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Effect of gamma irradiation dose on the structure and pH sensitivity of ITO thin films in extended gate field effect transistor
摘要： Even though several studies have demonstrated the use of Indium Tin Oxides (ITO) as an extended gate field effect transistor (EGFET), the effect of different doses of gamma radiation on the intrinsic properties of the ITO films has not been considered. This study investigates the effect of gamma irradiation on the structural, optical, morphological and electrical properties as well as pH sensitivity (as an extended gate field effect transistor) of ITO thin films. ITO thin films with thickness of 400 nm were prepared using a radio frequency sputtering technique. The samples were then subjected to various doses of gamma radiation from a Co-60 radio-isotope (0.5 kGy, 1 kGy, 1.5 kGy, and 2 kGy). The structural and morphological changes as well as transmission and absorption of the thin films were analyzed using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field-Emission Scanning Electron Microscope (FESEM) and UV-Vis spectrophotometry, before and after irradiation. The irradiated ITO thin films were then used as an extended gate field effect transistor to determine its ability to improve sensitivity as pH sensors. The grain size and transmittance in the range 300-900 nm of the ITO films were found to decrease with increasing gamma irradiation dose. In contrast, the uniformity and surface roughness of ITO thin films increased with increasing gamma radiation dose due to the formation of lattice defects. Moreover, the electrical resistance of the thin films increased with increasing dose because of the low current density and high number of surface defects associated with irradiation. The pH sensitivity of the ITO thin films improved after irradiation, possibly due to the concomitant increase in surface roughness with increasing radiation dose. The improvements in the pH sensitivity of ITO thin films after irradiation justify their potential use as pH sensors.
关键词： EGFET,pH sensor,Optical band gap,Gamma irradiation,X-ray diffraction,Indium Tin Oxide,Thin films
更新于2025-09-10 09:29:36
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Physical properties of Cd-doped ZnS thin films
摘要： In this research, un- and Cd-doped ZnS nanostructures were synthesized using an electrodeposition method. The electrolyte contained 20 mM ZnCl2, 20 mM Na2S2O3 and the various amounts of CdCl2 solution. The X-ray diffraction (XRD) patterns of the as-deposited samples exhibited that Cd doping lead to decrease the crystallite size (D) of ZnS meanwhile the lattice strain, lattice stress, dislocation density (γ), and stacking fault energy (SF) were increased. Field emission scanning electron microscopy (FESEM) images depicted very fine equiaxed grains (20 to 50 nm), in addition to big grains (200 to 400 nm) with the preferential orientation. The reflectance spectra of ZnS thin films indicated a decrease in the reflectance peaks and refractive index (n), after Cd doping. Based on the transmission spectra, the un- and Cd-doped ZnS samples showed an absorption edge between 328 – 357 nm. The band gap energy for undoped ZnS sample was estimated as 3.95 eV, which it was reduced to 3.63 eV for the Cd-doped ZnS samples owing to the presence of imperfections and crystalline disorder in the Cd-doped samples. Furthermore, the obtained dielectric constant of the Cd-doped ZnS thin films was smaller than undoped ZnS sample, which means that the Cd-doped ZnS samples were more appropriate than the undoped ZnS sample for application in the fast photodetectors. The photoluminescence (PL) spectra of the undoped ZnS thin film was presented six emission peaks at 340, 413, 536, 574, 748, and 878 nm as an outcome of near band emission (NBE) and crystalline defects such as zinc interstitials (IZn), zinc vacancies (VZn), sulfur interstitials (IS), ZnS self-defect, and the defect states between the valence band (VB) and the conduction band (CB) of ZnS. Moreover, the PL emission of the Cd-doped ZnS samples demonstrated a red-shift relative to the undoped sample, which verified the UV-vis spectroscopy results.
关键词： nanostructures,electrodeposition,wide band gap,dielectric constant,Cd-doped ZnS
更新于2025-09-10 09:29:36
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MoS <sub/>2</sub> Nanoflowers as a Gateway for Solar-Driven CO <sub/>2</sub> Photoreduction
摘要： The layering of transition metal dichalcogenides (TMD) has revealed unprecedented engineering opportunities for optoelectronics, field emitter and photocatalysis applications. Precise and controlled intrinsic material property combinations is the crucial demand needed for visible light photocatalysis optimization, which we demonstrate in this work with MoS2 nanoflowers containing abundant edge plane flakes for CO2 photoreduction optimization. This is the first time controlled imperfections and flake thickness through facile CVD synthesis was demonstrated on the nanoflowers, revealing the tuning ability of flake edge morphology, nanoflower size, stacked-sheet thickness, optical band gap energy (Eg) and catalytic function. These influences facilitated Eg tuning from 1.38 to 1.83 eV and the manifestation of the 3R phase prompting improvement to the catalytic behavior. The ‘sweet spot’ of higher catalytic activity during photoreduction experiments was found in those with plentiful nanoflower density and thick edge-site abundance. Ample edge-sites with dangling bonds, and crystal impurities assisted in lowering the Eg to achieve reduced recombination for improved photocatalytic reactions, including those found on what would have been a typical chemically inert basal plane. The production rates of CO improved two-fold after a calculated post-treatment reduction step. This reliable CVD technique for nanoflower synthesis paves the way for enhanced understating of synthetic parameters for defect-laden 2D TMD nanoflower structures. We also note that photocatalysis should consider Mars applications, as deep space humans exploration will be require harvesting of the CO2 rich atmosphere to generate fuel from sustainable resources, such as the sun.
关键词： molybdenum disulfide,band gap tuning,visible light catalyst,transition metal dichalcogenide
更新于2025-09-10 09:29:36
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Band Gap Optimization Design of Photonic Crystals Material
摘要： The photonic crystal has a fundamental characteristic - photonic band gap, which can prevent light to spread in the crystals. This paper studies the width variation of band gaps of two-dimension square lattice photonic crystals by changing the geometrical shape of the unit cells' inner medium column. Using the finite element method, we conduct numerical experiments on MATLAB 2012a and COMSOL 3.5. By shortening the radius in vertical axis and rotating the medium column, we design a new unit cell, with a 0.3*3.85e-7 vertical radius and a 15 degree deviation to the horizontal axis. The new cell has a gap 1.51 percent wider than the circle medium structure in TE gap and creates a 0.0124 wide TM gap. Besides, the experiment shows the first TM gap is partially overlapped by the second TE gap in gap pictures. This is helpful to format the absolute photonic band gaps and provides favorable theoretical basis for designing photonic communication material.
关键词： band gap,photonic crystals,finite element method,MATLAB,COMSOL
更新于2025-09-10 09:29:36
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Influence of thermal annealing on structural and optical properties of RF-sputtered LiTaO <sub/>3</sub> thin films
摘要： Near stoichiometric ratio lithium tantalate (LiTaO3) thin film possesses unique performance advantages compared with bulk LiTaO3 single crystal in applying in thermal sensors and detectors. Here, LiTaO3 thin film is prepared on Pt/Ti/SiO2/Si(100) substrate by the method of RF magnetron sputtering. The authors conduct research on the structure and optical properties of LiTaO3 thin film under the conditions of annealing temperatures varying from 550 °C to 700 °C. Besides, the authors also study on optical constants of the LiTaO3 thin film which includes refractive indices, extinction coefficients and optical band gap energy by spectroscopic ellipsometry. The results show that optical band gap energy Eg will increase along with the grain size’s increase. Moreover, the results demonstrate that the best annealing temperature is 600 °C. Under the best annealing condition, the obtained refractive index, extinction coefficient k and optical band gap energy Eg is 2.05, 2×10?5 and 3.82 eV, respectively. These values are consistent with that of lithium tantalate single crystal. All results above mentioned proving that lithium tantalate (LiTaO3) thin film prepared by RF magnetron sputtering possesses a good crystallinity and ordered structure.
关键词： optical constants,lithium tantalate thin film,RF magnetron sputtering,optical band gap Eg
更新于2025-09-10 09:29:36
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Optical properties and electronic structures of Cu <sub/>2</sub> ZnSnS <sub/>4</sub> , Cu <sub/>2</sub> ZnGeS <sub/>4</sub> , and Cu <sub/>2</sub> Zn(Ge,Sn)S <sub/>4</sub> and Cu <sub/>2</sub> Zn(Ge,Sn)Se <sub/>4</sub> solid solutions
摘要： Cu2Zn(GexSn1%x)S4 (CZGTS) samples were synthesized by a mechanochemical process and sequential heating. The phases in the obtained powders were analyzed by X-ray di?raction. The band-gap energies of the CZGTS samples were determined by the di?use re?ectance spectra of UV–vis–NIR spectroscopy. The band gap energy of the CZGTS system linearly increased from 1.49 eV for Cu2ZnSnS4 (x = 0.0) to 2.25 eV for Cu2ZnGeS4 (x = 1.0). Their energy levels of valence band maximum (VBM) from the vacuum level were estimated from the ionization energies measured by photoemission yield spectroscopy (PYS). The energy levels of conduction band minimum (CBM) were determined by addition of the band-gap energies to the VBM levels. The energy level of VBM of the CZGTS solid solution was almost constant. On the other hand, the CBM level of the CZGTS solid solution linearly increased from %3.96 eV for Cu2ZnSnS4 (x = 0.0) to %3.28 eV for Cu2ZnGeS4 (x = 1.0) with the increasing Ge content. For CZGTS solar cells with CdS bu?er layer, unfavorable cli?-type conduction band o?set was expected. We also synthesized Cu2ZnSnSe4, Cu2ZnGeSe4, and Cu2Zn(Ge,Sn)Se4 (CZGTSe) solid solution samples and determined their energy levels of VBM and CBM. For Cu2Zn(GexSn1%x)Se4 system with 0.3 3 x 3 1.0, similar cli?-type conduction band o?set was is expected. However, desirable positive spike-type conduction band o?set was expected for the Cu2Zn(GexSn1%x)Se4 solar cells with 0.0 3 x 3 0.2 and CdS bu?er layer.
关键词： photoemission yield spectroscopy,Cu2Zn(GexSn1%x)S4,conduction band minimum,valence band maximum,band-gap energies,solar cells
更新于2025-09-09 09:28:46
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Effects of polyvinylpyrrolidone on structural and optical properties of willemite semiconductor nanoparticles by polymer thermal treatment method
摘要： Willemite is an inorganic semiconductor material used for optoelectronic applications. The present study purposes a new polymer thermal treatment method involving calcination temperature to fabricate the willemite nanoparticles. The effects of polyvinylpyrrolidone (PVP) on the structural and optical properties of the material were thoroughly investigated. Thermogravimetric and its derivative confirmed the decomposition behavior of PVP. The minimum calcination temperature to decompose PVP was appraised at 740 °C. The FTIR and the Raman analyses confirmed the presence of organic source before the calcination process and the formation of the crystalline structure of the willemite nanoparticles after the heat treatment. The optimum PVP concentration in this study based on the FTIR results was found to be 40 g L-1. This is the minimum concentration at which the willemite nanoparticles remained pure with homogenous distribution. X-ray diffraction analysis of the PVP samples before calcination was confirmed to be amorphous, and upon calcination between 800 and 1000 °C, an a-willemite phase was obtained. The morphology and the average particle size were determined with FESEM and HR-TEM analysis. The average particle size is between 23.8 and 36.7 nm. The optical energy band was found to be increasing from 5.24 to 5.32 eV with the corresponding increase in PVP concentration from 20 to 50 g L-1. The findings in this study provides a new pathway to understand the effects of PVP concentrations on the structural and optical properties of willemite semiconductor nanoparticles as it may have key potential applications for future optoelectronic devices.
关键词： Willemite,Nanoparticles,Band gap,Calcination,Polyvinylpyrrolidone,Semiconductors
更新于2025-09-09 09:28:46
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Reference Module in Materials Science and Materials Engineering || Nano-Structured Diluted Magnetic Semiconductors
摘要： Diluted magnetic semiconductors (DMS) materials have attracted much interest in recent years because of the combination of both semiconducting and magnetic properties within the same material. Among the potential applications that DMS materials can offer is spintronics which exploits both the electron charge associated with the intrinsic spin of the electron. DMS are semiconductors doped with magnetic impurities. Physical properties, like band gap energy or magnetism, are now not only a function of the particle size but also of the doping level. Therefore, ordered arrays of nanometer sized magnetic semiconductors are promising components for new devices in magneto- or spin electronics.
关键词： Diluted magnetic semiconductors,Band gap energy,Spintronics,Nanometer sized magnetic semiconductors,Magnetic impurities
更新于2025-09-09 09:28:46
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Degradation of GaN-on-GaN vertical diodes submitted to high current stress
摘要： GaN-on-GaN vertical devices are expected to ?nd wide application in power electronics, thanks to the high current densities, the low on-resistance and the high breakdown voltage. So far, only few papers on the reliability of GaN-on-GaN vertical devices have been published in the literature. This paper investigates the degradation of GaN-on-GaN pn diodes submitted to stress at high current density. The study was carried out by means of electrical characterization and electroluminescence (EL) measurements. We demonstrate that: (i) when submitted to stress at high current density, the devices show signi?cant changes in the electrical characteristics: an increase in on-resistance/turn-on voltage, an increase in the generation/recombination components, the creation of shunt-paths. (ii) the increase in on-resistance is strongly correlated to the decrease in the EL signal emitted by the diodes. (iii) the degradation kinetics have a square-root dependence on time, indicative of a di?usion process. The results are interpreted by considering that stress induces a di?usion of hydrogen from the highly-p-type doped surface towards the pn junction. This results in a decrease in hole concentration, due to the creation of MgeH bonds, and in a lower hole injection. As a consequence, on-resistance increases while EL signal shows a correlated decrease.
关键词： Wide band gap semiconductors,Bulk GaN substrates,Vertical diodes,pn junction,Di?usion,Gallium nitride,Hydrogen,Degradation
更新于2025-09-09 09:28:46
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Optical and Morphological properties of environmentally benign Cu-Tin Sulphide Thin films grown by Physical Vapor Deposition Technique
摘要： Present work has set about the synthesis of Tin-Diethyl dithiocarbamate Sn (S2CN (Et) 2) n]) and Copper diethyldithiocarbamate Cu (S2CN(Et)2) complex by utilizing single source method. Sn (S2CN (Et) 2) n]) complex are further used for deposition of Tin Sulphide thin films via Physical Vapor deposition with varying concentration of copper acting as dopant specie. The fabricated doped and un-doped films were confronted to functional group detection (FTIR), optical (Uv-Vis), structural (XRD) and morphological (SEM, EDX) analysis to retrieve the hidden information. FTIR peaks of Copper and Tin complex confirmed the formation of dithiocarbamate complexes by enumerating the stretching and bending vibrational modes of bonding and metal Sulphur linkage. X-ray diffraction elucidate the predominant phase of SnS with 1:1 ratio which depicted the fabrication at high temperature. Optical investigation represented the decrease in band gap by 6% extrinsic addition while increase at 10 % doping. The enhancement in band gap is also clear from the increased absorption edge upon 10% addition. Surface morphology of films was heterogeneous along flakes with compaction of spherical particles as demonstrated by SEM. The obtained results of material (SnS) being environmentally benign were therefore discussed to assess its aptness in optoelectronic devices.
关键词： Physical vapor deposition,band gap,doping,Tin Sulphide,FTIR
更新于2025-09-09 09:28:46