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An Improved Room-Temperature Silicon Terahertz Photodetector on Sapphire Substrates
摘要： We design and fabricate a good performance silicon photoconductive terahertz detector on sapphire substrates at room temperature. The best voltage responsivity of the detector is 6679 V/W at frequency 300 GHz as well as low voltage noise of 3.8 nV/Hz1/2 for noise equivalent power 0.57 pW/Hz1/2. The measured response time of the device is about 9 ??s, demonstrating that the detector has a speed of >110 kHz. The achieved good performance, together with large detector size (acceptance area is 3 ??m×160 ??m), simple structure, easy manufacturing method, compatibility with mature silicon technology, and suitability for large-scale fabrication of imaging arrays provide a promising approach to the development of sensitive terahertz room-temperature detectors.
关键词： terahertz,room-temperature,sapphire substrates,silicon,photodetector
更新于2025-09-23 15:19:57
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Oxygen Vacancies Enabled Porous SnO <sub/>2</sub> Thin Films for Highly Sensitive Detection of Triethylamine at Room Temperature
摘要： Detection of volatile organic compounds (VOCs) at room temperature (RT) currently remains a challenge for metal oxide semiconductor (MOS) gas sensors. Herein, we for the first time report on the utilization of porous SnO2 thin films for RT detection of VOCs by defect engineering of oxygen vacancies. The oxygen vacancies in the three-dimensional ordered SnO2 thin films, prepared by a colloidal template method, can be readily manipulated by thermal annealing at different temperatures. It is found that oxygen vacancies play an important role in the RT sensing performances, which successfully enables the sensor to respond to triethylamine (TEA) with an ultrahigh response, e.g. 150.5 to 10 ppm TEA in a highly selective manner. In addition, the sensor based on oxygen vacancy-rich SnO2 thin films delivers a fast response and recovery speed (53 and 120 s), which can be further shortened to 10 and 36 s by elevating the working temperature to 120 oC. Notably, a low detection limit of 110 ppb has been obtained under RT. The overall performances surpass most previous reports on TEA detection at RT. The outstanding sensing properties can be attributed to the porous structure with abundant oxygen vacancies, which can improve the adsorption of molecules. The oxygen vacancy engineering strategy and the on-chip fabrication of porous MOS thin film sensing layers deliver a great potential for create high-performance RT sensors.
关键词： Oxygen vacancy,Porous film,Gas sensor,Tin dioxide,Room temperature
更新于2025-09-23 15:19:57
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Controlled synthesis of ultrathin MoS <sub/>2</sub> nanoflowers for highly enhanced NO <sub/>2</sub> sensing at room temperature
摘要： Fabrication of a high-performance room-temperature (RT) gas sensor is important for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices. Herein, we developed a NO2 gas sensor based on ultrathin MoS2 nanoflowers with high sensitivity at RT. The MoS2 flower-like nanostructures were synthesised via a simple hydrothermal method with different growth times of 24, 36, 48, and 60 h. The synthesised MoS2 nanoflowers were subsequently characterised by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy. The petal-like nanosheets in pure MoS2 agglomerated to form a flower-like structure with Raman vibrational modes at 378 and 403 cm?1 and crystallisation in the hexagonal phase. The specific surface areas of the MoS2 grown at different times were measured by using the Brunauer–Emmett–Teller method. The largest specific surface area of 56.57 m2 g?1 was obtained for the MoS2 nanoflowers grown for 48 h. This sample also possessed the smallest activation energy of 0.08 eV. The gas-sensing characteristics of sensors based on the synthesised MoS2 nanostructures were investigated using oxidising and reducing gases, such as NO2, SO2, H2, CH4, CO and NH3, at different concentrations and at working temperatures ranging from RT to 150 °C. The sensor based on the MoS2 nanoflowers grown for 48 h showed a high gas response of 67.4% and high selectivity to 10 ppm NO2 at RT. This finding can be ascribed to the synergistic effects of largest specific surface area, smallest crystallite size and lowest activation energy of the MoS2-48 h sample among the samples. The sensors also exhibited a relative humidity-independent sensing characteristic at RT and a low detection limit of 84 ppb, thereby allowing their practical application to portable IoT-based devices.
关键词： gas sensing,room temperature,hydrothermal synthesis,MoS2 nanoflowers,NO2 gas sensor
更新于2025-09-23 15:19:57
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Low-threshold stimulated emission in perovskite quantum dots: single-exciton optical gain induced by surface plasmon polaritons at room temperature
摘要： Colloidal perovskite quantum dots are candidate materials for solution-processable lasers, although stimulated emission in a semiconductor usually occurs in the multiexciton regime. Due to the quantum-confinement effect of semiconductor quantum dots, the non-radiative recombination transition dominates the relaxation of multiexcitons. Hence, the implementation of low-threshold stimulated emission of perovskite quantum dots in the single-exciton regime is meaningful. Herein, we show that this problem can be partially solved by employing a locally enhanced electric field. By applying the metal surface plasmon resonance energy-transfer effect, we demonstrate a considerable reduction of the optical gain threshold due to the newly generated coupling level induced by the local surface plasmon, and obtain optical gain in the single-exciton regime at room temperature in colloidal perovskite quantum dots. At the same time, we achieve a more than fourfold reduction in the amplified spontaneous emission threshold. This may provide a new concept for the further design of low-threshold stimulated emission colloidal nanocrystal lasers and even for improving their energy conversion efficiency.
关键词： surface plasmon polaritons,stimulated emission,optical gain,room temperature,perovskite quantum dots
更新于2025-09-23 15:19:57
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Design and optimization of perovskite plasmonic nano-laser for operation at room temperature
摘要： This work presents the design and optimization of a cascade nano-laser using CH3NH3PbI3 perovskite. Due to increasing threshold gain with decreasing device size and high Auger losses, the use of perovskite as the active medium in the cascade nano-laser was proposed, as the material possesses a high emission rate in the visible wavelength region, with relative ease of device fabrication. By optimizing the thickness of the perovskite, its width, and the thickness of the silica used, photonic and plasmonic modes were created, which were further considered to permit the generation of lasing, using their respective Purcell factors. The pump wavelength considered was 400 nm, with the laser emission then at 537 nm. For suitability of plasmonic lasing, a Purcell factor FP of 1.22 is reported here, with no possibility for photonic lasing due to its FP value being less than 1 in this design. However, mode-crossing effects were observed in the plasmonic mode at λ = 400 nm for two designs: at a silica thickness of 27.5 nm with perovskite thickness and width of 100 and 300 nm, respectively, and at a silica thickness of 30 nm with perovskite thickness and width of 95 and 300 nm, respectively. These mode-crossing effects can be further analyzed to use these devices in the design of potential new sensor systems, mainly for gas and chemical sensing, exploiting the refractive index sensing capability as a means to determine the concentration of the gases, or other chemicals, under study.
关键词： room temperature,plasmonic nano-laser,Purcell factor,perovskite,mode-crossing effects
更新于2025-09-23 15:19:57
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MoS2 Nanosheets Sensitized with Quantum Dots for Room-Temperature Gas Sensors
摘要： The Internet of things for environment monitoring requires high performance with low power-consumption gas sensors which could be easily integrated into large-scale sensor network. While semiconductor gas sensors have many advantages such as excellent sensitivity and low cost, their application is limited by their high operating temperature. Two-dimensional (2D) layered materials, typically molybdenum disulfide (MoS2) nanosheets, are emerging as promising gas-sensing materials candidates owing to their abundant edge sites and high in-plane carrier mobility. This work aims to overcome the sluggish and weak response as well as incomplete recovery of MoS2 gas sensors at room temperature by sensitizing MoS2 nanosheets with PbS quantum dots (QDs). The huge amount of surface dangling bonds of QDs enables them to be ideal receptors for gas molecules. The sensitized MoS2 gas sensor exhibited fast and recoverable response when operated at room temperature, and the limit of NO2 detection was estimated to be 94 ppb. The strategy of sensitizing 2D nanosheets with sensitive QD receptors may enhance receptor and transducer functions as well as the utility factor that determine the sensor performance, offering a powerful new degree of freedom to the surface and interface engineering of semiconductor gas sensors.
关键词： Nitrogen dioxide,Room temperature,Gas sensor,Molybdenum disulfide,Quantum dot
更新于2025-09-23 15:19:57
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Enhanced transmittance and mobility of p-type copper iodide thin films prepared at room temperature via a layer-by-layer approach
摘要： High-quality, transparent, conducting, p-type γ-CuI thin films are prepared via an innovative layer-by-layer procedure based on the traditional simple iodination of Cu films (referred to as the LBL-I method) at room temperature (RT). The structure, morphology, and optoelectronic properties of the γ-CuI are investigated as functions of the per layer thickness. The final thicknesses of LBL-I γ-CuI films are consistent with that in the film prepared by the traditional one-step method (TOS). X-ray diffraction analysis reveals that all the films are polycrystalline with the most dominant (111) direction of the zinc blende structure, indicating the facile and successful fabrication of γ-CuI. Compared with the TOS film, the LBL-I films display enhanced transmittance and mobility. The higher transmittance of >80% in the visible region of LBL-I films was attained due to the smaller root-mean-square roughness values of 23?28 nm. The 50 nm/l LBL-I CuI films have mobility values of 6.9?9.4 cm2 V-1 s-1, and lower resistivity of 0.039-0.05 Ω cm, which assist studies on applications of γ-CuI thin films in transparent electronics.
关键词： p-type transparent conductor,room-temperature synthesis,layer by layer procedure
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE SENSORS - New Delhi, India (2018.10.28-2018.10.31)] 2018 IEEE SENSORS - Hierarchical MnO<inf>2</inf> Nanoflowers Based Efficient Room Temperature Alcohol Sensor
摘要： In the present work, hierarchical 3-D MnO2 nanoflowers (consisting of 2D nanosheets) were synthesized employing hydrothermal technique and subsequently alcohol sensing performance of the MnO2 NFs was investigated. The morphological (FESEM, Transmission Electron Microscopy), and surface compositional (X-ray Photoelectron Spectroscopy) characterizations were carried out. Lattice fringe of TEM image confirmed that constituents of 3-D nanoflower to be birnessite (i.e. δ-MnO2) 2-D nanosheets. In addition, core level XPS spectra validated the presence of mixed valence state of Mn (i.e. Mn3+ and Mn4+states) in the MnO2 NFs. Further, Electrochemical Impedance Spectroscopy measurement (Mott Schottky analysis) revealed that the n-type conductivity of MnO2 NFs based sensing layer. It is clearly observed from the transient response characteristics that the device offered promising room temperature sensing performance towards alcohols (i.e. methanol, ethanol and 2-propanol). However, the device offered better sensing performance towards methanol than that of ethanol and 2-propanol. The response time and recovery time of the sensor also found to be moderately fast at room temperature. Interestingly, the device resistance was increased in presence of reducing vapor (although MnO2 NFs is a n-type material).
关键词： Birnessite (i.e. δ-MnO2),Room temperature Alcohol sensor,Anomalous gas sensing performance,Hierarchical 3-D MnO2 nanoflowers
更新于2025-09-19 17:15:36
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An Efficient Room Temperature Ethanol Sensor Device Based on p-n Homojunction of TiO <sub/>2</sub> Nanostructures
摘要： In this paper, an efficient room temperature ethanol sensor device based on p-n homojunction of p-TiO2 nanoparticles (NPs) and n-TiO2 nanotubes (NTs) is reported. p-TiO2 NPs were prepared by low-temperature sol–gel method and coated on n-TiO2 NTs (NPs) grown by electrochemical anodization. Field emission scanning electron microscopy and X-ray diffraction authenticated the formation of stable homojunction between p-type anatase TiO2 NPs and n-type anatase TiO2 NTs. Current–voltage characteristics of the device, in the lower voltage range (0–1.26 V) for 30 °C, followed nonlinear characteristics (Schottky). With increase in voltages (>1.26 V) and temperature (40 °C–100 °C) such nonlinear behavior moves toward more linear ones. The gas sensing performance of the homojunction device was studied at room temperature with alcohols as the test species. The device offered the maximum response magnitude of ～57% (toward ethanol) at 100 ppm with appreciably fast response time and recovery time of ～30 and ～16 s, respectively. Dramatic increase in the effective depletion region area distributed throughout the nanotubular voids and the associated localized electric filed originated from the electrostatic charge separation therein (which helps in easy dissociation of target species) is possibly responsible for such efficient room temperature sensing performance.
关键词： room temperature,Ethanol sensing,fabrication and characterization,p-TiO2 nanoparticles (NPs)/n-TiO2 nanotubes (NTs),homojunction
更新于2025-09-19 17:15:36
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Multi-spectral frequency selective mid-infrared microbolometers
摘要： Frequency selective detection of low energy photons is a scientific challenge using natural materials. A hypothetical surface which functions like a light funnel with very low thermal mass in order to enhance photon collection and suppress background thermal noise is the ideal solution to address both low temperature and frequency selective detection limitations of present detection systems. Here, we present a cavity-coupled quasi-three dimensional plasmonic crystal which induces impedance matching to the free space giving rise to extraordinary transmission through the sub-wavelength aperture array like a 'light funnel' in coupling low energy incident photons resulting in frequency selective perfect (~100%) absorption of the incident radiation and zero back reflection. The peak wavelength of absorption of the incident light is almost independent of the angle of incidence and remains within 20% of its maximum (100%) up to 45°. This perfect absorption results from the incident light-driven localized edge 'micro-plasma' currents on the lossy metallic surfaces. The wide-angle light funneling is validated with experimental measurements. Further, a super-lattice based electronic biasing circuit converts the absorbed narrow linewidth (Δλ/λ ~0.075) photon energy inside the sub-wavelength thick film (< λ/100) to voltage output with high signal to noise ratio close to the theoretical limit. Such artificial plasmonic surfaces enable flexible scaling of light funneling response to any wavelength range by simple dimensional changes paving the path towards room temperature frequency selective low energy photon detection.
关键词： microbolometers,plasmonic crystal,light funnel,perfect absorption,room temperature detection,mid-infrared,frequency selective detection
更新于2025-09-19 17:15:36