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Significant enhancement of photoactivity in one-dimensional TiO2 nanorods modified by S-, N-, O-doped carbon nanosheets
摘要： Titanium dioxide (TiO2) represents one of the most active photocatalysts among metal oxides for the degradation of pollutants and for solar water splitting to produce hydrogen. The most critical drawbacks hindering its broad practical use are the absorption majorly in the UV part of solar spectrum and slow charge dynamics. Combination of TiO2 with a suitable partner in a hybrid nanostructure can effectively address these drawbacks. Here we report a novel nanocomposite system based on one-dimensional TiO2 nanorods wrapped with a sulfur-, nitrogen-, and oxygen-doped carbon (SNOC) nanosheets. The SNOC nanosheets are synthesized by a cost-effective and facile route using eco-friendly carrageenan as a sulfur, oxygen, and carbon source and urea as a nitrogen source. Silica was used as the templating agent that leads to large surface area materials after its removal at the end of the synthesis. Therefore, the synthesized material exhibits superior photocatalytic performance for decoloring representative Rhodamine B (RhB) under visible light irradiation. SNOC shows the apparent rate constant of 7.6 × 10–3 min–1, which is almost 3 times higher than that of a SNOC material without using silica (2.8 × 10–3 min–1). This performance of doped carbon material can be assigned to the effect of large surface area and effective visible light adsorption. The TiO2 NRs / SNOC nanocomposite was investigated for photoelectrochemical water splitting showing much higher photocurrent densities (0.85 mA cm–2) than pure TiO2 nanorod arrays (0.35 mA cm–2), which was due to significant improvement in the charge transfer dynamics and co-catalytic effect of SNOC. All the materials prepared were evaluated on the basis of physical properties such as crystalline structure, optical absorption, surface topography, and electronic properties.
关键词： Water splitting,Photoelectrochemistry,Photocatalysis,Heterojunction,TiO2 nanorods,S, N, O-doped mesoporous carbon
更新于2025-09-23 15:23:52
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Red-light Emission of Li-doped Ga2O3 One-dimensional Nanostructures and the Luminescence Mechanism
摘要： Li-doped Ga2O3 one-dimensional nanostructures were synthesized by thermal evaporation. The observation results of morphology show that there are plenty of one-dimensional nanostructures in the sample. Raman spectra of samples show excellent crystallinity and the Raman peaks of the Li-doped Ga2O3 have red-shifted compared to the “undoped” Ga2O3 in the low wavenumber section. Comparing the photoluminescence behavior of the two samples at room temperature, they were found to have blue light emission peaks, but the emission peak of Li-doped Ga2O3 is blue-shifted. Additionally, there is a strong red light emission peak centered at 692 nm in the spectrum of Li-doped Ga2O3.
关键词： Li-doped,Nanostructures,Photoluminescence,Ga2O3,Raman spectrum
更新于2025-09-23 15:23:52
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Vertical GaN Schottky barrier diodes on Ge-doped free-standing GaN substrates
摘要： Vertical GaN Schottky barrier diodes (SBDs) were fabricated on Ge-doped free-standing GaN substrates grown by hydride vapor phase epitaxy. Detailed material characterization was performed, and the results indicate the superiority of Ge doping in the GaN, which contributed to the SBDs with lower stress, fewer defects and higher quality. Based on the capacitance-voltage and currentevoltage measurements performed, SBDs achieved together with a low turn-on voltage Von (0.71e0.74 V), high current Ion/Ioff ratio (3.9 (cid:1) 107e2.9 (cid:1) 108), high Schottky barrier height (0.96e0.99 eV), and high breakdown voltage Vb (802 V for a 100 mm diameter). This shows that vertical GaN SBDs on the Ge-doped substrates are promising candidates for high power applications.
关键词： GaN device,Vertical SBDs,Low turn-on voltage,Ge-doped GaN substrates,High breakdown voltage
更新于2025-09-23 15:23:52
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Fabrication and up-conversion fluorescence property of Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped Ca-Si-Ti biomaterials
摘要： This work demonstrates bulk-type up-conversion biomaterials which could be used as a bone repair material with the ability to monitor bone mineralization. Er3+/Yb3+ co-doped Ca-Si-Ti (CST3: TiO2 content is 30 mol%) bulk biomaterials were prepared via containerless processing technique in an aerodynamic levitation furnace and with subsequently heat treatment. The up-conversion fluorescence property was influenced by Yb3+ doping concentration, heat-treatment and mineralization in simulated body fluid (SBF). Optimum emission intensities were obtained for the sample with 20 mol% of Yb3+ doping concentration and heat treatment at 937 °C for 2 h. Hydroxyapatite (HAP) deposition was observed on the surface of the samples after soaking in SBF for 14 days, and the up-conversion fluorescence intensity of the samples decreased with the increase of soaking time. This indicates that Er3+/Yb3+ co-doped CST3 materials are bioactive, in which the HAP mineralization in bone repair could be monitored by measuring the intensity change of up-conversion fluorescence.
关键词： Heat treatment,Up-conversion fluorescence,Containerless processing,Mineralization,Er3+/Yb3+ co-doped Ca-Si-Ti biomaterial
更新于2025-09-23 15:23:52
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-doped two-dimensional semiconductor quantum wells
摘要： We present a theoretical study of photoabsorption in n-doped two-dimensional (2D) and quasi-2D semiconductors that takes into account the interaction of the photocreated exciton with Fermi-sea (FS) electrons through (i) Pauli blocking, (ii) Coulomb screening, and (iii) excitation of FS electron-hole pairs—that we here restrict to one. The system we tackle is thus made of one exciton plus zero or one FS electron-hole pair. At low doping, the system ground state is predominantly made of a 'trion-hole'—a trion (two opposite-spin electrons plus a valence hole) weakly bound to a FS hole—with a small exciton component. As the trion is poorly coupled to photon, the intensity of the lowest absorption peak is weak; it increases with doping, thanks to the growing exciton component, due to a larger coupling between two-particle and four-particle states. Under a further doping increase, the trion-hole complex is less bound because of Pauli blocking by FS electrons, and its energy increases. The lower peak then becomes predominantly due to an exciton dressed by FS electron-hole pairs, that is, an exciton-polaron. As a result, the absorption spectra of n-doped semiconductor quantum wells show two prominent peaks, the nature of the lowest peak turning from trion-hole to exciton-polaron under a doping increase. Our work also nails down the physical mechanism behind the increase with doping of the energy separation between the trion-hole peak and the exciton-polaron peak, even before the anticrossing, as experimentally observed.
关键词： Fermi sea,trion-hole complex,exciton-polaron,photoabsorption,Pauli blocking,n-doped semiconductors,Coulomb screening
更新于2025-09-23 15:23:52
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Laser synthesis of iron nanoparticle for Fe doped hydroxyapatite coatings
摘要： Thin films of iron doped hydroxyapatite have been prepared by nanosecond Pulsed Laser Deposition (PLD). The composite target used for the deposition has been obtained by mixing commercial hydroxyapatite powder with iron-based nanoparticles produced by femtosecond laser ablation in liquid (LAL) (4% of iron nanoparticles). In fact, LAL technique allows to obtain metallic nanostructures without any toxic chemicals and reagents, with a green approach that is crucial for application in biological and medical technologies. Films have been prepared with substrate temperature growing from room temperature (RT) to 500 °C. The effect of deposition temperature on morphology, composition and structural properties of coatings has been investigated. Films deposited at higher temperature result dense and crystalline, they present microscale and nanoscale structures, an average surface roughness of 0.3 μm and magnetic properties suitable for biomedical applications.
关键词： PLD,Iron doped hydroxyapatite,Laser ablation in liquid,Regenerative orthopedic applications
更新于2025-09-23 15:23:52
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Influence of Cr doping on Schottky barrier height and visible light detection of ZnO thin films deposited by magnetron sputtering
摘要： A comparative study of the electrical and photodetection properties of ZnO and Cr doped ZnO thin films are being reported here. The films were deposited using magnetron sputtering. X-ray diffraction (XRD) revealed hexagonal crystal structure of the films with (002) preferred orientation. Pt/ZnO/Pt and Pt/Cr doped ZnO/Pt Schottky diodes were fabricated for photodetection studies. The Schottky barrier height was lowered for Cr doped ZnO film as compared to ZnO film. The ideality factor was improved upon Cr doping. Pt/ZnO/Pt diode was unresponsive to visible light, however, Pt/Cr doped ZnO/Pt diode showed response to visible light with short response and recovery times. The response of the Pt/Cr doped ZnO/Pt diodes to visible light is attributed to the reduction in band gap of the Cr doped ZnO thin film.
关键词： Thin films,Schottky contact,Chromium-doped Zinc oxide,Sputtering,Photodetectors
更新于2025-09-23 15:23:52
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Research on photo-radiation darkening performance of ytterbium-doped silica fibers for space applications
摘要： Yb3+/Al3+-doped and Yb3+/Al3+/P5+-doped silica fibers with almost identical Yb3+ doping concentrations were prepared using modified chemical vapor deposition methods. A harsh experimental environment for simultaneous photo-darkening (PD) and radio-darkening (RD) of an ytterbium-doped silica fiber (YDF) was established. The RD, PD, and photo–radio-darkening (PRD) of the YDF were characterized at two dose rates of 0.1 rad(Si)/s and 1 rad(Si)/s. The laser performances before and after the darkening process were tested under 974-nm pumping. The results demonstrated that the PD largely dominated the PRD kinetics of the YDF at a low dose rate (e.g., that in space) and that the PRD was not a superposition of RD and PD owing to the pump light bleaching if the induced loss was larger than the PD equilibrium level. The induced loss and defect types were investigated through absorption spectra and electron paramagnetic resonance. The results revealed that the P doping could enhance the PD, RD, and PRD resistances by inhibiting the formation of aluminum–oxygen hole centers.
关键词： photo-radio darkening,radio-darkening,photodarkening,defects in silica glass,ytterbium doped silica fiber
更新于2025-09-23 15:23:52
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Amine salts assisted controllable synthesis of the YVO4:Eu3+ nanocrystallines and their Luminescence properties
摘要： The Eu3+ doped YVO4 nanocrystallines with various morphologies were successfully synthesized by an amines (TETA, ETA and EDA) assisted hydrothermal process. By rationally adjusting the adding amount of TETA, ETA and EDA, the trepang-like, globular-like and pineapple-like Eu3+ doped YVO4 nanostructures can be conventionally obtained. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns indicate that these samples are all of the tetragonal structure. The SEM and TEM results show that the amines additives play an important role in morphology formation. Furthermore, the fluorescence properties of those samples are also systematically studied. Under the excitation of 280 nm, Eu3+ doped YVO4: nanostructures emit strong red fluorescence due to the transitions of 5D1-7F1 and 5D0-7FJ (J =1, 2, 3 and 4) of Eu3+ ions. The intensity of red fluorescence is related to not only the concentrations of Eu3+, but also the types of adding amines. The effective luminescence lifetimes of the trepang-like Y0.9Eu0.1VO4 nanocrystallines, the globular-lik and pineapple-like Y0.95Eu0.05VO4 nanocrystallines are 0.91 ms, 1.02 ms and 1.14 ms, respectively. It is believed that this study is beneficial to promote the development of color display industry.
关键词： hydrothermal,Amine salts,luminescence lifetimes,Eu3+ doped YVO4,fluorescence properties
更新于2025-09-23 15:23:52
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Research of Single-Event Burnout and Hardening of AlGaN/GaN-Based MISFET
摘要： This brief ?rst time presents single-event burnout (SEB) simulation results for conventional AlGaN/GaN gate ?eld plate MISFET (GFP-C MISFET), simultaneously, a hardened MISFET with electrode connected doped plugs in the buffer (EC-DP MISFET) is proposed for the ?rst time. The SEB triggering mechanisms contain the back-channel effect and following impact ionization dominated by electron in the high ?eld region. By comparing the simulation results from the GFP-C MISFET and proposed hardened EC-DP MISFET, the carriers induced by heavy ion can be quickly absorbed to drain and source electrode through EC-DP, so that the proposed EC-DP MISFET can achieve better SEB performance than conventional one. With a heavy ion having the linear energy transfer value of 0.6-pC/μm striking vertically, SEB threshold voltage obtained in GFP-C MISFET and hardened EC-DP MISFET is 280 and 338 V, respectively.
关键词： MISFET,single-event burnout (SEB) hardening,SEB,technology computer-aided design (TCAD),Electrode connected doped plugs (EC-DP)
更新于2025-09-23 15:23:52