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Graphene quantum dots doped ZnO superstructure (ZnO superstructure/GQDs) for weak UV intensity photodetector application
摘要： Usually, the photoresponse performances of zinc oxide based ultraviolet (UV) photodetector can be enhanced by improving the nanostructure of zinc oxide. Here, we demonstrate a kind of weak ultraviolet intensity photodetector which bases on ZnO superstructure doped with graphene quantum dots (ZnO superstructure/GQDs). The ZnO superstructure includes a ZnO nanoflower on the top of ZnO nanorod. The nanoflower has large specific surface area that is favor to the absorption of weak UV light, and the nanorod provides a good route for carriers transport. Also, the GQDs can assist the absorption of UV and the transport of carriers. The photo-response performance of the ZnO superstructure/GQDs we measured is obtained at a working bias of 3 V and an irradiate condition of 50 μW/cm2, under the excitation wavelength 365 nm. The results show that ZnO superstructure/GQDs has a low dark current (40 nA) and a good photocurrent (2.1 μA) in a low irradiation and power supply condition, and we calculate the current ratio of on/off is about 52.5 times. Further, we discuss in-depth the synthesis mechanism of ZnO superstructure and the transport mechanism of photo-generated carriers in this paper. At the same time, we develop a UV signal acquisition and voltage conversion system, which proves the practical application reference of ZnO superstructure/GQDs for weak UV intensity photodetector.
关键词： Weak ultraviolet detector,Practical application,Graphene quantum dot doping,ZnO superstructure
更新于2025-09-23 15:19:57
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Determination of local muon flux using astronomical Charged Coupled Device
摘要： As an abundant component of secondary cosmic rays at the Earth, muons carry significant data, such as information on mass number of primary particles producing extensive air showers. Anyhow, the total muon flux is an important observable in many phenomena, for example it is suggested that the muon flux is influenced by the level of solar activity at the Earth, while the neutrino anomaly and hadronic interaction models are studied through the products of muon decay. As a result a part of any cosmic ray detector is designed to observe muons, count and evaluate their energy and angular distribution. Thus a simple method was started in Research Institute for Astronomy and Astrophysics of Maragha, University of Maragheh to study the recorded tracks of particles by an astronomical CCD at 1478 m above sea level. To analyze recorded data and determine the muon flux from experiments, the flux of secondary atmospheric muons simulated with CORSIKA code (version 6.9) to study the muon angular distribution for our geographical location (latitude: 46.2534 E, longitude: 37.3892 N). The data used here were gathered during a ground run on 4 months (of 2016 and 2017), at Maragheh, Iran. The paper presents numerical results of the muon's flux obtained at 1478 m above sea level which is in good agreement with expected values from simulations. The results were compared with experimental data from different experiments.
关键词： Simulation,CORSIKA,Cosmic rays,Detector,Muon,CCD
更新于2025-09-23 15:19:57
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The origin of distorted intensity pattern sensed by a lens and antenna coupled AlGaN/GaN-HEMT terahertz detectors
摘要： Here, we report artefacts in the intensity pattern of a focused terahertz beam around 1 THz by scanning photocurrents as a function of the beam location and the frequency. Although the exact distortion is found with our specific antenna design, we believe similar artefacts could be commonplace in antenna-coupled FET terahertz detectors when the beam spot becomes comparable with the antenna size. To eliminate such artefact, new antenna designs are welcomed to achieve strong asymmetry in the terahertz field distribution under the gate while maintaining a more symmetric radiation pattern for the whole antenna.
关键词： high electron mobility transistor,terahertz detector,self-mixing,local electrical field
更新于2025-09-23 15:19:57
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Photoelectric properties of SnO2: Ag/Pa??Si heterojunction photodetector
摘要： N-type Tin dioxide thin films with thickness (350 nm) prepared by thermal evaporation method. The thin film SnO2 was doped with Ag by the rate (0.01, 0.02 and 0.03). Atomic Force Microscopic (AFM) was adopted to determine the grain size and roughness of the film surface. The electrical properties were determined by mean of Hall Measurement system and mobility was calculated. SnO2: Ag/P–Si photodetectors demonstration the highest described visible responsivity of (0.287 A/W) with the Ag ratio of (0.03). I–V characteristics with different power density were measured. The best sensitive value of the spectral response, specific detectivity and quantum efficiency at wavelength (422 nm).
关键词： Ag/P–Si,Quantum efficiency,Detector,SnO2,Mobility
更新于2025-09-23 15:19:57
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Three-dimensional Lead Iodide Perovskitoid Hybrids with High X-ray Photoresponse
摘要： Large organic A cations cannot stabilize the 3D perovskite AMX3 structure because they cannot be accommodated in the cubo-octhedral cage (do not follow the Goldschmidt tolerance factor rule), and they generally template low-dimensional structures. Here we report that the large di-cation aminomethylpyridinium (AMPY), can template novel 3D structures which resemble conventional perovskites. They have the formula (xAMPY)M2I6 (x = 3 or 4, M = Sn2+ or Pb2+) which is doubled the AMX3 formula. However, because of the steric requirement of the Goldschmidt tolerance factor rule, it is impossible for (xAMPY)M2I6 to form proper perovskite structures. Instead, a combination of corner-sharing and edge-sharing connectivity is adopted in these compounds leading to the new 3D structures. DFT calculations reveal that the compounds are indirect-bandgap semiconductors with direct bandgaps presenting at slightly higher energies and dispersive electronic bands. The bandgaps of the Sn and Pb compounds are ~ 1.7 eV and 2.0 eV, respectively, which is slightly higher than the corresponding AMI3 3D perovskites. The Raman spectra for the compounds are diffuse, with a broad rising central peak at very low frequencies around 0 cm-1, a feature that is characteristic of dynamical lattices, highly anharmonic, and dissipative vibrations very similar to the 3D AMX3 perovskites. Devices of (3AMPY)Pb2I6 crystals exhibit clear photoresponse under ambient light without applied bias, reflecting a high carrier mobility (μ) and long carrier lifetime (τ). The devices also exhibit sizable X-ray generated photocurrent with a high μτ product of ~1.2×10-4 cm2 /V and an X-ray sensitivity of 207 μC·Gy-1·cm-2.
关键词： Metal halide hybrids,mixed cations,photoresponse,X-ray detector,anomalous bandgap behavior
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Shenzhen, China (2019.9.3-2019.9.6)] 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Ultra-sensitive Detection of Heavy Metal Using a Fiber Grating-Assisted Plasmonic Electrochemical Sensor
摘要： We demonstrate the performance enhancement of field-effect transistor (FET)-based plasmonic terahertz (THz) detector with monolithic integrated antenna in low-impedance regime and report the experimental results of Si MOSFET impedance in THz regime using 0.2-THz measurement system. By designing FET with low-impedance ranges (<1 kΩ) and integrating antennas with impedances of 50 and 100 Ω, we found that our low-impedance MOSFETs have the input impedance criterion of 50 Ω at 0.2 THz and the MOSFETs with thinner gate oxide show the highly enhanced plasmonic photoresponses at 50-Ω antenna by 325 times from the result of the detector without antenna.
关键词： terahertz,impedance,photoresponse,MOSFET,detector,plasmonic
更新于2025-09-23 15:19:57
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The laser power effect on the performance of gas leak detector based on laser photo-acoustic spectroscopy
摘要： The use of a homemade gas leak detector based on laser photo-acoustic spectroscopy for fast and sensitive trace gas detection is reported. To obtain optimal acoustic resonator dimensions, resonant frequency variations in terms of resonator's length and radius were simulated, and then a gas leak detector based on photo-acoustic theory was designed and fabricated. The system limit of detection to trace NO2, SO2 and SF6 was 92, 270 and 8 ppb respectively. Therefore, this system can be used as a sensitive gas sensor for detecting partial leakage of some environmental and industrial pollutants. Variations of the resonant frequency versus various concentrations of NO2, SO2 and SF6 in the presence different buffer gases were studied, and results showed that the lighter buffer gas gives a higher resonance frequency. Also, variations of the photo-acoustic signal and SNR of these gas samples in terms of various CO2 laser power at the presence different buffer gases were investigated, and the saturation laser power for each experiment was obtained. Finally, it was shown that experimental results are in good agreement with photo-acoustic theory.
关键词： Photo-acoustic signal,CO2 laser power,gas leak detector,resonant frequency,Infrared spectroscopy
更新于2025-09-23 15:19:57
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Laser-generated ns plasma pulses characterized using SiC Schottky diode
摘要： The nonequilibrium plasma generated by nanosecond laser pulse is characterized using a SiC detector connected in time-of-flight configuration to measure the radiations emitted from the plasma. Different metallic targets were irradiated by the pulsed laser at an intensity of 1010 W/cm2 and 200 mJ pulse energy. The SiC allows detecting ultraviolet radiations and soft X-rays, electrons, and ions. The obtained plasma has a temperature of the order of tens to hundreds eV depending on the atomic number of the irradiated target and ion accelerations of the order of 100 eV per charge state.
关键词： SiC-TOF,SiC detector,Laser-generated plasma,Photopeak
更新于2025-09-23 15:19:57
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[IEEE ESSCIRC 2019 - IEEE 45th European Solid State Circuits Conference (ESSCIRC) - Cracow, Poland (2019.9.23-2019.9.26)] ESSCIRC 2019 - IEEE 45th European Solid State Circuits Conference (ESSCIRC) - A Hybrid THz Imaging System With a 100-Pixel CMOS Imager and a 3.25a??3.50 THz Quantum Cascade Laser Frequency Comb
摘要： The terahertz frequency range beyond 3 THz has exciting potential to have a transformative impact in a wide range of applications, including chemical and biomedical sensing, spectroscopy, imaging, and short-distance wireless communication. While there have been significant advancements in silicon-based THz imagers in the frequency ranges below 1 THz, technological development beyond 3 THz has been impeded by the lack of solid-state sources in this frequency range. In addition, the design space beyond 3 THz opens up fundamentally new challenges across electronics and the electromagnetic interface. In this spectral range, the wavelength is small enough (λox ≈ 50 μm at 3 THz) that a vertical via from the top antenna layer to the detector is a distributed element (transmission line or radiator). In this letter, we follow a careful circuits-electromagnetics co-design approach toward a hybrid imaging system with a 100-pixel CMOS imager that interfaces with a THz quantum cascade laser frequency comb that spans 3.25–3.5 THz with mode spacing of 17 GHz. The array chip, while designed for an optimal operation across 2.7–2.9 THz, demonstrates an average noise equivalent power (NEP) (across pixels) of 1260 pW/√Hz between 3.25–3.5 THz and a projected NEP of 284 pW/√Hz across the design range of 2.7–2.9 THz. To the best of our knowledge, we demonstrate for the first time full THz imaging in a hybrid quantum cascade laser (QCL)–CMOS fashion. This approach allows future works to leverage both QCL and CMOS technologies to demonstrate new technological advances for systems in the 1–10 THz range.
关键词： quantum cascade laser,THz imaging,terahertz,detector,imaging,CMOS,silicon,hybrid imaging
更新于2025-09-23 15:19:57
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CMOS-coupled NaI scintillation detector for gamma decay measurements
摘要： We report an all-solid-state gamma-ray scintillation detector comprised of a NaI(Tl) crystal and a scientific-grade CMOS camera. After calibration, this detector exhibits excellent linearity over more than three decades of activity levels ranging from 10 mCi to 400 nCi. Because the detector is not counting pulses, dead-time correction is not required. Compared to systems that use a photomultiplier tube, this detector has similar sensitivity and noise characteristics on short time scales. On longer time scales, we measure drifts of a few percent over several days, which can be accommodated through regular calibration. Using this detector, we observe that when high activity sources are brought into close proximity to the NaI crystal, several minutes are required for the measured signal to achieve a steady state.
关键词： gamma-ray scintillation detector,dead-time correction,photomultiplier tube,NaI(Tl) crystal,CMOS camera
更新于2025-09-23 15:19:57