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Structural and thermoelectric properties of copper sulphide powders
摘要： Over the past few years, Cu-based materials have been intensively studied focusing on their structural and thermoelectric properties. In this work, copper sulphide powders were synthesized by the sol-gel method. The chemical composition and the morphological properties of the obtained samples were analyzed by X-ray diffraction, differential thermal analysis, and scanning electron microscopy. It is shown that the decomposition from one phase to another can be obtained by annealing. The electrical resistivity and the crystallite size were found to be strongly affected by the phase transition. Thermoelectric analyses showed that the digenite phase exhibits the highest power factor at room temperature. The Seebeck coefficient of the compound Cu1.8S shows a pronounced peak at the γ–β transition temperature. This behavior was statistically explained in terms of a dramatic increase in the disorder in the atoms-carriers ensemble.
关键词： thermoelectricity,copper sulphide,annealing temperature,phase transition
更新于2025-09-23 15:22:29
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Enhanced Ultraviolet Emission from Hydrothermally Grown ZnO Nano-Grass on Si Substrate
摘要： Highly crystalline one-dimensional zinc oxide (ZnO) nano-grass was grown on silicon (Si) substrate by a modified hydrothermal method. A predominantly c-oriented ZnO nano-grass with an average diameter of 40–60 nm and length of 1.5–2.0 lm was obtained. From the photoluminescence (PL) measurement, we observed a defect-free, intense ultraviolet emission of as-grown ZnO nano-grass, confirming the absence of singly ionized oxygen vacancies. The absence of green deep-level emission in the PL spectrum further implies a high crystallinity of as-grown ZnO nano-grass. The high-quality ZnO nano-grass has potential applications in single nanowire-based light-emitting diodes, solar cells, themoresistive sensing, photocatalysis, ultraviolet photodetectors, optical switches, waveguides and nano-lasers.
关键词： photoluminescence,ZnO nanowires,annealing process,ultraviolet emission,hydrothermal method
更新于2025-09-23 15:22:29
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Influence of annealing temperature on photoluminescence of CePO4 thin films on silicon substrates prepared by electron beam evaporation
摘要： Nanostructured CePO4 thin films were prepared on silicon substrates by electron beam evaporation technique. In this work, the effects of annealing temperature on photoluminescence (PL) of CePO4 thin films were investigated. CePO4 thin films were annealed at different temperatures between 700 and 1100 °C for 30 min in nitrogen. The annealed CePO4 films show a strong ultraviolet emission at room temperature. Besides, a violet/blue emission was observed when the annealing temperature reached 1000 °C. The X-ray diffraction results show the monoclinic structure of CePO4 thin films. The scanning electron microscopy images were taken to confirm different crystallinities. The concentration of different elements was determined by energy-dispersive X-ray spectroscopy. The excellent PL emission in the annealed films indicates that the CePO4 thin films could be useful for silicon-based light sources.
关键词： Annealing,CePO4,Thin films,Photoluminescence
更新于2025-09-23 15:22:29
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The influence of Ag doping and annealing on phase, structural and carrier transport characteristics of CIS thin films
摘要： The un-doped and Ag-CIS thin films were deposited on quartz glass substrates by single source thermal evaporation method. Then, some CIS films were annealed in vacuum or N2 atmosphere from 350 °C to 550 °C. The results of XRD patterns showed the phase compositions of CIS thin films were changed with the increase of annealing temperature. Meanwhile, the results of Raman measurement confirmed a dramatic transition from CA phase to CH phase. Furthermore, the Ag atoms could promote the recrystallization process and the transition from CA phase to CH phase, which might result in the improvement of optical-electrical properties of CIS film. The transient photocurrent of the CIS-3 sample annealed at 450 °C was higher than those of other samples, which might be related to the good crystal quality. The results of I-V curves confirmed the N-type conduction of CIS-3 films, which was consistent with the results of EDS measurement. The C-V results of CIS-2 films also were the same as the results of EDS measurement. Furthermore, for the CIS-2 samples, with increase of annealing temperature, the change of conduction type may be related to the S element volatilization under vacuum situation and the decomposition of the substitutional defects AgIn.
关键词： Doping,CIS,Optical-electrical Properties,Photocurrent,Annealing
更新于2025-09-23 15:22:29
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Single photon detection with SiPMs irradiated up to 1014?cm?2 1-MeV-equivalent neutron fluence
摘要： Silicon photomultipliers (SiPM) are solid state light detectors with sensitivity to single photons. Their use in high energy physics experiments, and in particular in ring imaging Cherenkov (RICH) detectors, is hindered by their poor tolerance to radiation. At room temperature the large increase in dark count rate makes single photon detection practically impossible already at 1011 cm?2 1-MeV-equivalent neutron fluence. The neutron fluences foreseen by many subdetectors to be operated at the high luminosity LHC range up to 1014 cm?2 1-MeV-equivalent. In this paper we present the effects of such high neutron fluences on Hamamatsu and SensL SiPMs of different cell size. The advantage of annealing at high temperature (up to 175?C) is discussed. We demonstrate that, after annealing, operation at the single photon level with a SiPM irradiated up to 1014 cm?2 1-MeV-equivalent neutron fluence is possible at cryogenic temperature (77 K) with a dark count rate below 1 kHz.
关键词： Cryogenic temperature,Radiation damage,Single photon detection,SiPM,Neutron irradiation,Annealing
更新于2025-09-23 15:22:29
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The effects of thermal annealing on the structural and electrical properties of Zinc Tin oxide thin films for transparent conducting electrode applications
摘要： The as-deposited and annealed Zinc tin oxide (Zn2SnO4) thin films were deposited by electron beam evaporation technique and were characterized for the structural, optical and electrical properties. The x-ray diffraction technique revealed the amorphous nature of as-deposited thin film while the films annealed at 400, 500 and 6000C in air were found to be polycrystalline. The phase change from amorphous to crystalline Zn2SnO4 results in the higher resistance as revealed by resistance versus temperature measurements. From the Hall Effect, the as deposited film shows the electron mobility and carrier concentrations (electron) equal to 33cm2/V.s and 8.361x 1017cm-3 respectively. The agglomeration of grains in annealed thin films are observed by Atomic Force Microscopy (AFM) technique.The peaks in Optical transmission spectra, observed by using the UV-Vis spectroscopy confirm the creation of sub levels between conduction band minimum and valence band maximum after annealing. The band gaps calculated by Tauc plot explore the possibility of shifting the Fermi level towards valence band maximum after thermal annealing.
关键词： Annealing temperature,Zn2SnO4,Band gap,Oxygen vacancies,Electron beam evaporation,TCOs
更新于2025-09-23 15:22:29
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Reduced Graphene Oxide-Nanostructured Silicon Photosensors With High Photoresponsivity at Room Temperature
摘要： We have created nanostructured Si (~3 nm) with a direct band gap of 1.37 eV on electrically conducting reduced graphene oxide (rGO) for a highly efficient photosensor. This robust photosensor is fabricated using a non-equilibrium processing route, where nanosecond excimer laser pulses melt the alternating layers of Si and amorphous carbon to form micropillars and nanoreceptors of Si on rGO layers. The incident white light generates free carriers in the Si microstructures and nanoreceptors which are ballistically transported (via rGO layers) to the external circuit under the application of a voltage bias. The responsivity of rGO-Si devices to light (resistance vs time) and I-V measurements indicate an exponential drop in resistance with the incidence of white light and non-rectifying nature, respectively. Photoresponsivity of the rGO-Si devices is calculated to be 3.55 A/W at room temperature, which is significantly larger than the previously fabricated graphene-based Ohmic photosensors. Temperature-dependent resistance measurements of rGO-Si structures follow Efros-Shklovoskii variable range hopping (ES-VRH) electrical conduction in the low-temperature region (<100 K) and Arrhenius conduction in the high-temperature region (>100 K). In rGO, the localization length, hopping energy, and activation energy are calculated to be 17.58 μm, 3.15 meV, and 1.67 meV, respectively. The 2D nature of highly reduced and less defective rGO also render an interesting negative magnetoresistance (~2.5 %) at 5 K, thereby indicating potential implications of rGO-Si in opto-spintronics. The large-area integration of rGO-Si structures with sapphire employing nanosecond pulsed laser annealing and its exciting photosensing properties will open a new frontier for further extensive research in these functionalized 2D materials.
关键词： Pulsed laser annealing,Raman spectroscopy,Variable range hopping,Nanostructures,Reduced graphene oxide
更新于2025-09-23 15:22:29
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Multi-layered WO3 nano-platelets for efficient photoelectrochemical water splitting: the role of the annealing ramp
摘要： Multi-layered WO3 nano-square platelets films were successfully grown on transparent TCO substrates by spray-coating of WO3 nanoparticles aqueous suspension prepared by the sol-gel method. This work assesses the influence of two annealing schemes in the photo-response of WO3 photoelectrodes with different film thicknesses. The photoelectrochemical characterization reveals that the slow-heating ramp produces a photoelectrode with an improved photocurrent density of 1.6 mA·cm-2 at 1.23 V vs RHE. Comparing photoelectrodes with the same film thickness, the slow-heating ramp yield higher photocurrent densities; 80 % more than the conventional fast-heating ramp. The effect of the annealing ramp on the morphology and crystalline-phase structure of WO3 photoelectrodes is correlated with the photocurrent density. The slow-heating ramp annealing unveils film morphology with both, higher porosity degree and higher nano-square platelets dimensions. DRX structural analyses disclose that the films grow in monoclinic crystalline phase with a textural preferential direction [002], often related to improved photocurrent performances. The crystallite sizes and lattice microstrain are estimated using a simple X-ray diffraction broadening method, the Williamson-Hall analysis. A quantified correlation between the WO3 lattice defects, intergrains strain and performance is performed. The proposed deposition method paves the way for producing efficient and scalable photoelectrodes of WO3 for photoelectrochemical water splitting by using low-cost and simple manufacturing processes.
关键词： annealing ramp,X-ray peak broadening,tungsten trioxide,nano-platelets,photoelectrochemical cells,photoelectrodes
更新于2025-09-23 15:22:29
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Femtosecond Optical Annealing Induced Polymer Melting and Formation of Solid Droplets
摘要： Interaction between femtosecond laser pulses with polymeric thin films induced transient optical annealing of the polymer molecules. Melting of the polymer films took place during the transient annealing process, so that a solid-liquid-solid phase transition process was observed. Ultrafast cooling of the melting polymer produced solidified droplets. Microscopic and spectroscopic characterization revealed that the polymer molecules were rearranged with preferable H-aggregation to reach the lowest formation energy during the melting process. Intermolecular coupling was enhanced due to the modified molecular arrangement. This observation of melting of polymeric semiconductors due to the interaction with femtosecond light pulses is potentially important for better understanding laser-matter interactions and for exploring organic optoelectronic devices through special material processing.
关键词： transient optical annealing,melting polymer droplets,solid-liquid-solid phase transition,femtosecond laser-matter interaction,molecular rearrangement
更新于2025-09-23 15:22:29
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Uniform Sb <sub/>2</sub> S <sub/>3</sub> optical coatings by chemical spray method
摘要： Antimony sulfide (Sb2S3), an environmentally benign material, has been prepared by various deposition methods for use as a solar absorber due to its direct band gap of ≈1.7 eV and high absorption coefficient in the visible light spectrum (1.8 × 105 cm?1 at 450 nm). Rapid, scalable, economically viable and controllable in-air growth of continuous, uniform, polycrystalline Sb2S3 absorber layers has not yet been accomplished. This could be achieved with chemical spray pyrolysis, a robust chemical method for deposition of thin films. We applied a two-stage process to produce continuous Sb2S3 optical coatings with uniform thickness. First, amorphous Sb2S3 layers, likely forming by 3D Volmer–Weber island growth through a molten phase reaction between SbCl3 and SC(NH2)2, were deposited in air on a glass/ITO/TiO2 substrate by ultrasonic spraying of methanolic Sb/S 1:3 molar ratio solution at 200–210 °C. Second, we produced polycrystalline uniform films of Sb2S3 (Eg 1.8 eV) with a post-deposition thermal treatment of amorphous Sb2S3 layers in vacuum at 170 °C, <4 × 10?6 Torr for 5 minutes. The effects of the deposition temperature, the precursor molar ratio and the thermal treatment temperature on the Sb2S3 layers were investigated using Raman spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and UV–vis–NIR spectroscopy. We demonstrated that Sb2S3 optical coatings with controllable structure, morphology and optical properties can be deposited by ultrasonic spray pyrolysis in air by tuning of the deposition temperature, the Sb/S precursor molar ratio in the spray solution, and the post-deposition treatment temperature.
关键词： vacuum annealing,Volmer–Weber growth,antimony sulfide,thin films,ultrasonic spray
更新于2025-09-23 15:22:29