- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- parasitic patches
- Direct coupled
- gap coupled
- hybrid coupled
- composite mode
- Electronic Science and Technology
- SVKM’s DJSCE
- DIAT
-
Observation of Optical Band-Gap Narrowing and Enhanced Magnetic Moment in Co-Doped Sol–Gel-Derived Anatase TiO <sub/>2</sub> Nanocrystals
摘要： The magnetic behavior of TiO2 and doped TiO2 nanocrystals has been a challenge due to the unambiguous nature of defects present in oxide semiconductors. Here, a simple, low-temperature sol?gel method is developed for the synthesis of low-dimensional and highly efficient stable anatase TiO2 nanocrystals. The X-ray powder diffraction pattern and Raman spectra confirm the formation of a single-phase anatase structure of TiO2. High-resolution transmission electron microscopy studies reveal the crystalline nature of the sol?gel-derived nanocrystals. The increase in lattice parameters together with the shifting and broadening of the most intense Eg(1) mode in micro-Raman spectra of Co-doped TiO2 nanocrystals indicate the incorporation of Co in TiO2. Shifting of the absorption edge to the visible region in UV?visible spectra indicates narrowing of the band gap due to Co incorporation in TiO2. X-ray photoelectron spectra confirm the presence of Co2+ and Co3+ in Co-doped TiO2 samples. Oxygen vacancy defects lead to the formation of bound magnetic polarons which induces a weak ferromagnetic behavior in air-annealed 3% Co-doped TiO2 at room temperature. It is observed that irrespective of the dopant ion, whether magnetic or nonmagnetic, the overlapping of bound magnetic polarons alone can induce ferromagnetism, while the magnetic impurities give rise to an enhanced paramagnetic moment for higher Co concentrations. A detailed understanding on the variation of these magnetic properties by estimating the concentration of bound magnetic polarons is presented, which is in corroboration with the photoluminescence studies. The observed band-gap narrowing in Co-doped TiO2 nanostructures and the mechanism underlying the magnetic interactions associated with the magnetic impurity concentration are advantageous from an applied perspective, especially in the field of spintronic and magneto-optic devices.
关键词： spintronic,magnetic moment,nanocrystals,optical band-gap narrowing,TiO2,magneto-optic devices,Co-doped,sol?gel
更新于2025-09-23 15:21:21
-
Application of rubrene air-gap transistors as sensitive MEMS physical sensors
摘要： Micro electromechanical systems (MEMS) made of organic materials have attracted efforts on development a new generation of physical, chemical and biological sensors, for which the electromechanical sensitivity is the current major concern. Here, we present an organic MEMS made of a rubrene single crystal air-gap transistor. Applying mechanical pressure on the semiconductor results in high variations of drain current: an unparalleled Gauge factor above 4000 has been measured experimentally. Such a high sensitivity is induced by the modulation of charge injection at the interface between the gold electrode and the rubrene semiconductor as an unusual transducing effect. Applying these devices to the detection of acoustic pressure shows that force down to 230 nN can be measured with a resolution of 40 nN. This study demonstrates that MEMS based on rubrene air-gap transistors constitute a step forward to the development of high performance flexible sensors.
关键词： crystal,charge injection,organic MEMS,pressure sensor,air-gap transistor,OFET,rubrene
更新于2025-09-23 15:21:21
-
The effects of cathode electrodeposited polymer film on the long vacuum gap breakdown
摘要： Vacuum surface discharge is one of the most important issues for vacuum insulation. In this paper, a method for breakdown ?eld strength enhancement of long vacuum gap is put forward, through depositing polymer dielectric coating on the electrode surface. The physical mechanism that the polymer ?lm changes the electrode surface state is analyzed. After a layer of polymer ?lm is deposited on the electrode surface, the decreased surface ?eld strength and improved micro-surface state both help to suppress the ?eld electron emission from the cathode. The technique of cathode electrodeposition for high polymers such as epoxy resin (ER), epoxy acrylate (EA), polyimide (PI) and poly(ether-ether-ketone) (PEEK) was explored, and the thickness of the electrodeposited coating can reach 20–50 mm. The effects of the electrodeposited polymer coatings of electrodes on the 2.5 cm vacuum gap breakdown were studied under a high-voltage vacuum experiment platform. Experimental results showed that when ER, EA and PEEK coatings with thickness of 25–45 mm were respectively electrodeposited on the 95 cm2 plate cathode, the initial-breakdown ?eld strengths of the 2.5 cm vacuum gap were enhanced by 20.7%–22.4%. The enhancement of the initial-breakdown ?eld strength was restricted by the coating defects, grain boundary defects on the cathode surface, and the micro-triple-point emission after the fusing of some local coating points due to the electron bombardments.
关键词： vacuum gap breakdown,vacuum insulation,cathode electrodeposition,polymer dielectric coating,field electron emission
更新于2025-09-23 15:21:21
-
Electronic properties of graphene with point defects
摘要： This article attempts a point-by-point review of the electron spectrum of graphene containing defects (adsorbed atoms, substitutional atoms, vacancies) that can be adequately described within the Lifshitz model. In this regard, the known Hamiltonian for this model is calculated for the case of two-dimensional relativistic electrons, and the criteria for occurrence of an impurity resonance near a Dirac point are given. The theory of concentration band structure transformation of graphene is presented, from which it follows that a transport gap is opened upon reaching a strictly defined value of impurity concentration in the neighborhood of the energy of impurity resonance. At the same time, the question of the possibility (or impossibility) of localization in such a {spatially disordered system} of Dirac quasiparticles is analyzed. Based on this, it is possible to provide an explanation and present a description of a phenomenon recently observed in {impure graphene}, the metal-dielectric transition that appears as a direct consequence of the decrease of the Fermi energy of the system in the region of a transport gap. The concept of local spectrum rearrangement of graphene, which also occurs during the process of increased concentration of defects in it, is introduced and substantiated. Physical reasons are formulated, by which the position of the minimum of the low-temperature conductivity of graphene as a function of the Fermi energy of electrons corresponds to the impurity resonance energy rather than to the Dirac point, as has been validated in a number of theoretical and test studies. Here, it appears that the minimum value is not a universal magnitude, but depends on the concentration of defects. Analytical examination of impurity effects is accompanied by numerical modeling of the system under study, as a result of which complete correspondence has been established between these two approaches. In particular, the overall picture of spectrum rearrangement, localization of electron states, and also the effects having local nature are confirmed.
关键词： electron spectrum,transport gap,Lifshitz model,impurity resonance,metal-dielectric transition,graphene,local spectrum rearrangement,conductivity,point defects
更新于2025-09-23 15:21:21
-
[IEEE 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Zhenjiang, China (2019.8.4-2019.8.8)] 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Study on Anti-reflection Performance of Titanium Alloy Based on the Change of Repeat Times of Nanosecond Laser Processing
摘要： A new and accurate edge extension formula based on the Taguchi method is proposed to calculate the resonant frequency of electrically thin and thick rectangular patch antennas with an air gap (RPAAG) and rectangular patch antennas without an air gap. Based on 3205 antennas data random distribution in the electrical substrate thickness h/λd ranging from 0.001 to 0.2 and the dielectric constant ranging from 1.0 to 10.2, the edge extension formula is created with the Taguchi method. The resonant frequencies predicted using the proposed formula are in better agreement with simulated and measured results than those calculated with the existing formulas in other literatures, especially for electrically thick substrates. Furthermore, experimental results for the RPAAG are given, which shows that h/λd should be less than 0.13 in the design of a capacitively fed RPAAG.
关键词： Edge extension formula,resonant frequency,electrically thin and thick substrates,rectangular patch antenna with and without an air gap,Taguchi method
更新于2025-09-23 15:21:01
-
[IEEE 2019 IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems (COMCAS) - Tel-Aviv, Israel (2019.11.4-2019.11.6)] 2019 IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems (COMCAS) - Overview of High Frequency Electronics Integration Concepts for Gap waveguide based High Gain Slot Antenna Array
摘要： This paper presents an overview of different low-loss microstrip to waveguide transition designs suitable for integrating millimeter wave electronics to a gap waveguide based slot array. Typically, E-plane probe type of transitions are widely used at mmWave frequency range to couple RF signal from a TX/RX MMIC to the waveguide section. H-plane split-blocks are avoided due to leakage problem from tiny slits formed by imperfect metal connections. On the other hand, the traditional slot arrays are built using H-plane split blocks. This makes it very challenging to integrate electronics and other passive components such as diplexer filter directly to a high gain planar antenna array. To overcome this above mentioned problem, we propose to use low-loss H-plane transitions to integrate RF electronics with the multi-layer gap waveguide based slot array. We demonstrate a completely packaged front-end at E-band, showing the potential of the gap waveguide technology to build a very compact full-duplex wireless system.
关键词： E-plane transition,Slot arrays,Full-duplex,Integration and packaging,Gap waveguide
更新于2025-09-23 15:21:01
-
Profound optical analysis for novel amorphous Cu2FeSnS4 thin films as an absorber layer for thin film solar cells
摘要： In this study, quaternary kesterite Cu2FeSnS4 (CFTS4) has been selected due to its interesting optical and electrical characteristics. The CFTS4 films were prepared by exploiting the chemical bath deposition process at room temperature. The films were prepared at different deposition periods (1, 3, 5 and 7 h). The EDAX technique was helped in evaluating the compositional element ratio which near to 2:1:1:4. The morphology and structure of CFTS4 films have been examined by utilizing X-ray diffraction, and field emission scanning electron microscope techniques. XRD charts revealed the absence of sharp peaks and approved the amorphous nature of films under investigations. The transmittance and reflectance data were employed to compute the linear and nonlinear optical constants of the as-deposited CFTS4 films. The energy gap calculations for the CFTS4 films grown on glass substrate displayed a direct energy gap and by increasing the deposition time, a reduction in energy gap values from 1.41 to 1.19 eV was obtained. The deep analysis of linear/nonlinear optical properties as a function of deposition time has revealed many characteristics of the investigated films. Moreover, the nonlinear parameters (refractive index n2, nonlinear absorption coefficient βc and the third-order nonlinear optical susceptibility χ(3)) of the CFTS4 films were boosted with rising up the film thickness and their high values imply the possibility of utilizing these films in various optoelectronic applications.
关键词： Optical conductivity,Energy gap,Optoelectronic applications,Chemical bath deposition technique,CFTS4 thin films
更新于2025-09-23 15:21:01
-
Computational determination of structural, electronic, optical, thermoelectric and thermodynamic properties of hybrid perovskite CH3CH2NH3GeI3: An emerging material for photovoltaic cell
摘要： Owing to high power conversion efficiency and low-cost, methyl-ammonium lead-based halide (viz. CH3NH3PbI3) Perovskites have been emerging as the innovative candidate in the development of optoelectronic devices. However, the toxic lead in these materials is a major hurdle in its commercialization. Thus, there is an urgent need to replace lead with an appropriate element. Ethyl-ammonium based lead-free hybrid halide perovskites may be an alternative photovoltaic (PV) absorber material with appropriate band gap, high stability and non-toxic properties. Herein, we have investigated structural, electronic, optical, thermoelectric and thermodynamic properties of ethyl-ammonium germanium iodide (CH3CH2NH3GeI3 or EAGeI3) by full-potential augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code within the density functional theory (DFT). In this paper, we have found that EAGeI3 has direct band gap of 1.3 eV and high absorption coefficient greater than 104 cm-1 and indicating its suitability as PV absorber material. We have also calculated thermoelectric coefficients as a function of carrier concentration, chemical potential and temperature. The thermodynamic calculations have been done within the quasi-harmonic approximation. As EAGeI3 has been studied first time for PV applications, the present study may open a new vista for more exhaustive experimental and theoretical investigations in search of non-toxic and eco-friendly PV materials.
关键词： absorption coefficient,Seebeck Coefficient,Ethyl-ammonium based hybrid perovskite,figure of merit,band gap
更新于2025-09-23 15:21:01
-
Gap Plasmon of Virus-Templated Biohybrid Nanostructures Uplifting the Performance of Organic Optoelectronic Devices
摘要： Plasmonic nanostructures, which exhibit prominent localized surface plasmon resonance (LSPR) properties, are highly desirable for organic solar cells (OSC) and organic light-emitting diode (OLED) devices. In the present work, novel plasmonic bio-nanostructures are successfully synthesized via the self-densification of silver (Ag) and gold (Au) metallic nanoparticles (NPs) onto a genetically engineered M13 bacteriophage template. Owing to the unique charge selectivity of the peptide receptors on the M13 bacteriophage, the metallic NPs can be directly anchored onto the bacteriophage through charge-driven interactions without binder/surfactant. The resulting Ag/AuNP-M13 bio-nanostructures display extraordinary gap-plasmon effect as well as tremendously enhanced LSPR properties than the randomly dispersed Ag/Au NPs. The incorporation of Ag/AuNP-M13 bio-nanostructures tremendously improves the performance of both OSC and OLED devices. Specifically, a power conversion efficiency increment of 15.5% is recorded for the phage-modified OSCs; whereas an external quantum efficiency increment of 22.6% is achieved for the phage-modified OLEDs. Based on this environmentally benign virus-template approach, various plasmonic/photonic bio-nanostructures can be designed for diverse device applications.
关键词： field-enhancement,optoelectronics,M13 bacteriophage,metamaterials,self-assembly,gap-plasmon effect
更新于2025-09-23 15:21:01
-
Strongly coupled evenly divided disks: a new compact and tunable platform for plasmonic Fano resonances
摘要： Plasmonic artificial molecules are promising platforms for linear and nonlinear optical modulation at various regimes including the visible, infrared and terahertz bands. Fano resonances in plasmonic artificial structures are widely used for controlling spectral lineshapes and tailoring of near-field and far-field optical response. Generation of a strong Fano resonance usually relies on strong plasmon coupling in densely packed plasmonic structures. Challenges in reproducible fabrication using conventional lithography significantly hinders the exploration of novel plasmonic nanostructures for strong Fano resonance. In this work, we propose a new class of plasmonic molecules with symmetric structure for Fano resonances, named evenly divided disk, which shows a strong Fano resonance due to the interference between a subradiant anti-bonding mode and a superradiant bonding mode. We successfully fabricated evenly divided disk structures with high reproducibility and with sub-20-nm gaps, using our recently developed sketch and peel lithography technique. The experimental spectra agree well with the calculated response, indicating the robustness of the Fano resonance for the evenly divided disk geometry. Control experiments reveal that the strength of the Fano resonance gradually increases when increasing the number of split parts on the disk from 3 to 8 individual segments. The Fano-resonant plasmonic molecules that can also be reliably defined by our unique fabrication approach open up new avenues for application and provide insight into the design of artificial molecules for controlling light-matter interactions.
关键词： sketch and peel lithography,artificial molecules,Fano resonance,plasmon coupling,tiny gap
更新于2025-09-23 15:21:01