High Spectral Response Research Articles

Photocatalytic degradation of norfloxacin antibiotic by a novel Cu-ZnO/BiOI/Bi2WO6 double Z-type heterojunction: Performance, mechanism insight and toxicity assessment

A novel double Z-type Cu-ZnO/BiOI/Bi2WO6 photocatalyst was synthesized using one-pot hydrothermal method. The effects of Bi2WO6 and Cu-ZnO contents, antibiotic concentration, catalyst dosage, solution pH value, coexisting ions, antibiotic types, mixed antibiotic types, water source and light source on the catalytic performance of the Cu-ZnO/BiOI/Bi2WO6 were investigated. Remarkably, under visible light irradiation, the removal rate of 20 mg/L norfloxacin reached 94.32 % within 120 min using the optimized Cu-ZnO/BiOI/Bi2WO6 photocatalyst, and its pseudo-first-order reaction rate constants were 5.63 and 1.80 times higher than those of BiOI and BiOI/Bi2WO6, respectively. The toxicity prediction and experimental findings indicated that the toxicity of the degraded norfloxacin (NOR) solution was notably diminished. The Cu-ZnO/BiOI/Bi2WO6 catalyst exhibited excellent salt tolerance, high reusability stability, universality and spectral response. Outstanding photocatalytic performance of Cu-ZnO/BiOI/Bi2WO6 photocatalyst is primarily due to the co-recombination of Cu-ZnO and Bi2WO6 on BiOI, which increases the surface area and active sites of the catalyst. More importantly, the double Z-type heterojunction, created through the intimate union of the semiconductor boundary within the composite catalyst, enhances the interface charge transport efficacy and the efficiency of separating photogenerated carriers. Finally, in conjunction with a diverse range of experimental methodologies, the degradation pathway of NOR through the Cu-ZnO/BiOI/Bi2WO6 composite catalyst and the electron transfer mechanism within the double Z-type heterojunction have been comprehensively elucidated. This study provides a pioneering reference for optimizing BiOI-based heterojunction catalysts and addressing antibiotic-contaminated wastewater treatment.

Quantification of UV Light-Induced Spectral Response Degradation of CMOS-Based Photodetectors.

High-energy radiation is known to potentially impact the optical performance of silicon-based sensors adversely. Nevertheless, a proper characterization and quantification of possible spectral response degradation effects due to UV stress is technically challenging. On one hand, typical illumination methods via UV lamps provide a poorly defined energy spectrum. On the other hand, a standardized measurement methodology is also missing. This work provides an approach where well-defined energy spectrum UV stress conditions are guaranteed via a customized optical set up, including a laser driven light source, a monochromator, and a non-solarizing optical fiber. The test methodology proposed here allows performing a controlled UV stress between 200 nm and 400 nm with well-defined energy conditions and offers a quantitative overview of the impact on the optical performance in CMOS-based photodiodes, along a wavelength range from 200 to 1100 nm and 1 nm step. This is of great importance for the characterization and development of new sensors with a high and stable UV spectral response, as well as for implementation of practical applications such as UV light sensing and UV-based sterilization.

High spectral responsivity and specific detectivity of p-MoS2/n-Si heterojunction photodetector for near-IR detection via facile solution process

High spectral responsivity and specific detectivity of p-MoS2/n-Si heterojunction photodetector for near-IR detection via facile solution process

A dual P‐layer 4H‐SiC p‐i‐n photodetector for the detection from extreme ultraviolet to ultraviolet‐A

AbstractA dual P‐layer 4H‐SiC p‐i‐n ultraviolet photodetector is proposed and studied. The modeling results of the photoelectric characteristics demonstrate the dual P‐layer structure could effectively reduce the recombination of the photogenerated carriers and separate more electron‐hole pairs near the surface of the device. And, the photodetector exhibits a significantly high response and detectivity, especially in the wavelength range of extreme ultraviolet to ultraviolet‐C. A high spectral response peak of 0.2 A/W corresponding to a quantum efficiency of 95.3% is achieved. Furthermore, an avalanche breakdown voltage as low as 182 V is observed. The dual P‐layer structure significantly presents an innovative approach for the advancement of future ultraviolet photodetectors applied in the detection at illumination wavelengths ranging from extreme ultraviolet to ultraviolet‐A.

Photomultiplication Enabling High‐Performance Narrowband Near‐Infrared Organic Photodetectors

AbstractContinuous monitoring of food quality, blood oxygen, or industrial processes require high‐throughput near‐infrared photodetectors. Due to excellent properties like low‐cost fabrication, flexibility and narrowband response, organic photodetectors (OPDs) have a huge market potential for such applications. An organic donor–acceptor blend with a low‐energy and broad charge transfer (CT) feature is utilized, circumventing the difficulties of obtaining organic materials with significant absorption beyond 1000 nm. The increasing recombination of such low‐energy gap materials that is detrimental for the quantum efficiency is overcome by applying two photocurrent multiplication (PM) mechanisms to the donor–acceptor blend. Combined with an optical micro‐cavity, this OPD achieves a spectral response (SR) of 15 A W−1 at 1092 nm. With its spectrally narrow response of only 18 nm, this OPD technology can be used for highly resolved measurements. Contrary to OPDs working in the photovoltaic mode, this detector is optimized for operation under reverse bias. With its high spectral response, low‐cost readout circuitry like CMOS can be used for signal detection.

Selenium-sensitized TiO2 p-n heterojunction thin films with high resistance to oxidation and moisture for self-driven visible-light photodetection

Semiconductor-sensitized TiO2 thin films have been widely applied in optoelectronic devices. Here we prepared narrow bandgap (∼1.77 eV) selenium (Se)-sensitized TiO2 thin films by spin-coating of Se inks onto a TiO2 mesoporous layer, which forms a p-Se/n-TiO2 heterojunction interface and holds promise for self-driven visible-light detection and sensing. Under irradiation by simulated sunlight and monochromatic visible-light, the resultant films exhibit large on-off switch ratio, fast response speed, and high spectral responsivity and detectivity at zero bias. Meantime, the p-Se/n-TiO2 films show notable photoresponse stability and can maintain 92% and 64% of photocurrent of the pristine device after 2-month air storage and 72 h water soaking, respectively. Such good oxygen and moisture resistance of Se/TiO2 thin films would be promising as applied in environmentally-stable heterojunction optoelectronic devices.

Manufacturing Br:CO3O4 /Si Heterojunction For Photodetector Applications

This research including, CO3O4 was prepared by the chemical spry pyrolysis, deposited film acceptable to assess film properties and applications as photodetector devise, studying the optical and optoelectronics properties of Cobalt Oxide and effect of different doping ratios with Br (2, 5, 8)%. the optical energy gap for direct transition were evaluated and it decreases as the percentage Br increase, Hall measurements showed that all the films are p-type, the current–voltage characteristic of Br:CO3O4 /Si Heterojunction show change forward current at dark varies with applied voltage, high spectral response, specific detectivity and quantum efficiency of CO3O4 /Si detector with 8% of Br ,was deliberate, extreme value with 673nm.

High Performance Polarization-Resolved Photodetectors Based on Intrinsically Stretchable Organic Semiconductors.

Polarization-sensitive photodetectors based on anisotropic semiconductors sense both the intensity and polarization state information without extra optical components. Here, a self-powered organic photodetector (OPD) composed of intrinsically stretchable polymer donor PNTB6-Cl and non-fullerene acceptor Y6 is reported. The PNTB6-Cl:Y6 photoactive film accommodates a remarkable 100% strain without fracture, exhibiting a high optical anisotropy of 1.8 after strain alignment. The resulting OPD not only shows an impressive faint-light detection capability (high spectral responsivity of 0.45 A W-1 and high specific detectivity of 1012 Jones), but also has a high anisotropic responsivity ratio of 1.42 under the illumination of parallel and traversed polarized light. To the best of the authors' knowledge, both the detector performance and polarization features are among the best-performing OPDs and polarization-sensitive photodetectors. As a proof-of-concept, polarization-sensitive OPDs are also utilized to set up a polarimetric imaging system and full-Stokes polarimeter. This work explores the potential of highly stretchable organic semiconductors for state-of-art polarization imaging and spectroscopy applications.

High and flat spectral responsivity of quartz tuning fork used as infrared photodetector in tunable diode laser spectroscopy

Infrared laser technology over the last decades has led to an increasing demand for optical detectors with high sensitivity and a wide operative spectral range suitable for spectroscopic applications. In this work, we report on the performance of a custom quartz tuning fork used as a sensitive and broadband infrared photodetector for absorption spectroscopy. The photodetection process is based on light impacting on the tuning fork and creating a local temperature increase that generates a strain field. This light-induced, thermoelastic conversion produces an electrical signal proportional to the absorbed light intensity due to quartz piezoelectricity. A finite-element-method analysis was used to relate the energy release with the induced thermal distribution. To efficiently exploit the photo-induced thermoelastic effects in the low-absorbance spectral region of quartz also, chromium/gold layers, acting as opaque surface, have been deposited on the quartz surface. To demonstrate the flat response as photodetectors, a custom tuning fork, having a fundamental resonance frequency of 9.78 kHz and quality factor of 11 500 at atmospheric pressure, was employed as photodetector in a tunable diode laser absorption spectroscopy setup and tested with five different lasers with emission wavelength in the 1.65–10.34 μm range. A spectrally flat responsivity of ∼2.2 kV/W was demonstrated, corresponding to a noise-equivalent power of 1.5 nW/√Hz, without employing any thermoelectrical cooling systems. Finally, a heterodyne detection scheme was implemented in the tunable diode laser absorption spectroscopy setup to retrieve the resonance properties of the quartz tuning fork together with the gas concentration in a single, fast measurement.

Differentiation of ultraviolet/visible photons from near infrared photons by MoS2/GaN/Si-based photodetector

Conventional photodetectors (PDs) generally exhibit a unipolar photoresponse within their responsive spectral range. Different from the traditional PDs, we report here a broadband PD based on the MoS2/GaN/Si heterojunction that shows a unique phenomenon of wavelength selectivity through photocurrent polarity inversion. Overall, the device can differentiate the photons of the ultraviolet (UV)/visible region from that of the near infrared (NIR) region. This polarity inversion is explained with the help of the band diagram and the wavelength dependent photothermoelectric (PTE) effect in MoS2. The vertical transport characteristics of the MoS2/GaN/Si device exhibit a high spectral response in a broad range of wavelengths (300–1100 nm) in a self-biased mode. The maximum response of the device is found to be 23.81 A/W at a wavelength of 995 nm. Our results demonstrate a route for the development of PDs without filter that possess a lot of potential for the futuristic photonic devices.

Self-Powered Low-Cost UVC Sensor Based on Organic-Inorganic Heterojunction for Partial Discharge Detection.

Power outages caused by the aging of high-voltage power facilities can cause significant economic and social damage. To prevent such problems, it is necessary to implement a widespread and sustainable monitoring system. Partial discharge (PD) is a preliminary symptom of power equipment aging accompanying the light, typically in the UV range. UVC (200-280nm) is more useful than UVA and UVB because of low interference from the environment owing to its solar-blindness by the stratosphere. Therefore, to realize a wide-range and durable diagnosis system, it is necessary to develop sensors that can selectively detect UVC, while enabling mass production at low-cost and low power consumption. Here, a solution-processable photodiode sensor that is inexpensive, mass-producible, and self-powered with selective UVC detection is developed. The optoelectronic characteristics of photodiode consisting of organic p-polymer and inorganic n-ZnO nanoparticles are systematically studied to determine the optimum p-type polymer and its thickness. The device shows high-performance: fast response time (rise/fall time: 36.6/37.0ms) and high spectral response in the UVC region (maximum responsivity of 20mA W-1 ) under self-powered operation. Furthermore, the practical application of the device to detect PD signals with a visual alarm system under UVC release conditions is demonstrated.

Potential of machine learning and WorldView-2 images for recognizing endangered and invasive species in the Atlantic Rainforest

We found high accuracy classification (Fmeasure = 95%, on cross-validation) of Araucaria angustifolia (Bertol.) Kuntze, an endangered native species, and Hovenia dulcis Thunb. an aggressive, invasive alien species in WorldView-2 multispectral images. In applying machine learning algorithms, the spectral attributes mainly related to the near-infrared band were the most important for the models. It is difficult to classify tree species in tropical rainforests due to the high spectral response’s diversity of existing species, as well as to adjust efficient machine learning techniques and orbital image resolution. To explore the spectral and textural response of an endangered species (A. angustifolia) and an invasive species (H. dulcis) in WorldView-2 multispectral images, testing its recognition capability by machine learning techniques. We used a WordView-2 (2016) image with 0.5-m spatial resolution. Then we manually clipped the canopy area of the two species in this image using two compositions: True color composition (R=660 nm, G=545 nm, B=480 nm) and near-infrared composition (NIR-2=950 nm, G=545 nm, B=480 nm). Thus, we applied spectral and textural descriptors (pyramid histogram of oriented gradients—PHOG and Edge Filter), which selects the most representative features of the dataset. Finally, we used artificial neural networks (ANN) and random forest (RF) for tree species classification. The species classification was performed with high accuracy (Fmeasure = 95%, on cross-validation), essentially for spectral attributes using the near-infrared composition. RF surpassed the ANN classification rates and also proved to be more stable and faster for training and testing. The WorldView-2 multispectral sensor showed the potential to provide sufficient information for classifying two species, proving its usefulness in this phytophysiognomy where hyperspectral sensors are generally used for this type of classification.

AlGaN/AlN/SiC Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors with Al2O3 Gate-Oxide and Step-Graded AlGaN Channel

Al0.75Ga0.25N/n-AlxGa1-xN/Al0.75Ga0.25N/AlN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs), grown on a SiC substrate, with step-graded Si-doped (n = 3 × 1018 cm-3) widegap AlxGa1-xN channel and Al2O3 gate-dielectric are investigated. Increased Al-compositions with x = 0.25, 0.5, and 0.75 towards the buffer were devised in the composite widegap channel. The high-k Al2O3 dielectric/passivation layer was grown by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. Experimental comparisons were made with respect to a conventional Schottky-gate HFET.The epitaxial structure of the studied Al2O3-dielectric Al0.75Ga0.25N/n-AlxGa1-xN/Al0.75Ga0.25N/AlN MOS-HFET (sample A) and Schottky-gate HFET (sample B). Both devices have the identical epitaxial structure grown on a SiC substrate by using a low-pressure metal-organic chemical vapor deposition (LP-MOCVD) system. The layer structure includes an undoped AlN buffer, a 20-nm undoped Al0.75Ga0.25N barrier, a 150-nm step-graded Si-doped (n = 3 × 1018 cm-3) AlxGa1-xN channel (x = 0.25, 0.5, and 0.75), and a 20-nm undoped Al0.75Ga0.25N barrier. Standard photolithography and lift-off techniques were used for device processing. For sample B, mesa etching was performed with respect to a 100-nm thick Ni barrier by using an inductively coupled-plasma reactive ion etcher (ICP-RIE). Flow rates were tuned and set at 10 sccm and 20 sccm for the mixed etching gases of BCl3 and Cl2, respectively. The 20-nm undoped Al0.75Ga0.25N barrier was etched away before deposition of source/drain electrodes. Ti (10 nm)/Al (50 nm)/Ni (10 nm)/Au (50 nm) were evaporated. The source/drain ohmic contacts were formed by annealing the sample for 25 seconds at 900°C by using a rapid thermal annealing (RTA) system (ULVAC MILA-5000). Then, 30-nm thick Al2O3 layer was deposited on the Al0.75Ga0.25N barrier by using the USPD technique. Finally, gate electrode of Ni (100 nm)/Au (50 nm) was evaporated after gate photolithography. As for sample A, the gate electrode was formed directly on the surface of Al0.75Ga0.25N barrier without oxide deposition.Improved device performance of the present MOS-HFET design have been obtained, including maximum drain-source current density (IDS, max ) of 130.1 A/mm at VGS = 10 V and VDS = 20 V, IDS at VGS = 0 V (IDSS0 ) of 83.1 mA/mm, on/off-current ratio (Ion /Ioff ) of 1.4 × 107, maximum extrinsic transconductance (gm, max ) of 11.8 mS/mm, two-terminal off-state gate-drain breakdown voltage (BVGD ) of -404 V, and three-terminal on-state drain-source breakdown voltage (BVDS ) of 364 V at 300 K. The present MOS-HFET design has also shown high spectral responsivity (SR) of 737 A/W under 250-nm deep-UV radiation at 300 K.

Simulation of AlGaN MSM detector for investigating the effect varying absorber layer thickness

For detecting feeble Ultra-Violet (UV) signals it is essential that front-illuminated photodetector (PD) should havethick photo-absorbing layer with thin transparent metal electrodes and antireflective coating (ARC) so as to getmore photocurrent and low dark current.Since detector geometry influences its performance, so it is very important to optimize layer thickness parameters. In proposed work fixed area Al0.5Ga0.5N/AlN/ Sapphire based Metal-Semiconductor-Metal (MSM)PDbased has been analyzed for optimum value of active layer thickness and inter-electrode thickness.In addition to take benefit of large Schottky barrierGold material has beenutilized for electrodes. It has been illustrated in past research studies that with the increase in thickness of AlGaN layer, more incident energy can be absorbed for large EHPs generation which lead to increased responsivity.However, few research papers have related the effect of variations inthickness of active layerwith electron velocity which has significant effect on dark current density, recombination rateand additionally on efficiency.So for further development and widespread implementation of AlGaN/GaN based detectors there is need to study the effect of variation in photo-absorber layer thickness on closely related performance parameters so as to select its optimum value.Current Voltage (IV)-characteristics,recombination rate, current density plots and spectral response have been investigated using Atlas-Silvaco simulation tool.In addition for electrode thickness variation,transmission and absorptionplots are alsoinvestigated. For the proposed MSM structure, it has been observed that dark current density tends to increase
 
 beyond the optimum value of thickness of AlGaN layerwith specific absorption coefficient. Good transmission of light with high spectral response can be obtained with optimum value of electrode thickness.These observations can be suitable for improving the detectivity in support of various UV detection applications requiring good sensitivity and high signal to noise ratio.

Optical modeling of high-performance GaAs based photodetector with periodic right triangular texturization on nanopillar arrays structure

The high spectral responsivity of a photodetector depends upon proficient light absorption. In this respect, surface reflectance possesses a serious threat to the effective light absorption mechanism resulting in poor quantum efficiency. This paper presents an analytical investigation of a GaAs based periodic right triangular cut textured vertical nanopillar structural model deployed over a 50 μm × 50 μm planar front detector’s surface in reducing surface reflectivity. The geometrical analysis of the proposed model exhibits a 99.9% absorbance and 0.85 A W−1 photoresponsivity at 0.8 μm operating wavelength with a mere 0.5 μm depletion width.

Influence of laser energy on the optoelectronic properties of NiO/Si heterojunction

In the current work, NiONPs/Si Heterojunction Photodetector was fabricated using a drop-casting method of the Nickel Oxide (NiO) nanomaterial (produced by laser ablation in the water) on silicon (Si) substrate. The impact of laser energy on the preparation of NiO nanoparticles was investigated. The shape of the NiO NPs was a quasi-spherical particle with average particles size 16, 20, and 24 nm with high aggregations. The bandgap was direct and varying from 3.8 to 3.6 eV; relies on the laser energy. The current-voltage characteristics of NiO/Si heterostructure photodetector have a good rectifying property with suitable high spectral responsivity at the UV region, which found that the best value is 0.8 A/W @ 330 nm for a sample produced at 700mJ.

Preparation and characterization of ZnMgO nanostructured materials as a photodetector

In this work, ZnMgO/Si Heterojunction Photodetector was fabricated by deposited a Zinc doped Magnesium Oxide (ZnMgO) Nanostructure (prepared via laser ablation in the water) on silicon (Si) substrate using the drop-casting method. X-ray diffraction XRD and scanning electron microscopy SEM were used to obtain properties of the prepared nanostructure material. X-ray diffraction results showed that ZnMgO Nanoparticles have a hexagonal structure at 2Θ = 34:31° and 34.76°. The scanning electron microscopy image displays a flower-like hierarchical structure with a full array of about 2µm. The current-voltage (I-V) characteristics of ZnMgO/Si Heterostructure Photodetector possess a good rectifying property with suitable an ideality factor which changes from 2.63 to 1.241 as Mg doping increases and in addition to the high spectral responsivity with the low dark current

Luminescent properties and energy transfer of novel NIR K(Ga/Al)11O17:Cr3+,Yb3+ phosphors for solar cells

Novel Cr3+–Yb3+ codoped KGa11O17 and KAl11O17 phosphors (referred to as KGO:Cr3+,Yb3+ and KAO:Cr3+,Yb3+) were prepared via a traditional solid-state method. X-ray diffraction, scanning electron microscope equipped with an energy-dispersive spectrometer, and photoluminescence spectra were used to characterize the phase purity, chemical composition, and luminescence properties of the phosphors. The obtained KGO:Cr3+ and KAO:Cr3+ phosphors have high efficiency and broad absorption in the ultraviolet and visible (UV–vis) region. Under 300/420 nm excitation, KGO:Cr3+ and KAO:Cr3+ phosphors show deep red emission at about 712 nm. When Cr3+–Yb3+ are codoped into the KGO:Cr3+/KAO:Cr3+ matrix, the effective energy transfer from the Cr3+ to Yb3+ ions occurs, thus achieving intense near-infrared (NIR) emission. As a consequence, the high-energy UV–vis light can be efficiently converted into low-energy NIR light in KGO:Cr3+,Yb3+/KAO:Cr3+,Yb3+ phosphors based on the energy transfer process of the Cr3+→Yb3+ ions, which matches well with the high spectral response region of crystalline silicon (c-Si) solar cells. The experimental results reveal that KGO:Cr3+,Yb3+and KAO:Cr3+,Yb3+ phosphors are promising solar spectral conversion materials for c-Si solar cells.

Carrier transport and photoconductive gain mechanisms of AlGaN MSM photodetectors with high Al Content

We have fabricated the AlGaN solar-blind ultraviolet metal–semiconductor–metal (MSM) photodetectors (PDs) with an Al composition of 0.55. The surface roughness and dislocations of the high-Al-content Al0.55Ga0.45N epitaxial layer are analyzed by atomic force microscopy and transmission electron microscopy, respectively. The device exhibits high spectral responsivity and external quantum efficiency due to the photoconductive gain effect. The current reveals a strong dependence on high temperatures in the range of 4–10 V. Moreover, the Poole–Frenkel emission model and changing space charge regions are employed to explain the carrier transport and photoconductive gain mechanisms for the AlGaN PD, respectively.

High-efficiency narrow-band plasmonic hot electron conversion from nanoscale sodium–silicon heterostructures

Plasmonic harvesting of hot electrons has stimulated intensive research activities for applications ranging from sub-bandgap photodetection to photocatalysis. Both high photoelectric conversion efficiency and tunable spectral response are pursued by manipulating resonant metal–semiconductor (M–S) nanostructures. Although noble plasmonic metals have been exclusively employed in hot electron conversion studies, exploring new materials may offer an additional degree of freedom to manipulate the hot electron generation, transport, and emission processes. In this paper, we propose to employ the low-loss alkali metal sodium as an alternate plasmonic material for developing a narrow-band resonant hot electron device. Based on a backside-illumination (BSI) configuration where plasmonic hot electrons generate locally at the M–S interface, the transport loss can be significantly suppressed. Thanks to its ultralow imaginary part of the permittivity, bringing Na into the BSI design allows for efficient shrinking of the resonant linewidth down to sub-20 nm. Another intriguing feature is that Na has more preferred electron density of state distribution for facilitating hot electron emission at the M–S junction. The optimized Na BSI device can yield a photocurrent responsivity up to 50 mA/W at a wavelength of 1400 nm as predicted by our electromagnetic simulation and theoretical model. Our study highlights that the alkali metal could be a promising alternative material for the development of high-Q resonant hot electron devices for near-infrared wavelengths.