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Annealing of Gadolinium-Doped Ceria (GDC) Films Produced by the Aerosol Deposition Method
摘要： Solid oxide fuel cells need a diffusion barrier layer to protect the zirconia-based electrolyte if a cobalt-containing cathode material like lanthanum strontium cobalt ferrite (LSCF) is used. This protective layer must prevent the direct contact and interdiffusion of both components while still retaining the oxygen ion transport. Gadolinium-doped ceria (GDC) meets these requirements. However, for a favorable cell performance, oxide ion conducting films that are thin yet dense are required. Films with a thickness in the sub-micrometer to micrometer range were produced by the dry room temperature spray-coating technique, aerosol deposition. Since commercially available GDC powders are usually optimized for the sintering of screen printed films or pressed bulk samples, their particle morphology is nanocrystalline with a high surface area that is not suitable for aerosol deposition. Therefore, different thermal and mechanical powder pretreatment procedures were investigated and linked to the morphology and integrity of the sprayed films. Only if a suitable pretreatment was conducted, dense and well-adhering GDC films were deposited. Otherwise, low-strength films were formed. The ionic conductivity of the resulting dense films was characterized by impedance spectroscopy between 300 ?C and 1000 ?C upon heating and cooling. A mild annealing occurred up to 900 ?C during first heating that slightly increased the electric conductivity of GDC films formed by aerosol deposition.
关键词： room temperature impact consolidation (RTIC),crystallite size,dense films,thermal powder treatment,electrical conductivity
更新于2025-09-23 15:21:01
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Effects of Parasitic Region in SiC Bipolar Junction Transistors on Forced Current Gain
摘要： Effects of a parasitic region in SiC BJTs on conductivity modulation and a forced current gain (????) were investigated by using TCAD simulation with various device structures. By introducing an Al+-implanted region below the base parasitic region, ???? can be improved because the implanted region can reduce the base spreading resistance, leading to alleviation of debiasing effect. ???? in devices with various parasitic areas, whose base spreading resistances were reduced by the Al+-implantation, were compared. We found that ???? can be enhanced by expanding the parasitic area if the base spreading resistance is sufficiently reduced. The higher ???? is attributed to an expanded conductivity-modulated region. The collector current spreading in the collector layer and hole injection from the parasitic region as well as from the intrinsic region can play a role to evoke conductivity modulation. Thus, the larger parasitic region can expand the conductivity-modulated region, which results in expansion of an active area and the enhancement of ????, though a higher base voltage is required.
关键词： forced current gain,conductivity modulation,parasitic region,hole injection,SiC BJT,base spreading resistance
更新于2025-09-23 15:21:01
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Fabrication of virus metal hybrid nanomaterials: An ideal reference for bio semiconductor
摘要： Recently, Nanotechnology has made easier utilizing plant pathogens as a potential nano-material in biomedical applications. In this research work, we have exploited a devastating plant pathogenic virus of Squash leaf curl China virus (SLCCNV), as a nano-bio template (32 nm) to fabricate the gold and silver nanomaterials. This is achieved through the direct exposure of SLCCNV to gold chloride (HAuCl4) and silver nitrate (AgNO3) precursors at sunlight, resulted into SLCCNV-metallic-hybrid nanomaterials which are synthesized quick ((cid:1)5 min) and eco-friendly. However, virus hybrid nanomaterials are fabricated through the nucleation and growth of metal precursors over the pH-activated capsid of SLCCNV. Under the controlled fabrication process, it produced a highly arrayed virus-metallic-hybrid nanomaterial at nanoscale size limit. Its properties are thoroughly studied through spectroscopic techniques (UV–Vis, DLS, Raman) and electron microscopy (HRTEM & FESEM). In a follow-up study of cytotoxicity assay, the virus and its fabricated nanomaterials show better biocompatibility features even at high concentrations. Finally, the electrical conductivities of virus-metallic-hybrid nanomaterials (Au & Ag) are determined by simple ‘‘lab on a chip” system and Keithley’s pico-ammeter. The result of electrical conductivity measurement revealed that hybrid nanomaterials have greater electrical conductive properties within the band-gap of semi-conductive materials. It is truly remarkable that a plant virus associated metal nanomaterials can be ef?ciently used as bio-semi-conductors which are the ideal one for biomedical applications.
关键词： Virus hybrid nanomaterials,Electrical conductivity,Virus template,Virus nanotechnology,Biocompatibility,Surface biomineralization
更新于2025-09-23 15:21:01
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A field study on the application of distributed temperature sensing technology in thermal response tests for borehole heat exchangers
摘要： Although the enhanced thermal response test (ETRT) method has been used to determine the distribution of ground temperatures and effective thermal conductivities, there are a number of obstacles which limit the wide application of this technology in the discipline of geoengineering. In this literature, four aspects of ETRT technology were investigated: (a) acquisition of ground temperature, (b) installation of the heat exchange tubes, (c) optimization of the monitoring positions, and (d) the difference in thermal conductivity obtained by the ETRT and numerical simulation. To investigate these issues, a field trial was carried out in Heze, Shandong Province, China, and the corresponding numerical models were built. The results demonstrate that: (i) the conventional methods that infer undisturbed ground temperature using water in tubes have large errors, whereas the distributed temperature sensing (DTS) technique enables the measurement of precise temperature profiles; (ii) the thermal conductivity measured using double U-tubes reflects the soil thermal property more accurately than that for a single U-tube; (iii) it is more reasonable to install optical fibers outside the U-tube sidewall than inside the observation tube; and (iv) it is essential to quantitatively consider various interface thermal impedance when estimating ground thermal conductivities using numerical simulation.
关键词： Fiber optic sensor,Distributed temperature sensing (DTS),Ground-coupled heat pump (GCHP),Thermal conductivity,Thermal response test (TRT)
更新于2025-09-23 15:21:01
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Study and Calculation Electrical Properties of Silver Thin Layers by Four- Point Probe Method
摘要： In this research Ag thin layers on silicon p-type substrate with crystal orientation (100) and 300, 360 and 400 nm thicknesses by thermal evaporation was deposited. Four-point probe and XRD analysis of surface layers consequently for study electrical properties included of sheet resistance, conductivity, resistivity and investigation of Ag phase formed, was done. As result XRD was shown that at 400 nm the best state of silver face-central cubic (FCC) structure with crystal orientation (200) was formed and by Deby-Scherrer formula distance between successive plates was calculated 8.94 nm. Four-point illustrated that sheet resistance and electrical resistivity with increase thickness, decreases while conductance increases. At 400 nm thickness Ag layer has the most conductivity and the lowest resistance.
关键词： FCC lattice,Thickness,Sheet Resistance,Conductivity
更新于2025-09-23 15:21:01
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Probing of Thermal Transport in 50-nm Thick PbTe Nanocrystal Film by Time-Domain Thermoreflectance
摘要： Bottom-up fabrication of thermoelectric (TE) materials from colloidal nanocrystal (NC) building blocks can substantially increase their TE efficiency, e.g., by reducing lattice thermal conductivity. In this work, 10-nm spherical phase-pure oleate-capped PbTe NCs with narrow size distribution were synthesized and employed to fabricate 50-nm thick films on insulating SiO2/Si substrates. The spin-coating, with subsequent ligand exchange procedure, was applied to enhance coupling interactions between the NCs. Using dark conductivity measurements, we confirmed the semiconducting behavior and the Schottky-type electrical field-dependent conductivity mechanism in the resultant thin films. The thermal transport in the thin-film was probed by means of a time-domain thermoreflectance (TDTR) method. For this purpose, we used a customized state-of-the-art system based on a picosecond thermoreflectance instrument, which enables area-selective analysis with spatial resolution down to 5 μm. The results show that as-fabricated PbTe NC films exhibit ultralow thermal conductivity of 0.9 W m–1 K–1 at 300 K. The transport property findings suggest potential in the proposed quick and cost-effective spin-coating strategy for bottom-up fabrication of nanostructured TE films from high-quality colloidal NC building blocks.
关键词： colloidal nanocrystals,spin-coating,thermoelectric materials,thermal conductivity,time-domain thermoreflectance,PbTe
更新于2025-09-23 15:21:01
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Intrinsic Sub-Nanocrystalline Silicon Thin Films: Active Layer for Solar Cells
摘要： The study presents the typical aspects of silicon thin films in terms of growth under variation of applied power using Radio frequency Plasma Enhanced Chemical Vapor Deposition technique (RF-PECVD). The corresponding material found to maintain the typical properties of amorphous nature without compensating the structural modification in terms of crystallinity and has been defined as a material having the “sub-nanocrystalline phase”. Characterizations like, UV-Visible spectroscopy, Photoluminescence and Temperature dependent conductivity was used to effectively map the structural details along with electrical and optical properties. The optical bandgap of the films found to be vary from 1.77 eV to 1.99 eV with typical photoresponse variations in the range 103 to 101. At 30 W applied power, the transition regime observed with the formation of sub-nanocrystallites. The analysis of such phase reveals the superior optoelectronic properties. This article suggests the suitability of sub-nanocrystalline silicon thin films to replace hydrogenated amorphous silicon in various applications.
关键词： Nc-Si:H/μc-Si:H,Thin film,PECVD,Sub-nanocrystalline phase,Conductivity
更新于2025-09-23 15:19:57
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Wet Chemical Synthesis of Entangled Nano-fibrous Conducting Polyaniline (PANI) Mesh: Effect of Heating and Stirring
摘要： An effect of heating and stirring in a facile wet chemical route to synthesize entangled nano-fibrous mesh of doped polyaniline (PANI) was reported. The structural, morphological, and optical properties of PANI nano-fibers were found to be dependent on synthesis temperature and stirring. The XRD analysis confirms nano PANI formation with 2θ peaks around 15°, 21°, and 25° for (011), (020), and (200) crystal planes, respectively. The average crystallite size varies between 25 nm to 60 nm due to change in synthesis conditions. The SEM analysis reveals the clustered granule formation for PANI sample synthesized at 28 and 60 ℃ under continuous stirring, whereas, unstirred synthesis at 60 ℃ shows entangled nano-fibrous mesh morphology. The TGA study shows better thermal stability for PANI mesh over granular PANI. The FTIR spectra validates the emeraldine salt PANI formation with peaks corresponding to C-H, C-N, N=Q=N, N=B=N, and N-H vibration bands. The UV-Vis analysis shows the major absorbance peaks around λ: 340 nm (π- π* transition of benzenoid ring), and λ: 800 nm (π- π*, polaron-π* transitions). The dense entangled nano-fibrous coating of PANI synthesized at 60 ℃ without stirring shows highest electrical conductivity of 3.79 S·cm-1.
关键词： polyaniline,optical property,nano-fibrous mesh,electrical conductivity
更新于2025-09-23 15:19:57
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Improving light harvesting and charge extraction of polymer solar cells upon buffer layer doping
摘要： It is an important strategy to improve the performance of polymer solar cells (PSCs) by incorporating metal nanoparticles into functional layers. Herein, gold (Au)@titanium dioxide (TiO2) plasmonic core-shell nanoparticles (PCSNPs) are synthesized and doped into zinc oxide (ZnO) as hybrid electron transport layer in PSCs. Improved light trapping and electrical conductivity are achieved through localized surface plasma resonance of Au@TiO2 PCSNPs. As a result, the short-circuit current density is apparently enhanced, while remaining the unchanged open-circuit voltage. The maximum PCE of 8.801% is obtained when 1.5 wt% Au@TiO2 PCSNPs are introduced into the ZnO layer. This study provides a new inspiration for the development of high efficiency PSCs.
关键词： Surface plasmon resonance,charge transport,Au@TiO2 PCSNPs,Light trapping,Electrical conductivity
更新于2025-09-23 15:19:57
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A Preliminary result on the rGO functionalization as counter-electrode in dye-sensitized solar cells (DSSC)
摘要： In the effort of replacing Platinum (Pt) based counter-electrode (CE) for reducing fabrication cost in the dye-sensitized solar cell (DSSC), we synthesized rGO powder from graphite bar (commercially available) using modified Hummer’s method with an introduction of microwave irradiation. rGO was attached to the FTO surface by dissolving it in the solvent with the addition of ethyl cellulose (ES) following by two-step annealing process. rGO solution was deposited by spin coating technique with different thickness namely 1 layer rGO (A1), 5 layer rGO (A2), 10 layer rGO (A3) and 15 layer rGO (A4) followed by an annealing process, and the reference cell was assigned as A5 (using Pt). From the thin film resistance measurement using the four-probe method and conductivity calculation, the conductivity decreased as the rGO layer becomes thicker, namely from (0.58 to 0.42, 0.07 and 0.03) S/cm for A1, A2, A3, and A4 in consecutive order. From the photovoltaic measurement, we found that the utilization of rGO as a catalyst in CE increased the efficiency of the cell from 3.82% (A5) to 4.52% (A1). Furthermore, increasing the thickness of rGO layer from A1 (2.1 μm) to A2 (10.5 μm) also increased the efficiency from 4.52% to 5.89%, further increasing on the layer thickness A3 (21 μm) to A4 (31.5 μm) reduced the conversion efficiency to 2.57% and 0.33%. The highest conversion efficiency achieved for the cell with 10.5 μm thickness of CE, specifically A2. Further investigation of the influence of CE thickness and conductivity to the internal parameters of the DSSC must be done in order to gain a much better understanding of this result.
关键词： rGO,conductivity,photovoltaic measurement,DSSC,counter-electrode
更新于2025-09-23 15:19:57