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Characterizing the electrical breakdown properties of single n-i-n-n <sup>+</sup> :GaN nanowires
摘要： The electrical transport properties and breakdown behaviors of single n-i-n-nt GaN nanowires (NWs) are investigated through in-situ nanoprobing inside a scanning electron microscope (SEM). The nanoprobing contact resistance is dramatically reduced by increasing the Si-doping concentration of the top nt-GaN segment of the NW. The dependence of the NW breakdown parameters (i.e., breakdown voltage, power, and current density) on the nt-GaN Si-doping concentration and the NW diameter is experimentally quanti?ed and explained by the localized thermal decomposition mechanism of the NW. Enabled by the low NW-nanoprobe contact resistance, a breakdown current density of 4.65 MA/cm2 and a breakdown power of 96.84 mW are achieved, both the highest among the previously reported results measured on GaN NWs.
关键词： Si-doping,electrical breakdown,GaN nanowires,thermal decomposition,nanoprobing
更新于2025-09-10 09:29:36
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Phosphorus-doped isotype g-C3N4/g-C3N4: an efficient charge transfer system for photoelectrochemical water oxidation
摘要： Constructing isotype g-C3N4/g-C3N4 heterojunction is an approach to improve the efficiency of g-C3N4 towards solar-assisted oxidation of water. Such functional configuration can effectively overcome the intrinsic drawback of rapid charge recombination of g-C3N4. Here, a modified g-C3N4, with homogeneous phosphorus doping, is prepared in this work through a phosphide-involved gas phase reaction. The resulting P-g-C3N4 displays altered electronic structure, including upshifted band edge potential, narrowed band gap and improved electronic conductivity. These features allow P-g-C3N4 as an outstanding candidate to form isotype junction with pristine g-C3N4. As expected, the accelerated charge separation and migration in target junction is validated by various measurements. The isotype g-C3N4/P-g-C3N4 heterojunction achieves a optimized photocurrent as high as 0.3 mA·cm-2 at 1.23 V vs RHE (AM 1.5G, 100 mW·cm-2), representing 8-fold’s enhancement compared with pristine g-C3N4. The present strategy for constructing g-C3N4-based isotype heterojunction networks is found effective for large-scale manufacturing.
关键词： phosphorus doping,g-C3N4,charge transfer,isotype heterojunction,photoelectrochemical
更新于2025-09-10 09:29:36
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Molecular adsorption and strain-induced ferromagnetic semiconductor-metal transition in half-hydrogenated germanene
摘要： Very recently, half-hydrogenated germanene has been achieved in an experiment. In this paper, we investigate the effects of tetracyanoquinodimethane (TCNQ) molecular adsorption and strain on the electronic properties of half-hydrogenated germanene through first-principles. As an electron-acceptor molecule, TCNQ is exploited to non-covalently functionalize the half-hydrogenated germanene. However, this physical adsorption induces a ferromagnetic semiconductor–metal transition in half-hydrogenated germanene due to charge transfer from the substrate to the TCNQ molecule. More importantly, the superstructure of half-hydrogenated germanene/TCNQ is extremely sensitive to biaxial tensile strain. Under the biaxial tensile strain of 0.25%, the ferromagnetic semiconductor–metal transition induced by molecular adsorption can surprisingly be overturned. Meanwhile, a strong p-type doping is exhibited. Remarkably, it would return from a ferromagnetic semiconductor to a metal again when the biaxial tensile strain increases to 1.5%. Our analysis based on the structural and electronic properties of half-hydrogenated germanene/TCNQ indicates that such metal–semiconductor–metal transition in half-hydrogenated germanene/TCNQ under biaxial tensile strain may originate from the strong local deformation, resulting in the energy of the valence band maximum decreasing below or increasing above the Fermi level.
关键词： ferromagnetic semiconductor–metal transition,p-type doping,half-hydrogenated germanene,TCNQ molecular adsorption,biaxial tensile strain
更新于2025-09-10 09:29:36
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Photocatalytic and Antibacterial Activities of Silver and Iron Doped Titania Nanoparticles in Solution and Polyaspartic Coatings
摘要： Visible region active photocatalytic coatings are of interest for antimicrobial activity in low light applications or those employing LED lights with limited UV content. This work examined Ag and Fe doped titania nanoparticles (nTiO2) with varying dopant ranges in polyaspartic polymer coatings for potential light and dark activity. First, the Ag and Fe doped nTiO2 were synthesized by sol-gel chemistry with varying dopant concentrations, then characterized with respect to their size and aggregate size distribution, crystallinity, and surface and band gap features. The photocatalytic activity was then tested with methylene blue (MB) under both AM1.5G and visible light. From both sample sets (Ag and Fe doped nTiO2), the best photo catalytically active sample materials were chosen for antibacterial tests with gram negative Escherichia coli (E. coli) and gram positive Bacillus subtilis (B. subtilis) in (a) solution and (b) polyaspartic nanocomposites under UV and visible irradiation. The results showed that Ag doped nTiO2 samples delivered the best photocatalytic activity and excellent antibacterial action, even in the dark, attributed to both an enhanced band gap and surface area, as well as a combination of photocatalytic activity and Ag being present at the nanoparticle’s (NP) surface. No leaching of Ag at room temperature was observed from the nTiO2 structure, giving potential for next generation coatings that are both light and dark active.
关键词： Fe doping,polyaspartic composites,antibacterial activity,photo-catalysis,Ag doping,nanoparticles,Titania
更新于2025-09-09 09:28:46
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Thermal Treatments and Photoluminescence Properties of ZnO and ZnO:Yb Films Grown by Magnetron Sputtering
摘要： This work is on ZnO and ZnO:Yb (0.3 at%) films prepared on (100) Si substrates by magnetron sputtering and deals with their structural and photoluminescence evolutions upon annealing at different temperatures from 873 to 1173 K during 1 h under N2 atmosphere. The microstructural characterizations reveal that, for both sample series, annealing treatment improves the crystallinity of ZnO of the upper part of the films. However, (002) textured ZnO columnar growth is only observed for ZnO films. For annealing temperatures higher than 973 K, rare earth and Si diffusions toward the film/substrate interface are observed resulting in the appearance of a zinc silicate phase for ZnO films and a composite material made of nanoscale ZnO grains surrounded by an amorphous phase for ZnO:Yb films. In addition, photoluminescence measurements show that Yb doping in ZnO results in a lower integrated photoluminescence intensity compared to that of ZnO films and the photoluminescence response in the visible spectral range is also modified most probably due to the presence of dopant. Furthermore, the PL intensity at 980 nm originating from electronic transitions between 2F5/2 and 2F7/2 levels of Yb3+ ion increased with temperature. At last, the evolutions of the PL emissions with temperature from the ZnO defects are discussed.
关键词： ZnO,thin film,magnetron sputtering,Yb doping
更新于2025-09-09 09:28:46
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High-Temperature Cs <sub/>x</sub> C <sub/>58</sub> Fullerides
摘要： Cs doped non-IPR fullerides have been grown by co-depositing C58 cations and Cs atoms on HOPG. The C58 cages, as building blocks of the material, form a predominantly covalently stabilized scaffold, C58–C58, which is doped by Cs atoms thermally diffusing across the bulk. The heating of the solid CsxC58 sample is accompanied by sublimation of Cs, C58, and C60 species from the topmost layers of the sample. However, the major part (>94%) of the material survives the heating procedure and constitutes a doped high-temperature carbon solid, HT-CsxC58. The new non-IPR material exhibits surprisingly high thermal stability. It survives a heating flash up to 1100 K at which the classic IPR-CsxC60 phase does not exist anymore. However, the thermally treated HT-CsxC58 phase exhibits a considerably depleted Cs content (x < 2) and a significantly modified carbon scaffold. The apparent stability of the scaffold results from covalent C–C bonds interlinking adjacent carbon cages. Cs atoms in the HT-CsxC58 phase contribute to this stability only as minority species, forming comparably weak ionic bonds with C58–C58 oligomers. However, this interaction facilitates the formation of structural defects (new non-IPR sites) in carbon cages. The surface topography of the HT-CsxC58 as monitored by SPEM, AFM, and SEM is governed by islands standing out by their elevated Cs/C ratio.
关键词： X-ray photoelectron spectroscopy,fullerenes,desorption,isolated pentagon rule,cesium doping
更新于2025-09-09 09:28:46
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The Study of Features of Formation and Properties of A3B5 Semiconductors Highly Doped with Iron
摘要： Layers of InAs, InSb, and GaSb semiconductors highly doped with iron during their growth by the method of pulsed laser deposition are studied experimentally. The best temperatures for layer formation on GaAs (100) substrates are: 250°C (InSb : Fe), 300°C (InAs : Fe), and 350°C (GaSb : Fe). At high Fe concentration (over 10 at %) the layers display ferromagnetic properties expressed in emergence of a hysteresis curve within the magnetic field dependences of the Hall resistance, negative magnetoresistance, and in some cases, ferromagnetic-type magnetization at measurements at room temperature. The atoms of iron do not change the type of layer conductivity; InAs : Fe and InSb : Fe layers possess n-type conductivity, and GaSb : Fe layers display p-type conductivity due to their intrinsic point defects.
关键词： Hall effect,A3B5 semiconductors,ferromagnetic properties,magnetoresistance,iron doping,pulsed laser deposition
更新于2025-09-09 09:28:46
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Probing the nanoscale origin of strain and doping in graphene-hBN heterostructures
摘要： We use confocal Raman microscopy and a recently proposed vector analysis scheme to investigate the nanoscale origin of strain and carrier concentration in exfoliated graphene-hexagonal boron nitride (hBN) heterostructures on silicon dioxide (SiO2). Two types of heterostructures are studied: graphene on SiO2 partially covered by hBN, and graphene fully encapsulated between two hBN flakes. We extend the vector analysis method to produce separated spatial maps of the strain and doping variation across the heterostructures. This allows us to visualise and directly quantify the much-speculated effect of the environment on carrier concentration in graphene. Moreover, we demonstrate that variations in strain and carrier concentration in graphene arise from nanoscale features of the heterostructures such as fractures, folds and bubbles trapped between layers. For bubbles in hBN-encapsulated graphene, hydrostatic strain is shown to be greatest at bubble centres, whereas the maximum carrier concentration is localised at bubble edges. Raman spectroscopy is shown to be a non-invasive tool for probing strain and doping in graphene, which could prove useful for engineering of two-dimensional devices.
关键词： hexagonal boron nitride,Raman,strain,van der Waals heterostructures,graphene,hBN,doping
更新于2025-09-09 09:28:46
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Semiconducting Cu-doped AlO<sub>x</sub> films fabricated by drop-photochemical deposition
摘要： Cu-doped aluminum oxides (AlOx) thin films were deposited by the drop photochemical deposition method using an aqueous solution containing Al(NO3)3, Cu(NO3)2 and Na2S2O3. After deposition, the films were annealed at 400oC for 60 min. The Cu-doped AlOx films showed p-type photoresponse in a photoelectrochemical measurement. Moreover, while negligible electrical conductivity was detected for non-doped AlOx on an insulating substrate, electrical conduction was clearly observed for the Cu-doped films with resistivity of the order of 108 Ωcm. The junction between non-doped AlOx and Cu-doped AlOx showed rectification and thus was considered to be a p-n junction. Thus, the conductivity and conduction type of aluminum oxide was controlled by Cu doping.
关键词： p-n junction,photochemical deposition,semiconductor,Cu doping,Aluminum oxide
更新于2025-09-09 09:28:46
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The Role of Weak Molecular Dopants in Enhancing the Performance of Solution-Processed Organic Field-Effect Transistors
摘要： Molecular doping is an effective method to enhance the charge carrier density for reducing the contact resistance and improving the charge mobility in organic field-effect transistors (OFETs). Previous reports mainly focus on the strong dopants with the EAdopant > IEOSC (p-type) or IEdopant < EAOSC (n-type) to enable the efficient charge transfer (EA: electron affinity; IE: ionization energy; OSC: organic semiconductor). However, the effects of weak dopants on the OFET performance of OSC are rarely investigated. Thus, in this study, it is demonstrated that two new fluorinated compounds (Tetrafluorophthalonitrile (TFP) and Octafluoronaphthalene (OFN)) can act as weak dopants in thin film of TIPS-Pentacene (TIPS). Although they exhibit unmatched EAs (3.45 eV for TFP and 3.44 eV for OFN) compared to the IE (5.17 eV) of the host TIPS, they still can fulfill the p-type doping with the OSC matrix. Systematic structural and electrical characterization reveals the important role of the formed charge-transfer interaction and the improved crystallinity in enhancing the carrier mobility. The doped poly(3-hexylthiophene) is also investigated to confirm the universality of the weak dopants. The study should provide a new thought for the exploitation of novel planar soluble weak dopants in OFETs.
关键词： solution-processed organic field-effect transistors,molecular doping,weak dopants
更新于2025-09-09 09:28:46