of 10(-8)-10(9) Torr. The calculated rate constant is in good agreement with the available experimental data. The total rate coefficient shows positive temperature dependence and pressure independence. The modified three-parameter Arrhenius expressions for the total rate coefficient and individual rate coefficients are represented. Calculation results show that major product is CHClCHAs(OOO)Cl2 (s-IM3) at the temperature below 600 K and O2 + CHClCHAsOCl2 (s-P9) play an important role at the temperature between 600 and 3000 K. Time-dependent DFT (TD-DFT) calculations indicate that CHCl(OOO)CHAsCl2 (s-IM3) and CHOAsCl2 (s-P5) can take photolysis easily in the sunlight. Due to the absence of spectral information for arsenide, computational vibrational spectra of the important intermediates and products are also analyzed to provide valuable evidence for subsequent experimental identification.


Assuntos
Poluentes Atmosféricos/análise , Arsenicais/análise , Substâncias para a Guerra Química/análise , Modelos Teóricos , Ozônio/química , Poluentes Atmosféricos/química , Poluentes Atmosféricos/efeitos da radiação , Arsenicais/química , Arsenicais/efeitos da radiação , Substâncias para a Guerra Química/química , Substâncias para a Guerra Química/efeitos da radiação , Cinética , Fotólise , Pressão , Temperatura Ambiente
3.
Int J Pharm ; 478(1): 187-192, 2015 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-25448581

RESUMO

In this paper the stability of the arsenic sulfide (As4S4) nanosuspension prepared by wet milling in a circulation mill in the environment of copolymer Poloxamer 407 was studied. The obtained As4S4 particles in nanosuspension were of ∼ 100 nm in size. The influence of temperature and UV irradiation on the changes in physical and/or chemical properties was followed. Long-term stability was observed via particle size distribution and zeta potential measurements. Influence of UV irradiation was studied via UV-vis spectroscopy (UV-vis), photoluminicsence (PL) technique and Fourier transform infrared spectroscopy (FTIR) measurements. The best stability of the nanosuspension (24 weeks) was achieved when stored at 4°C and in the dark.


Assuntos
Arsenicais/química , Nanoestruturas/química , Sulfetos/química , Arsenicais/efeitos da radiação , Composição de Medicamentos/métodos , Estabilidade de Medicamentos , Nanoestruturas/efeitos da radiação , Tamanho da Partícula , Poloxâmero/química , Sulfetos/efeitos da radiação , Suspensões , Temperatura Ambiente , Raios Ultravioleta
4.
Nano Lett ; 14(1): 197-201, 2014 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-24341867

RESUMO

Plasmonics offers the opportunity of tailoring the interaction of light with single quantum emitters. However, the strong field localization of plasmons requires spatial fabrication accuracy far beyond what is required for other nanophotonic technologies. Furthermore, this accuracy has to be achieved across different fabrication processes to combine quantum emitters and plasmonics. We demonstrate a solution to this critical problem by controlled positioning of plasmonic nanoantennas with an accuracy of 11 nm next to single self-assembled GaAs semiconductor quantum dots, whose position can be determined with nanometer precision. These dots do not suffer from blinking or bleaching or from random orientation of the transition dipole moment as colloidal nanocrystals do. Our method introduces flexible fabrication of arbitrary nanostructures coupled to single-photon sources in a controllable and scalable fashion.


Assuntos
Arsenicais/química , Arsenicais/efeitos da radiação , Gálio/química , Gálio/efeitos da radiação , Nanopartículas/química , Nanopartículas/efeitos da radiação , Pontos Quânticos , Ressonância de Plasmônio de Superfície/instrumentação , Transdutores , Luz , Teste de Materiais , Nanopartículas/ultraestrutura , Tamanho da Partícula
5.
Opt Express ; 22(26): 32261-75, 2014 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-25607191

RESUMO

We report the cw-laser-induced oxidation of molecular-beam-epitaxy grown GaAsBi bismuth surface microdroplets investigated in situ by micro-Raman spectroscopy under ambient conditions as a function of irradiation power and time. Our results reveal the surface droplets are high-purity crystalline bismuth and the resultant Bi2O3 transformation to be ß-phase and stable at room temperature. A detailed Raman study of Bi microdroplet oxidation kinetics yields insights into the laser-induced oxidation process and offers useful real-time diagnostics. The temporal evolution of new ß-Bi2O3 Raman modes is shown to be well described by Johnson-Mehl-Avrami-Kolmogorov kinetic transformation theory and while this study limits itself to the laser-induced oxidation of GaAsBi bismuth surface droplets, the results will find application within the wider context of bismuth laser-induced oxidation and direct Raman laser processing.


Assuntos
Arsenicais/química , Bismuto/química , Cristalização/métodos , Gálio/química , Lasers , Análise Espectral Raman/métodos , Arsenicais/efeitos da radiação , Bismuto/efeitos da radiação , Gálio/efeitos da radiação , Teste de Materiais , Oxirredução/efeitos da radiação , Doses de Radiação , Soluções , Propriedades de Superfície/efeitos da radiação
6.
J Phys Condens Matter ; 25(41): 415301, 2013 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-24047679

RESUMO

We study the phonon-drag contribution to the thermoelectric power in a quasi-two-dimensional electron system confined in GaAs/AlGaAs heterostructure in the presence of both Rashba spin-orbit interaction and perpendicular magnetic field at very low temperature. It is observed that the peaks in the phonon-drag thermopower split into two when the Rashba spin-orbit coupling constant is strong. This splitting is a direct consequence of the Rashba spin-orbit interaction. We show the dependence of phonon-drag thermopower on both magnetic field and temperature numerically. A power-law dependence of phonon-drag magnetothermopower on the temperature in the Bloch-Gruneisen regime is found. We also extract the exponent of the temperature dependence of phonon-drag thermopower for different parameters like electron density, magnetic field, and the spin-orbit coupling constant.


Assuntos
Arsenicais/química , Elétrons , Transferência de Energia , Gálio/química , Campos Magnéticos , Modelos Químicos , Arsenicais/efeitos da radiação , Simulação por Computador , Transferência de Energia/efeitos da radiação , Gálio/efeitos da radiação , Temperatura Alta , Marcadores de Spin , Termodinâmica , Viscosidade/efeitos da radiação
7.
Opt Express ; 21(15): 18207-15, 2013 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-23938691

RESUMO

Multilayer anti-reflection (AR) coatings can be used to improve the efficiency of Gallium Arsenide (GaAs) solar cells. We propose an alternate method to obtain optical thin films with specified refractive indices, which is using a self-assembled nanoporous anodic aluminum oxide (AAO) template as an optical thin film whose effective refractive index can be tuned by pore-widening. Different kinds of double-layer AR coatings each containing an AAO layer were designed and investigated by finite difference time domain (FDTD) method. We demonstrate that a λ /4n - λ /4n AR coating consisting of a TiO(2) layer and an AAO layer whose effective refractive index is 1.32 realizes a 96.8% light absorption efficiency of the GaAs solar cell under AM1.5 solar spectrum (400 nm-860 nm). We also have concluded some design principles of the double-layer AR coating containing an AAO layer for GaAs solar cells.


Assuntos
Óxido de Alumínio/química , Arsenicais/química , Arsenicais/efeitos da radiação , Fontes de Energia Elétrica , Eletrodos , Gálio/química , Gálio/efeitos da radiação , Refratometria/instrumentação , Energia Solar , Adsorção , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Espalhamento de Radiação
8.
Opt Express ; 21(9): 11162-70, 2013 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-23669973

RESUMO

We demonstrate an integrated autocorrelator based on two superconducting single-photon detectors patterned on top of a GaAs ridge waveguide. This device enables the on-chip measurement of the second-order intensity correlation function g(2)(τ). A polarization-independent device quantum efficiency in the 1% range is reported, with a timing jitter of 88 ps at 1300 nm. g(2)(τ) measurements of continuous-wave and pulsed laser excitations are demonstrated with no measurable crosstalk within our measurement accuracy.


Assuntos
Arsenicais/química , Arsenicais/efeitos da radiação , Gálio/química , Gálio/efeitos da radiação , Fotometria/instrumentação , Ressonância de Plasmônio de Superfície/instrumentação , Condutividade Elétrica , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Estatística como Assunto , Integração de Sistemas
9.
Nanotechnology ; 24(21): 214006, 2013 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-23619012

RESUMO

We have performed a comparative study of ultrafast charge carrier dynamics in a range of III-V nanowires using optical pump-terahertz probe spectroscopy. This versatile technique allows measurement of important parameters for device applications, including carrier lifetimes, surface recombination velocities, carrier mobilities and donor doping levels. GaAs, InAs and InP nanowires of varying diameters were measured. For all samples, the electronic response was dominated by a pronounced surface plasmon mode. Of the three nanowire materials, InAs nanowires exhibited the highest electron mobilities of 6000 cm² V⁻¹ s⁻¹, which highlights their potential for high mobility applications, such as field effect transistors. InP nanowires exhibited the longest carrier lifetimes and the lowest surface recombination velocity of 170 cm s⁻¹. This very low surface recombination velocity makes InP nanowires suitable for applications where carrier lifetime is crucial, such as in photovoltaics. In contrast, the carrier lifetimes in GaAs nanowires were extremely short, of the order of picoseconds, due to the high surface recombination velocity, which was measured as 5.4 × 105 cm s⁻¹. These findings will assist in the choice of nanowires for different applications, and identify the challenges in producing nanowires suitable for future electronic and optoelectronic devices.


Assuntos
Arsenicais/química , Gálio/química , Índio/química , Nanofios/química , Nanofios/efeitos da radiação , Fosfinas/química , Semicondutores , Espectroscopia Terahertz/métodos , Arsenicais/efeitos da radiação , Condutividade Elétrica , Gálio/efeitos da radiação , Índio/efeitos da radiação , Teste de Materiais , Nanofios/ultraestrutura , Tamanho da Partícula , Fosfinas/efeitos da radiação , Doses de Radiação , Radiação Terahertz
10.
Nanotechnology ; 24(21): 214007, 2013 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-23619031

RESUMO

We present scalable large area terahertz (THz) emitters based on a nanoscale multilayer InGaAs/InAlAs heterostructure and a microstructured electrode pattern. The emitters are designed for pump lasers working at the telecommunication wavelength of 1.55 µm. Electric THz fields of more than 2.5 V cm⁻¹ are reached with moderate pump powers of 80 mW, the corresponding spectrum extends up to 3 THz. The saturation characteristics have been investigated for different pump laser spot sizes. For small pump powers of less than 50 mW the emitted THz field is nearly independent of the spot size, for higher pump powers and small spot sizes a clear saturation of the generated THz pulse can be observed. Hence the use of scalable emitters is especially promising for high power fibre laser systems. The spectral content of the generated radiation is nearly independent of the parameters spot size, pump power, and bias voltage, which allows for stable operation in spectroscopic applications.


Assuntos
Arsenicais/química , Gálio/química , Índio/química , Lasers , Iluminação/instrumentação , Nanopartículas/química , Nanotecnologia/instrumentação , Radiação Terahertz , Arsenicais/efeitos da radiação , Condutividade Elétrica , Desenho de Equipamento , Análise de Falha de Equipamento , Gálio/efeitos da radiação , Índio/efeitos da radiação , Teste de Materiais , Nanopartículas/efeitos da radiação , Nanopartículas/ultraestrutura , Propriedades de Superfície
11.
Nanotechnology ; 24(4): 045703, 2013 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-23299854

RESUMO

We investigate different processes for optimizing the formation of Ohmic contacts to InAs nanowires. The nanowires are grown via molecular beam epitaxy without the use of metal catalysts. Metallic contacts are attached to the nanowires by using an electron beam lithography process. Before deposition of the contacts, the InAs nanowires are treated either by wet etching in an ammonium polysulfide (NH(4))(2)S(x) solution or by an argon milling process in order to remove a surface oxide layer. Two-point electrical measurements show that the resistance of the ammonium polysulfide-treated nanowires is two orders of magnitude lower than that of the untreated nanowires. The nanowires that are treated by the argon milling process show a resistance which is more than an order of magnitude lower than that of those treated with ammonium polysulfide. Four-point measurements allow us to extract an upper bound of 1.4 × 10(-7) Ω cm(2) for the contact resistivity of metallic contacts on nanowires treated by the argon milling process.


Assuntos
Arsenicais/química , Eletrodos , Índio/química , Nanopartículas Metálicas/química , Arsenicais/efeitos da radiação , Condutividade Elétrica , Íons Pesados , Índio/efeitos da radiação , Teste de Materiais , Nanopartículas Metálicas/efeitos da radiação , Propriedades de Superfície/efeitos da radiação
12.
Opt Express ; 20(17): 19279-88, 2012 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-23038569

RESUMO

We report the first InGaAsP-based uni-travelling carrier photodiode structure grown by Solid Source Molecular Beam Epitaxy; the material contains layers of InGaAsP as thick as 300 nm and a 120 nm thick InGaAs absorber. Large area vertically illuminated test devices have been fabricated and characterised; the devices exhibited 0.1 A/W responsivity at 1550 nm, 12.5 GHz -3 dB bandwidth and -5.8 dBm output power at 10 GHz for a photocurrent of 4.8 mA. The use of Solid Source Molecular Beam Epitaxy enables the major issue associated with the unintentional diffusion of zinc in Metal Organic Vapour Phase Epitaxy to be overcome and gives the benefit of the superior control provided by MBE growth techniques without the costs and the risks of handling toxic gases of Gas Source Molecular Beam Epitaxy.


Assuntos
Arsenicais/química , Gálio/química , Índio/química , Fosfinas/química , Fotometria/instrumentação , Semicondutores , Arsenicais/efeitos da radiação , Cristalização/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Gálio/efeitos da radiação , Íons Pesados , Índio/efeitos da radiação , Teste de Materiais , Fosfinas/efeitos da radiação
13.
Opt Express ; 20(18): 19946-55, 2012 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-23037047

RESUMO

We demonstrate a regrowth-free material platform to create monolithic InGaAsP/InP photonic integrated circuits (PICs) with high-gain active and low-loss passive sections via a PL detuning of >135 nm. We show 2.5 µm wide by 400 µm long semiconductor optical amplifiers with >40 dB/mm gain at 1570 nm, and passive waveguide losses <2.3 dB/mm. The bandgap in the passive section is detuned using low-energy 190 keV channelized phosphorous implantation and subsequent rapid thermal annealing to achieve impurity-induced quantum well intermixing (QWI). The PL wavelengths in the active and passive sections are 1553 and 1417 nm, respectively. Lasing wavelengths for 500 µm Fabry-Perot lasers are 1567 and 1453 nm, respectively.


Assuntos
Arsenicais/química , Gálio/química , Índio/química , Fosfinas/química , Arsenicais/efeitos da radiação , Gálio/efeitos da radiação , Índio/efeitos da radiação , Íons , Teste de Materiais , Fosfinas/efeitos da radiação
14.
J Nanosci Nanotechnol ; 12(6): 5122-4, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22905589

RESUMO

The new technique combining metal-organic chemical vapor epitaxy with laser ablation of solid targets was used for fabrication of ferromagnetic GaAs structures with single Mn delta-doped layer. The structures demonstrated anomalous Hall effect, planar Hall effect, negative and anisotropic magnetoresistance in temperature range of 10-35 K. In GaAs structures with only single Mn delta-layer (without additional 2D hole gas channel or quantum well) ferromagnetism was observed for the first time.


Assuntos
Arsenicais/química , Arsenicais/efeitos da radiação , Gálio/química , Gálio/efeitos da radiação , Lasers , Manganês/química , Manganês/efeitos da radiação , Nanoestruturas/química , Nanoestruturas/efeitos da radiação , Campos Magnéticos , Teste de Materiais , Nanoestruturas/ultraestrutura , Tamanho da Partícula
15.
Nano Lett ; 12(9): 4943-7, 2012 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-22924961

RESUMO

Over the past decade, the properties of plasmonic waveguides have extensively been studied as key elements in important applications that include biosensors, optical communication systems, quantum plasmonics, plasmonic logic, and quantum-cascade lasers. Whereas their guiding properties are by now fairly well-understood, practical implementation in chipscale systems is hampered by the lack of convenient electrical excitation schemes. Recently, a variety of surface plasmon lasers have been realized, but they have not yet been waveguide-coupled. Planar incoherent plasmonic sources have recently been coupled to plasmonic guides but routing of plasmonic signals requires coupling to linear waveguides. Here, we present an experimental demonstration of electrically driven GaAs nanowire light sources integrated with plasmonic nanostrip waveguides with a physical cross-section of 0.08λ(2). The excitation and waveguiding of surface plasmon-polaritons (SPPs) is experimentally demonstrated and analyzed with the help of full-field electromagnetic simulations. Splitting and routing of the electrically generated SPP signals around 90° bends are also shown. The realization of integrated plasmon sources greatly increases the applicability range of plasmonic waveguides and routing elements.


Assuntos
Arsenicais/química , Arsenicais/efeitos da radiação , Gálio/química , Gálio/efeitos da radiação , Iluminação/métodos , Nanoestruturas/química , Nanoestruturas/efeitos da radiação , Ressonância de Plasmônio de Superfície/métodos , Campos Eletromagnéticos , Luz , Teste de Materiais , Nanoestruturas/ultraestrutura , Tamanho da Partícula
16.
Nanotechnology ; 23(9): 095602, 2012 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-22322330

RESUMO

Interesting phenomena during the Au-assisted chemical beam epitaxy of InAs-InSb nanowire heterostructures have been observed and interpreted within the framework of a theoretical model. An unusual, non-monotonous diameter dependence of the InSb nanowire growth rate is demonstrated experimentally within a range of deposition conditions. Such a behavior is explained by competition between the Gibbs-Thomson effect and different diffusion-induced material fluxes. Theoretical fits to the experimental data obtained at different flux pressures of In and Sb precursors allow us to deduce some important kinetic coefficients. Furthermore, we discuss why the InAs nanowire stem forms in the wurtzite phase while the upper InSb part has a pure zinc blende crystal structure. It is hypothesized that the 30° angular rotation of nanowire when passing from InAs to the InSb part is driven by the lowest surface energy of (1100) wurtzite and (110) zinc blende facets.


Assuntos
Arsenicais/química , Cristalização/métodos , Ouro/química , Índio/química , Modelos Químicos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/métodos , Arsenicais/efeitos da radiação , Simulação por Computador , Índio/efeitos da radiação , Substâncias Macromoleculares/química , Substâncias Macromoleculares/efeitos da radiação , Teste de Materiais , Modelos Moleculares , Conformação Molecular/efeitos da radiação , Nanoestruturas/efeitos da radiação , Tamanho da Partícula , Propriedades de Superfície/efeitos da radiação
17.
Environ Sci Technol ; 46(4): 2299-308, 2012 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-22225475

RESUMO

Heterogeneous photocatalytic reduction of As(V) and As(III) at different concentrations over TiO(2) under UV light in deoxygenated aqueous suspensions is described. For the first time, As(0) was unambiguously identified together with arsine (AsH(3)) as reaction products. As(V) reduction requires the presence of an electron donor (methanol in the present case) and takes place through the hydroxymethyl radical formed from methanol oxidation by holes or hydroxyl radicals. On the contrary, As(III) reduction takes place through direct reduction by the TiO(2)-conduction band electrons. Detailed mechanisms for the photocatalytic processes are proposed. Although reduction to solid As(0) is convenient for purposes of As removal from water as a deposit on TiO(2), attention must be paid to formation of AsH(3), one of the most toxic forms of As, and strategies for AsH(3) treatment should be considered.


Assuntos
Arsênico/química , Titânio/química , Poluentes Químicos da Água/química , Arsênico/efeitos da radiação , Arsenicais/química , Arsenicais/efeitos da radiação , Catálise , Oxirredução , Processos Fotoquímicos , Titânio/efeitos da radiação , Raios Ultravioleta , Poluentes Químicos da Água/efeitos da radiação
18.
Nano Lett ; 12(1): 252-8, 2012 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-22142481

RESUMO

The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited carriers, as well as to spatially control exciton recombination in GaAs-based nanowires (NWs) on a subns time scale. The experiments are carried out in core-shell NWs transferred to a SAW delay line on a LiNbO(3) crystal. Carriers generated in the NW by a focused laser spot are acoustically transferred to a second location, leading to the remote emission of subns light pulses synchronized with the SAW phase. The dynamics of the carrier transport, investigated using spatially and time-resolved photoluminescence, is well-reproduced by computer simulations. The high-frequency contactless manipulation of carriers by SAWs opens new perspectives for applications of NWs in opto-electronic devices operating at gigahertz frequencies. The potential of this approach is demonstrated by the realization of a high-frequency source of antibunched photons based on the acoustic transport of electrons and holes in (In,Ga)As NWs.


Assuntos
Arsenicais/química , Arsenicais/efeitos da radiação , Cristalização/métodos , Gálio/química , Gálio/efeitos da radiação , Nanoestruturas/química , Nanoestruturas/efeitos da radiação , Sonicação , Substâncias Macromoleculares/química , Substâncias Macromoleculares/efeitos da radiação , Teste de Materiais , Conformação Molecular/efeitos da radiação , Nanoestruturas/ultraestrutura , Tamanho da Partícula , Fótons , Propriedades de Superfície/efeitos da radiação
19.
Nano Lett ; 11(4): 1695-9, 2011 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-21446718

RESUMO

We present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong transverse electric field in the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed.


Assuntos
Arsenicais/química , Índio/química , Nanoestruturas/química , Fosfinas/química , Pontos Quânticos , Arsenicais/efeitos da radiação , Campos Eletromagnéticos , Elétrons , Índio/efeitos da radiação , Teste de Materiais , Nanoestruturas/efeitos da radiação , Tamanho da Partícula , Fosfinas/efeitos da radiação
20.
ACS Nano ; 5(3): 2191-9, 2011 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-21322642

RESUMO

We report a novel method for probing the gate-voltage dependence of the surface potential of individual semiconductor nanowires. The statistics of electronic occupation of a single defect on the surface of the nanowire, determined from a random telegraph signal, is used as a measure for the local potential. The method is demonstrated for the case of one or two switching defects in indium arsenide (InAs) nanowire field effect transistors at temperatures T=25-77 K. Comparison with a self-consistent model shows that surface potential variation is retarded in the conducting regime due to screening by surface states with density Dss≈10(12) cm(-2) eV(-1). Temperature-dependent dynamics of electron capture and emission producing the random telegraph signals are also analyzed, and multiphonon emission is identified as the process responsible for capture and emission of electrons from the surface traps. Two defects studied in detail had capture activation energies of EB≈50 meV and EB≈110 meV and cross sections of σ∞≈3×10(-19) cm2 and σ∞≈2×10(-17) cm2, respectively. A lattice relaxation energy of Sℏω=187±15 meV was found for the first defect.


Assuntos
Arsenicais/química , Índio/química , Nanoestruturas/química , Semicondutores , Processamento de Sinais Assistido por Computador/instrumentação , Arsenicais/efeitos da radiação , Campos Eletromagnéticos , Índio/efeitos da radiação , Teste de Materiais , Nanoestruturas/efeitos da radiação , Tamanho da Partícula
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