Photoconducting Properties of Ultraviolet Detectors Based on GaN and Al1-xGaxN Films Grown by ECR-MBE

1996 ◽  
Vol 449 ◽  
Author(s):  
M. Misra ◽  
D. Korakakis ◽  
R. Singh ◽  
A. Sampath ◽  
T. D. Moustakas
Keyword(s):  
Direct Measurement ◽  
Microwave Power ◽  
Response Times ◽  
Spectral Response ◽  
Alpha Particles ◽  
Detector Response ◽  
Photoconductive Gain ◽  
Ultraviolet Detectors ◽  
Transmission Measurements ◽  
First Time

ABSTRACTGaN and All-xGaxN films were grown by the method of ECR-MBE. Absorption constants as a function of wavelength were determined from transmission measurements. Photoconducting detectors were fabricated from these films and characterized in terms of their spectral response and photoconductive gain. Mobility-lifetime products were determined from the measurement of photoconductive gain. The resistivity and mobility-lifetime products of the films were varied from 10-109 ohm-cm and 10-3 -10-8 cm2/V respectively by changing the microwave power in the ECR discharge from 20-60 watts. The change in the mobility-lifetime product is attributed to change in the lifetimes of the photogenerated carriers. This assumption is supported by direct measurement of detector response times. Finally, we report for the first time, the detection of alpha particles using GaN detectors.

scholarly journals Solar-blind ultraviolet photodetector based on graphene/vertical Ga2O3 nanowire array heterojunction

Nanophotonics ◽  
2018 ◽  
Vol 7 (9) ◽  
pp. 1557-1562 ◽  
Author(s):  
Tao He ◽  
Yukun Zhao ◽  
Xiaodong Zhang ◽  
Wenkui Lin ◽  
Kai Fu ◽  
...  
Keyword(s):  
Response Times ◽  
Nanowire Array ◽  
Graphene Film ◽  
Fast Response ◽  
Nanowire Arrays ◽  
Monolayer Graphene ◽  
Ultraviolet Photodetector ◽  
Solar Blind ◽  
Decay Times ◽  
First Time

AbstractIn this paper, a solar-blind ultraviolet photodetector (PD) based on the graphene/vertical Ga2O3 nanowire array heterojunction was proposed and demonstrated. To the best of our knowledge, it is the first time that vertical Ga2O3 nanowire arrays have been realized. Ga2O3 nanowires were obtained by thermally oxidizing GaN nanowires grown by molecular beam epitaxy on n-doped Si substrate. Then, a monolayer graphene film was transferred to Ga2O3 nanowires to form the graphene/vertical Ga2O3 nanowire array heterojunction and transparent electrodes. The fabricated device exhibited a responsivity (R) of 0.185 A/W and rejection ratio (R258 nm/R365 nm) of 3×104 at the bias of −5 V. Moreover, the fast response times of this PD were 9 and 8 ms for the rise and decay times under 254 nm illumination, respectively, which are attributed to the unique properties of nanowire arrays and the graphene/vertical Ga2O3 nanowire array heterojunction structure.

scholarly journals From benzene to naphthalene: direct measurement of reactions and intermediates of phenyl radicals and acetylene

2019 ◽  
Vol 21 (40) ◽  
pp. 22248-22258 ◽  
Author(s):  
Te-Chun Chu ◽  
Zachary J. Buras ◽  
Mica C. Smith ◽  
Awele B. Uwagwu ◽  
William H. Green
Keyword(s):  
Time Evolution ◽  
Direct Measurement ◽  
Time Measurement ◽  
Phenyl Radicals ◽  
Dependent Model ◽  
First Time

First-time measurement of time evolution of the main products and critical intermediates on phenyl HACA pathways with a validated pressure-dependent model.

scholarly journals Sodium Alginate Cross-Linkable Planar 1D Photonic Crystals as a Promising Tool for Pb2+ Detection in Water

Chemosensors ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 37 ◽  
Author(s):  
Andrea Dodero ◽  
Paola Lova ◽  
Silvia Vicini ◽  
Maila Castellano ◽  
Davide Comoretto
Keyword(s):  
Refractive Index ◽  
Photonic Crystals ◽  
Sodium Alginate ◽  
Spectral Response ◽  
High Refractive Index ◽  
Polluted Water ◽  
Ionic Exchange ◽  
Promising Tool ◽  
Rural Environments ◽  
First Time

Due to its high toxicity, Pb2+ pollution is a serious threat for human health and environments. However, in situ real-time detection of Pb2+ pollution is difficult and laboratory instruments are usually required. Then, the possibility to monitor water quality without laboratory instruments could lead to the extensive assessment of polluted water sources, especially in rural environments and developing countries where large lead concentrations are often found in surface water. Consequently, new simple colorimetric sensors are highly interesting in the field. In this work we report for the first time disposable polymer planar 1D photonic crystals made of poly (N-vinylcarbazole) as high refractive index medium and sodium alginate as low refractive index and active medium for the detection of Pb2+ in water. The detection relies on the ionic exchange occurring into the alginate matrix. This process effectively induces a physical cross-linking phenomenon, which inhibits water solubilization of the polymer. In turn, this affects the spectral response of the planar 1D photonic crystals modifying its color.

Well-defined nickel(II) tetrazole-saccharinate complex as homogeneous catalyst on the reduction of aldehydes: scope and reaction mechanism

2020 ◽  
Vol 92 (1) ◽  
pp. 151-166 ◽  
Author(s):  
Luís M. T. Frija ◽  
Bruno G. M. Rocha ◽  
Maxim L. Kuznetsov ◽  
Lília I. L. Cabral ◽  
M. Lurdes S. Cristiano ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Transition Metal ◽  
Dft Calculations ◽  
Microwave Power ◽  
Low Temperatures ◽  
Nickel Complex ◽  
Transition Metal Catalysts ◽  
Homogeneous Catalyst ◽  
First Time

AbstractA new (tetrazole-saccharin)nickel complex is shown to be a valuable catalyst for the hydrosilative reduction of aldehydes under microwave radiation at low temperatures. With typical 1 mol% content of the catalyst (microwave power range of 5–15 W) most reactions are complete within 30 min. The Ni(II)-catalyzed reduction of aldehydes, with a useful scope, was established for the first time by using this catalyst, and is competitive with the most effective transition-metal catalysts known for such transformation. The catalyst reveals tolerance to different functional groups, is air and moisture stable, and is readily prepared in straightforward synthetic steps. Supported by experimental data and DFT calculations, a plausible reaction mechanism involving the new catalytic system is outlined.

High-accuracy X-ray absorption spectra from mMsolutions of nickel (II) complexes with multiple solutions using transmission XAS

2015 ◽  
Vol 22 (4) ◽  
pp. 1008-1021 ◽  
Author(s):  
Christopher T. Chantler ◽  
M. Tauhidul Islam ◽  
Stephen P. Best ◽  
Lachlan J. Tantau ◽  
Chanh Q. Tran ◽  
...  
Keyword(s):  
Multiple Solutions ◽  
High Accuracy ◽  
Hybrid Technique ◽  
Edge Structure ◽  
New Approach ◽  
X Ray ◽  
Square Planar ◽  
Transmission Measurements ◽  
First Time ◽  
X Ray Absorption

A new approach is introduced for determining X-ray absorption spectroscopy (XAS) spectra on absolute and relative scales using multiple solutions with different concentrations by the characterization and correction of experimental systematics. This hybrid technique is a development of standard X-ray absorption fine structure (XAFS) along the lines of the high-accuracy X-ray extended range technique (XERT) but with applicability to solutions, dilute systems and cold cell environments. This methodology has been applied to determining absolute XAS of bis(N-n-propyl-salicylaldiminato) nickel(II) and bis(N-i-propyl-salicylaldiminato) nickel(II) complexes with square planar and tetrahedral structures in 15 mMand 1.5 mMdilute solutions. It is demonstrated that transmission XAS from dilute systems can provide excellent X-ray absorption near-edge structure (XANES) and XAFS spectra, and that transmission measurements can provide accurate measurement of subtle differences including coordination geometries. For the first time, (transmission) XAS of the isomers have been determined from low-concentration solutions on an absolute scale with a 1–5% accuracy, and with relative precision of 0.1% to 0.2% in the active XANES and XAFS regions after inclusion of systematic corrections.

Measurements of Melting Velocities in Gold Films on a Picosecond Time Scale

1992 ◽  
Vol 279 ◽  
Author(s):  
B. E. Homan ◽  
M. T. Connery ◽  
D. E. Harrison ◽  
C. A. Macdonald
Keyword(s):  
Direct Measurement ◽  
Time Scale ◽  
Dye Laser ◽  
Gold Films ◽  
Interfacial Velocity ◽  
Pump Probe ◽  
Laser Probe ◽  
Picosecond Time Scale ◽  
Probe Transmission ◽  
Transmission Measurements

ABSTRACTMelting velocities were measured in thin gold films by performing pump/probe transmission measurements using a unique picosecond excimer pump and dye laser probe. Monitoring the depth of the liquid by changes in the near psuedo-Brewster's angle transmission allowed for direct measurement of crystal/melt interfacial velocity up to 1500 m/s.

Performance and Spectral Response of Far-Infrared Pb1−xSnxTe(In) Photodetectors

1999 ◽  
Vol 607 ◽  
Author(s):  
I. Ivanchik ◽  
D. Khokilov ◽  
J. Pipher ◽  
N. Raines ◽  
D. Watson
Keyword(s):  
State Of The Art ◽  
Spectral Response ◽  
Far Infrared ◽  
Integration Time ◽  
First Time

AbstractDirect comparison of performance has been done for a Pb1−xSnxTe(In) photodetector, a Si(Sb) BIB structure and a state of the art Ge(Ga) photoconductor in the integration cavity. The PblSnTe(In) photodetector shows several orders of magnitude higher responsivity S, then the Si(Sb) BIB at the wavelength λ ∼ 14 µm. Persistent photoresponse with SI ∼ 103 A/W at 40 mV bias and 1 s integration time at the wavelengths of, λ = 90 and 116 µm has been observed for the first time for the Pb1−xSnxTe(In) photodetector. This value is by a factor of ∼ 100 higher than the respective parameters of the Ge(Ga) photoconductor in the same conditions.

scholarly journals The spectral response of a phosphor to infra-red radiation

1949 ◽  
Vol 196 (1047) ◽  
pp. 554-562 ◽  
Keyword(s):  
Room Temperature ◽  
Spectral Response ◽  
Cadmium Sulphide ◽  
Air Temperatures ◽  
Infra Red ◽  
Zinc Cadmium ◽  
Temperature Radiation ◽  
First Time ◽  
Red Radiation

A determination of the infra-red spectral response of a copper-activated zinc cadmium sulphide phosphor at normal and at liquid air temperatures is described. Peaks in sensitivity at wave-lengths of 2·1 and 2·7 μ are observed directly for the first time and are correlated with glow-curve data. The incidence of room temperature radiation on a phosphor at liquid air temperature is shown to make the observation of sensitivity beyond 3 μ impracticable.

The Decay of 169Yb

1972 ◽  
Vol 50 (19) ◽  
pp. 2348-2354 ◽  
Author(s):  
S. K. Sen ◽  
D. L. Salie ◽  
E. Tomchuk
Keyword(s):  
Direct Measurement ◽  
Gamma Rays ◽  
Internal Conversion ◽  
Gamma Ray ◽  
Conversion Coefficient ◽  
Coulomb Excitation ◽  
Internal Conversion Coefficient ◽  
Electron Capture Decay ◽  
Upper Limits ◽  
First Time

The decay of 169Yb was investigated using several Ge(Li) detectors of different sizes. The following gamma rays (energies in keV and intensities within brackets) were definitely identified with the 169Yb decay: 20.7 (0.66 ± 0.04), 63.1 (124 ± 5), 93.6 (7.2 ± 0.3), 109.8 (50 ± 2), 117.3 (0.08 ± 0.04), 118.2 (5.4 ± 0.2), 130.5 (34 ± 2), 156.7 (0.023 ± 0.004), 177.2(59 ± 3), 198.0 (100), 240.4 (0.33 ± 0.02), 261.0 (4.7 ± 0.2), and 307.7 (28 ± 1). The recently reported weak gamma-ray peaks at 515 (0.008 ± 0.002) and 625 (0.010 ± 0.002) were also observed and could not be ruled out as not belonging to 169Yb. The recently reported gamma-ray peaks at 140, 160, 207, 288, 295, 316, 320, 328, 355, 371, 379, 396, and 417 were detected and shown not to be from the decay of 169Yb while those at 218, 229, 285, 304, 335, 388, 411, and 425 were not observed and upper limits were placed on their intensities. The presence of very weak peaks at 515 and 625 establishes the formation of the 633 keV state of 169Tm following electron capture decay of 169Yb as reported by George. (This level has been previously observed only in Coulomb excitation of 169Tm.) The total internal conversion coefficient for the 20.7 keV transition was determined for the first time from the direct measurement of the gamma-ray intensity as 51 ± 10 corresponding to an M1 transition.

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