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Optical, electrical, structural and magnetic properties of BiSe thin films produced by CBD on different substrates for optoelectronics applications
摘要： BiSe thin films have been grown on substrates as PMMA, ITO, glass and Si wafer by using chemical bath deposition (CBD) method. Deposition temperature and time and pH are kept to be constant during the production of the thin films. The thickness of BiSe thin films, which are produced on ITO, glass, PMMA and Si wafer substrate are 513, 468, 1039 and 260 nm, respectively. According to GAXRD results, the films, which are grown on glass and PMMA substrate, have amorphous structure, but, the films, which are grown on ITO and Si wafer substrate, have peaks of Bi2Se3 crystal. Grain sizes, crystallization number per unit area and dislocation density for ITO and Si wafer substrate are calculated as 112.40 nm and 43.04 nm; 2.25×10?5 and 7.91×10?5 (1/nm2), respectively. The contact angles and critical surface tension of distilled water, ethylene glycol, formamide and diiodamethane liquids for thin films grown on glass, ITO, PMMA and Si wafers were obtained by the Zisman method. The % transmittance and % reflectance values of thin films grown on glass, ITO, PMMA are calculated as % T: 79.90, 92.76 and 67.37; % R: 6.18, 2.07 and 10.59, respectively. Eg values of thin films grown on glass, ITO, PMMA are calculated as Eg=1.92; 2.18; 1.60 eV. The extinction coefficients, refractive indexes and relative dielectric constants of thin films grown on glass, ITO, PMMA are calculated as k=0.007; 0.002 and 0.012; n=1.65; 1.34 and 1.96; ε1=0.271; 0.083 and 0.528 respectively. Sheet resistance, hall mobility, sheet carrier densities, bulk carrier densities and conductivity types for glass, ITO, PMMA and Si are 6.52×107, 6.65×101, 1.09×108 and 6.45×102 (Ω/cm2); 2.38, 1.21×10?1, 5.34 and 1.52 (cm2/V.s); 4.01×1010, 7.71×1017, 1.06×1010 and 6.34×1015 (cm?2); 4.58×1014, 1.50×1022, 1.02×1014 and 2.89×1020 (cm?3); p, n, p and p, respectively. In addition, I–V characteristics and changes of magnetoresistance values versus magnetic field of the thin films are obtained by Van der Pauw method and HEMS.
关键词： magnetoresistance,thin film deposition,optical band gap,carrier density,surface properties,crystal growth
更新于2025-09-23 15:21:21
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Design and analysis of multi-hexagonal reversible encoder using photonic crystals
摘要： In this paper, a 4 × 2 reversible encoder with hexagonal lattice has been designed using two-dimensional photonic crystals with non-linear refractive index. In order to demonstrate the working of the encoder, we have used the multi-hexagonal shaped structure arranged in parallel with appropriate inclination to get the desired output. During its functionality as an encoder, more than 98% of the power is coupled at the output port to obtain logic 1 and less than 17.2% of the power is coupled for obtaining logic 0. In addition, during its functionality as a reversible encoder, the logic 1 and logic 0 correspond to 97.5% and 15.1%, respectively. The proposed encoder provides an improved contrast ratio of 12.18? dB and 11.5?dB for logical states of 01 and 10, respectively.
关键词： Photonic integrated circuits,Optical reversible encoder,Photonic crystal,Photonic band gap
更新于2025-09-23 15:21:21
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Investigation of photocatalytic, electrochemical, optical and magnetic behaviors of rare-earth double perovskites using combustion synthesized Gd2NiMnO6 nanostructures in the presence of different saccharides
摘要： This paper reports combustion synthesis of Gd2NiMnO6 nanostructures (GNMO NSs), for the ?rst time, through reaction between metal nitrates in the presence of different saccharides, as capping and reducing agents. Analysis of XRD, FT-IR, EDS, along with TEM and SEM images and also VSM and DRS spectra were applied to study the NSs. The VSM showed an antiferromagnetic behavior. The DRS spectroscopy ascertained semiconducting behavior of GNMO NSs with Eg ? 3.05 eV for optimum sample prepared in the presence of glucose at 1000 (cid:2)C. The CV was used to investigation of electrochemical property of the NSs. For the ?rst time, the photocatalytic behavior of the GNMO NSs was evaluated, using the degradation of organic dyes under UV irradiation. The photodegradation of EDT was almost similar to that of ES, except for initial times of the irradiation. The degradation percentage of EBT and ES in the presence of GNMO NSs was large, whereas that of MV was little in the time range.
关键词： Direct band gap,Photocatalysis,Antiferromagnetism,Gd2NiMnO6,Combustion,Nanostructures
更新于2025-09-23 15:21:21
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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
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[IEEE 2019 IEEE Conference on Antenna Measurements & Applications (CAMA) - Kuta, Bali, Indonesia (2019.10.23-2019.10.25)] 2019 IEEE Conference on Antenna Measurements & Applications (CAMA) - Development of a Wideband Substrate Integrated Waveguide Bandpass Filter Using H-Slotted DGS
摘要： In the current work, a new Wideband Substrate Integrated Waveguide Bandpass Filter (SIW-BPF) is presented. The target is to allow vertical roaming between the X and Ku band applications. As a first step, we performed a parametric study of different etched slot geometries namely, H-Slotted, T-Slotted, and U-Slotted DGS in order to examine the effects of altering different geometrical parameters of the unit on its response. H-Slotted DGS shows the highest FBW with 82.89% on the average compared to other geometries. As a second step, the cell size and the numbers of the H-Slotted DGS were optimized with the use of finite element method with the following constraints taken into consideration: low cost fabrication, high Q-Factor, compact size and easy integration. One of the designs was chosen for fabrication to validate the designed circuit. The measured results show that our optimized filter achieves an insertion loss of 2.01 dB at 8.5 GHz, a return loss higher than 11 dB and fractional bandwidth of 90.87% for a single cell and a fractional bandwidth of 80.05% for multiple cells. The measured results are in good agreement with the simulated results.
关键词： Substrate Integrated Waveguide (SIW),Finite Element Method,Ku-Band,Bandpass filter (BPF),Electromagnetic Band Gap structure (EBG),Wideband,X-Band
更新于2025-09-23 15:21:01
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Two stage modelling of solar photovoltaic cells based on Sb2S3 absorber with three distinct buffer combinations
摘要： Solar cell research has always been an attraction by virtue of its clean and green status. However, to overcome the implications of high cost and moderate efficiency, there has always been fierce competition to search alternative approach for designing efficient solar cells with optimal performance-cost ratio. Recently, antimony sulfide (Sb2S3) has received substantial attention as an absorber in thin film solar cells due to earth abundance, low cost, non-toxic property and high optical absorption. Still, its performance could not match Si based cells. In this work, we adopted two-stage simulation approach to design Sb2S3 absorber based heterojunction solar cell to enhance efficiency. Initial simulation for configuration optimization was done considering thickness, defect density, recombination (radiative, Auger) effect, carrier density of the Sb2S3 absorber layer. Buffer layer thickness and absorption coefficient optimization was taken up. Further, series and shunt resistance of the device as well as conduction band offset (CBO) at absorber/buffer interface was also optimized at initial stage only. In the next level of simulation, efficiency enhancement was achieved by optimizing optimal back contact metal work function, absorber layer band gap grading and temperature. The aforesaid two-stage optimization yielded efficiency ~24.81%, which is higher than conventional thin film solar cell. The optimal solar cell structure configuration, for Sb2S3 absorber solar cell, suggested a positive CBO of 0.26 eV (e.g.; ZnS buffer layer), a back contact metal work function of 5.1 eV (e.g.; Mo, Au) and band gap grading window ~1.31 to 1.62 eV.
关键词： Conduction band offset,Sb2S3 solar cell,Work function,Band gap grading,Simulation
更新于2025-09-23 15:21:01
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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
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Reconfigurable 2D/0D pa??n Graphene/HgTe Nanocrystal Heterostructure for Infrared Detection
摘要： Nanocrystals are promising building blocks for the development of low-cost infrared optoelectronics. Gating a nanocrystal film in a phototransistor geometry is commonly proposed as a strategy to tune the signal-to-noise ratio by carefully controlling the carrier density within the semiconductor. However, the performance improvement has so far been quite marginal. With metallic electrodes, the gate dependence of the photocurrent follows the gate-induced change of the dark current. Graphene presents key advantages: (i) infrared transparency that allows back-side illumination, (ii) vertical electric field transparency, and (iii) carrier selectivity under gate bias. Here, we investigate a configuration of 2D/0D infrared photodetectors taking advantage of a high capacitance ionic glass gate, large-scale graphene electrodes, and a HgTe nanocrystals layer of high carrier mobility. The introduction of graphene electrodes combined with ionic glass enables one to reconfigure selectively the HgTe nanocrystals and the graphene electrodes between electron-doped (n) and hole-doped (p) states. We unveil that this functionality enables the design a 2D/0D p?n junction that expands throughout the device, with a built-in electric field that assists charge dissociation. We demonstrate that, in this specific configuration, the signal-to-noise ratio for infrared photodetection can be enhanced by 2 orders of magnitude, and that photovoltaic operation can be achieved. The detectivity now reaches 109 Jones, whereas the device only absorbs 8% of the incident light. Additionally, the time response of the device is fast (<10 μs), which strongly contrasts with the slow response commonly observed for 2D/0D mixed-dimensional heterostructures, where larger photoconduction gains come at the cost of slower response.
关键词： gate-induced diode,infrared detection,narrow band gap nanocrystals,HgTe,graphene
更新于2025-09-23 15:21:01
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Predicted CsSi Compound: A Promising Material for Photovoltaic Applications
摘要： Exploration of photovoltaics materials has received enormous interest in a wide range of both fundamental and applied research. Therefore, in this work, we identify a CsSi compound with a Zintl phase for a promising candidate of photovoltaic materials by using global structure prediction method. Electronic structure calculations indicate that this phase possesses a quasi-direct band gap of 1.45 eV, suggesting that its optical properties could be superior to diamond-Si for capturing sunlight from the visible to the ultraviolet range. In addition, a novel silicon allotrope is obtained by removing Cs atoms from this CsSi compound. The superconducting critical temperature of this phase was estimated as a Tc of 9 K in terms of a substantial density of states at the Fermi level. Our findings represent a new promising CsSi material for photovoltaic applications, as well as a potential precursor of a superconducting silicon allotrope.
关键词： Zintl phase,quasi-direct band gap,photovoltaics,superconducting silicon allotrope,CsSi compound
更新于2025-09-23 15:21:01
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Cd12O12 cage cluster-assembled nanowires and band gap regulation: A first-principles investigation
摘要： Based on the first-principle calculation, the stability and electronic properties of Cd12O12 cluster-assembled nanowires and Na-doped Cd12O12 nanowire are studied. The results show that both Cd12O12 nanowire and Na-doped Cd12O12 nanowire are thermodynamically stable (at least at room temperature). The most stable Cd12O12 nanowire exhibits semiconducting properties with a direct energy gap. After doping Na atoms into the nanowire, the electronic properties of the Cd12O12-based nanowire present dramatic changes, and the system transforms from semiconducting to metallic. It can provide a theoretical guidance for the potential application of Cd12O12-based semiconductor devices.
关键词： Assembly,Band gap regulation,Na doped,Cd12O12 cage cluster,Cd12O12 nanowire
更新于2025-09-23 15:21:01