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Self-assembled line network in BiFeO3 thin films
摘要： In this work we report on the controlled fabrication of a self-assembled line network in highly epitaxial BiFeO3 thin films on top of LaAlO3 in the kinetically limited grown region by RF sputtering. As previously shown in the case of manganite thin films, the remarkable degree of ordering is achieved using vicinal substrates with well-defined step-terrace morphology. Nanostructured BiFeO3 thin films show mixed-phase morphology. Besides typical formation following (100) and (010) axes, some mixed phase nanodomains are detected also in-between the regular line network. These particular microstructures open a playground for future applications in multiferroic nanomaterials.
关键词： Mixed phase nanodomains,Long-range ordered nanostructures,Multiferroic thin films,Growth kinetic
更新于2025-09-23 15:19:57
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Investigation of boron-doped hydrogenated silicon films as a thermo-sensing layer for uncooled microbolometer
摘要： Boron-doped hydrogenated silicon films are used in thermo-sensing layer in infrared detectors or uncooled microbolometers. Among thermo-sensing materials such as vanadium oxide and amorphous silicon and silicon diodes, amorphous silicon is the most common. Parameters such as the temperature coefficient of resistance (TCR), sheet resistance and 1/f noise are very important for the performance of these devices. One thermo-sensing material in particular, boron-doped hydrogenated silicon (BSi:H), has satisfactory TCR, sheet resistance (Rsheet), and 1/f noise values. The BSi:H films are deposited using radio frequency plasma-enhanced chemical vapor deposition. The dependence of electrical, structural, and chemical properties of the BSi:H films on the plasma parameters is reported. The TCR of the films is 1.0 - 2.9 %/K, Rsheet is 1.2 - 37.8 MΩ/□ and crystalline volume fraction is 10.2 - 68.5%. The properties of the amorphous and mixed-phase are compared. It is found that the 1/f noise of the mixed-phase film is lower than that of the amorphous phase film. These results show that the boron doped mixed-phase silicon films are suitable for use as thermo-sensing layers.
关键词： mixed-phase,thermo-sensing layer,uncooled microbolometer,boron-doped hydrogenated silicon films
更新于2025-09-16 10:30:52
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Phase-junction design of MOF-derived TiO2 photoanodes sensitized with Quantum Dots for efficient hydrogen generation
摘要： Photoelectrochemical (PEC) water splitting is a promising and environmentally friendly pathway for exploiting renewable energy sources, to address the ever-growing demand for clean energy. Due to its excellent photostability and favorable band alignment, titanium dioxide (TiO2) is the one of the most common metal oxide for water splitting. However, the efficiency in TiO2-based PEC systems is limited by the high recombination of photo-generated electron/hole pairs and large intrinsic band gap (3.2 eV) which limit the absorption of the sunlight. Herein, we explore a simple metal organic framework (MOF)-derived synthesis to obtain a controlled mixed-phase (anatase and rutile) of TiO2 nanoparticles, which retain the MOF crystal morphology. Compared with commercial TiO2 films, the MOF-derived TiO2 film sensitized by core-shell CdSe@CdS QDs, showed an enhanced PEC device stability of +42.1% and PEC performance of +47.6%. The enhanced performance is due to the presence of the mixed rutile/anatase phases, that creates a favorable band energy alignment for the separation of the photogenerated charges. The proposed MOF-derived TiO2 is an efficient strategy to improve the efficiency of the TiO2-QDs heterojunction based PEC system for hydrogen generation.
关键词： Metal organic framework,Mixed-phase TiO2,Photoelectrochemical water splitting,Quantum dots,Hydrogen generation
更新于2025-09-11 14:15:04
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An improved algorithm for polar cloud-base detection by ceilometer over the ice sheets
摘要： Optically thin ice and mixed-phase clouds play an important role in polar regions due to their effect on cloud radiative impact and precipitation. Cloud-base heights can be detected by ceilometers, low-power backscatter lidars that run continuously and therefore have the potential to provide basic cloud statistics including cloud frequency, base height and vertical structure. The standard cloud-base detection algorithms of ceilometers are designed to detect optically thick liquid-containing clouds, while the detection of thin ice clouds requires an alternative approach. This paper presents the polar threshold (PT) algorithm that was developed to be sensitive to optically thin hydrometeor layers (minimum optical depth τ ≥ 0.01). The PT algorithm detects the first hydrometeor layer in a vertical attenuated backscatter profile exceeding a predefined threshold in combination with noise reduction and averaging procedures. The optimal backscatter threshold of 3 × 10?4 km?1 sr?1 for cloud-base detection near the surface was derived based on a sensitivity analysis using data from Princess Elisabeth, Antarctica and Summit, Greenland. At higher altitudes where the average noise level is higher than the backscatter threshold, the PT algorithm becomes signal-to-noise ratio driven. The algorithm defines cloudy conditions as any atmospheric profile containing a hydrometeor layer at least 90 m thick. A comparison with relative humidity measurements from radiosondes at Summit illustrates the algorithm's ability to significantly discriminate between clear-sky and cloudy conditions. Analysis of the cloud statistics derived from the PT algorithm indicates a year-round monthly mean cloud cover fraction of 72 % (±10 %) at Summit without a seasonal cycle. The occurrence of optically thick layers, indicating the presence of supercooled liquid water droplets, shows a seasonal cycle at Summit with a monthly mean summer peak of 40 % (±4 %). The monthly mean cloud occurrence frequency in summer at Princess Elisabeth is 46 % (±5 %), which reduces to 12 % (±2.5 %) for supercooled liquid cloud layers. Our analyses furthermore illustrate the importance of optically thin hydrometeor layers located near the surface for both sites, with 87 % of all detections below 500 m for Summit and 80 % below 2 km for Princess Elisabeth. These results have implications for using satellite-based remotely sensed cloud observations, like CloudSat that may be insensitive for hydrometeors near the surface. The decrease of sensitivity with height, which is an inherent limitation of the ceilometer, does not have a significant impact on our results. This study highlights the potential of the PT algorithm to extract information in polar regions from various hydrometeor layers using measurements by the robust and relatively low-cost ceilometer instrument.
关键词： optically thin ice clouds,cloud-base detection,polar regions,mixed-phase clouds,ceilometer
更新于2025-09-10 09:29:36
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Facile ionothermal synthesis of TiO2 nanorods for photocatalytic H2 generation
摘要： Facile ionothermal method has been employed to synthesize One-dimensional (1-D) mixed phase TiO2 nanorods (NRs) using ionic liquid as the reaction medium. The PXRD pattern reveals the formation of mixed phase TiO2 having 68.3% of anatase and 31.7% rutile phase with average crystallite size of ~ 10?nm. TEM images depict the average thickness of TiO2 NRs are in the range 50–100?nm. The 1-D mixed phase TiO2 NRs showed 5 times better hydrogen production activity than P-25 in the water-glycerol mixture under solar light irradiation. The reason could be the synergetic effect and unique optical properties of 1-D anatase–rutile TiO2 mixed-phase system.
关键词： solar light irradiation,TiO2 nanorods,mixed phase,ionothermal synthesis,photocatalytic H2 generation
更新于2025-09-10 09:29:36
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Comparative study of photoluminescence of single and mixed phase ZrTiO4 prepared by solution combustion and polymeric precursor method
摘要： This work aims to study synthesis methods and photoluminescence properties of ZrTiO4. Wet chemical routes used for synthesis are solution combustion method and polymeric precursor method. Urea and glycine are two different fuels used in solution combustion synthesis. Scanning Electron Microscope studies con?rms that morphology of the nanoparticles depends on synthesis method. Photoluminescent property depends on the phase of the material, rather than the method of synthesis. Characterization such as X-ray diffraction, SEM, Re?ectance and Photoluminescence studies prove the role of synthesis methods on the properties of the ZrTiO4. Both upconversion and down conversion luminescence have been achieved by synthesizing ZrTiO4 from solution combustion method using urea as fuel, where ZrTiO4 exists in mixed phase.
关键词： Polymeric precursor method, (PPM),Photoluminescence,Single phase,Mixed phase,ZrTiO4,Solution combustion method, (SCS)
更新于2025-09-09 09:28:46
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PHIPS–HALO: the airborne Particle Habit Imaging and Polar Scattering probe – Part 1: Design and operation
摘要： The number and shape of ice crystals present in mixed-phase and ice clouds influence the radiation properties, precipitation occurrence and lifetime of these clouds. Since clouds play a major role in the climate system, influencing the energy budget by scattering sunlight and absorbing heat radiation from the earth, it is necessary to investigate the optical and microphysical properties of cloud particles particularly in situ. The relationship between the microphysics and the single scattering properties of cloud particles is usually obtained by modelling the optical scattering properties from in situ measurements of ice crystal size distributions. The measured size distribution and the assumed particle shape might be erroneous in case of non-spherical ice particles. There is a demand to obtain both information correspondently and simultaneously for individual cloud particles in their natural environment. For evaluating the average scattering phase function as a function of ice particle habit and crystal complexity, in situ measurements are required. To this end we have developed a novel airborne optical sensor (PHIPS-HALO) to measure the optical properties and the corresponding microphysical parameters of individual cloud particles simultaneously. PHIPS-HALO has been tested in the AIDA cloud simulation chamber and deployed in mountain stations as well as research aircraft (HALO and Polar 6). It is a successive version of the laboratory prototype instrument PHIPS-AIDA. In this paper we present the detailed design of PHIPS-HALO, including the detection mechanism, optical design, mechanical construction and aerodynamic characterization.
关键词： mixed-phase clouds,PHIPS-HALO,precipitation,ice crystals,ice clouds,optical properties,radiation properties,climate system,microphysical properties,airborne optical sensor
更新于2025-09-04 15:30:14