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Effect of 200?MeV Ag15+ ion beam irradiation at different fluences on WO3 thin films
摘要： The physical properties of thin films can be modified by swift heavy ion (SHI) beam irradiation of the target material. Spray-deposited tungsten trioxide (WO3) thin films of thickness 89 nm were irradiated with 200 MeV Ag15+ ion beam at various fluences of 5 × 1011, 1 × 1012, 5 × 1012 and 1 × 1013 ions/cm2. The X-ray diffraction pattern of the pristine film was orthorhombic, while the irradiated film became amorphous at different fluences except for 5 × 1012 ions/cm2; this may be due to the re-crystallization effect induced by irradiation. The observed Raman modes for the pristine film were in good agreement with those reported for the irradiated WO3 films. The intensity of Raman peaks decreased upto 5 × 1012 ions/cm2 and vanished completely at further higher fluences. The optical transparency of the pristine film was much higher than that of irradiated ones. Both the direct and indirect band gaps showed a red shift. AFM data revealed significant surface modifications after irradiation. Transport properties were also studied for both the pristine and irradiated films by the Hall effect. A decrease in resistivity was observed with the increase in fluence. These results are discussed in this paper.
关键词： WO3,Hall effect,Raman spectra,Indirect band gap,Irradiation
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - Kuala Lumpur (2018.8.15-2018.8.17)] 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - Bandgap Engineering of GaAsBi Alloy for Emission of up to 1.52 μm
摘要： Band gap engineering by incorporating bismuth into GaAs to form ternary GaAs1-xBix alloy was investigated. Series of GaAsBi samples with different Bi concentrations were grown by molecular beam epitaxy. Based on high resolution X-ray diffraction (HR-XRD) measurements, Bi concentration of up to 0.108 was successfully incorporated into the lattice. Sample with the highest Bi concentration, GaAs0.892Bi0.108, show room temperature photoluminescence (PL) emission with a peak wavelength of 1.52 μm and full-width-at-half-maximum (FWHM) of 89 meV. It was found that the incorporation of Bi into GaAs lattice affected both the conduction band as well as the valence band. The conduction band minimum reduces linearly by 23 meV/%Bi while the valence band maximum was best fitted by using the valence band anti-crossing (VBAC) model with coupling parameter, CBi of 1.65 eV.
关键词： band gap engineering,X-ray diffraction,molecular beam epitaxy,GaAsBi,photoluminescence
更新于2025-09-09 09:28:46
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Photo and thermally induced properties change in Bi/Ag/Se trilayer thin film
摘要： In this article, we have demonstrated the optical and structural properties change in Bi/Ag/Se trilayer thin films by the influence of thermal and photon energy. The trilayer films prepared by thermal evaporation technique were annealed and laser irradiated at room temperature. The X-ray diffraction study revealed the Ag2Se phase formation and the surface morphology change is being studied by Field emission scanning electron microscopy. The optical properties of the studied films were characterized by using FTIR spectrophotometer in the wavelength range 400–1200 nm. The reduction of optical band gap by both thermal and laser irradiation is being discussed on the basis of chemical disorderness, defect states and density of localized states in the mobility gap. The Raman shift due to annealing and irradiation supports the changes in the film. The large change in optical band gap in thermal annealing is useful for memory device and waveguide fabrication.
关键词： optical properties,annealing,band gap,laser irradiation,Trilayer thin films
更新于2025-09-09 09:28:46
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Gallium Oxide || Synthesis, optical characterization, and environmental applications of β-Ga2O3 nanowires
摘要： In this chapter, we present the synthesis, optical characterization, and environmental applications of the β-Ga2O3 nanowires. The gap-state and near-band-edge transitions of β-Ga2O3 nanowires were identified and studied. The defects states play an important role in their optical emission and photocatalytic property. Owing to its various interesting properties such as wide bandgap, chemical and thermal stability, robust defect states, large surface to volume ratios, β-Ga2O3 nanowires are very promising in potential applications in optoelectronic, environmental applications, and fundamental research in the future.
关键词： wide-band-gap semiconductors,synthesis,optical characterization,photocatalytic activity,β-Ga2O3 nanowires,environmental applications
更新于2025-09-09 09:28:46
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with pentagonal structure
摘要： Structure-property relationships have always been guiding principles for materials discovery. Here we explore the relationships to discover two-dimensional (2D) materials with the goal of identifying 2D magnetic semiconductors for spintronics applications. In particular, we report a density functional theory + U study of single-layer antiferromagnetic (AFM) semiconductor CoS2 with the pentagonal structure forming the so-called Cairo tessellation. We ?nd that this single-layer magnet exhibits an indirect band gap of 1.06 eV with electron and hole effective masses of 0.52 and 1.93 m0, respectively, which may lead to relatively high electron mobility. The hybrid density functional theory calculations correct the band gap to 2.24 eV. We also compute the magnetocrystalline anisotropy energy (MAE), showing that the easy axis of the AFM ordering is along the b axis with a sizable MAE of 153 μeV per Co ion. We further calculate the magnon frequencies at different spin-spiral vectors, based on which we estimate the N′eel temperatures to be 20.4 and 13.3 K using the mean ?eld and random phase approximations, respectively. We then apply biaxial strains to tune the band gap of single-layer pentagonal CoS2. We ?nd that the energy difference between the ferromagnetic and AFM structures strongly depends on the biaxial strain, but the ground state remains the AFM ordering. Although the low critical temperature prohibits the magnetic applications of single-layer pentagonal CoS2 at room temperature, the excellent electrical properties may ?nd single-layer semiconductor applications in optoelectronic nanodevices.
关键词： two-dimensional materials,magnon frequencies,N′eel temperature,biaxial strain,Cairo tessellation,antiferromagnetic semiconductor,density functional theory,band gap,magnetocrystalline anisotropy energy,pentagonal structure,spintronics
更新于2025-09-09 09:28:46
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Preparation and Photocatalytic Properties of ZnO Deposited TiO <sub/>2</sub> Nanotube Arrays by Anodization
摘要： ZnO doped TiO2 nanotube arrays (ZnO-TNTs) with an average diameter of 60～80 nm and an average length of 2～4 μm were prepared on the Ti substrate by a one-step anodizing method using NH4F/ethylene glycol as the electrolyte. The phase structure, morphology, chemical composition, photocatalytic property and mechanism of TNTs were studied by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectra, photoluminescence and photocatalytic degradation of methylene blue under visible light. The results showed that highly ordered ZnO doped TNTs were successfully prepared by anodization. ZnO nanoparticles were dispersively distributed inside the walls of TNTs. ZnO-TNTs having a different amount of ZnO was prepared by adjusting the concentration of Zn(NO3)2·6H2O in the electrolyte. It was found that by changing doping amount of ZnO, the width of the TiO2 band gap and the recombination rate of photo-generated electron–hole pairs also changed. The TNTs which doped with 1 mM ZnO showed the best degradation rate of methylene blue (MB). At the concentration of 1 cm2·mL?1 of ZnO-TNTs, the degradation rate reached at the level of 81.9% with 8 mg·L?1 methylene blue aqueous solution. Compared with undoped TNTs, the band gap of ZnO-TNTs reduced from 3.25 eV to 2.75 eV, and the recombination rate of photo-generated electron–hole pairs decreased significantly. The film of ZnO-TNTs prepared by the one-step anodizing method depicted excellent photocatalytic properties under visible light.
关键词： ZnO-TNTs,Anodization,Methylene Blue,Band Gap,Photocatalytic
更新于2025-09-09 09:28:46
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How To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis Spectra
摘要： A misuse of the Tauc plot to determine the band gap energy of semiconductors may lead to erroneous estimates. Particularly large errors can be associated with characterization of modified semiconductors showing a significant absorption of sub-band gap energy photons. Taking the model methyl orange/titanium dioxide system, we address the problem and discuss how to apply the Tauc method correctly.
关键词： band gap energy,UV?Vis spectra,Tauc plot,methyl orange,modified semiconductors,titanium dioxide
更新于2025-09-09 09:28:46
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Synthesis and characterization of Mn doped ZnS pellets
摘要： Semiconducting nano-phosphor pellets have been fabricated by hydraulic pressure, using ZnS and Mn doped ZnS semiconducting materials, which is synthesized by physical evaporation technique. Structural characterizations of synthesized semiconducting nanophosphor materials and pellets have been done by X-ray diffraction measurement and SEM while optical characterizations are done by UV-Visible absorption measurement. XRD pattern showed that the synthesized ZnS, Mn doped ZnS materials and pellet have cubic structure with preferential orientation along (111) planes. Optical absorption measurements indicated that the absorption decreases with increase of percent of Mn in pellet. The average maximum grain size (25.13 nm), Minimum dislocation density (1.57 × 1011/cm3), lattice constant (5.398?) and minimum band gap (3.2 eV) have been obtained. Suitable explanation is given in this paper.
关键词： Band Gap,Grain Size,MN,Lattice Constant,ZNS
更新于2025-09-09 09:28:46
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Structural, morphological, optical and dielectric properties of M <sup>3+</sup> /PVA/PEG SPE Films (M = La, Y, Fe or Ir)
摘要： Low band gap polymer complexes are promising due to its flexibility, and exhibiting electronic and optical properties of inorganic semiconductors. The effect of PEG on the physical properties of PVA was evaluated. Then, blend (PVA: PEG = 50:50) doped with rare earth (La or Y) and transition metal (Fe or Ir) chlorides to obtain solid polymer electrolyte films. XRD shows that adding PEG to PVA results in a new peak, 2θ = 23o with increased intensity as PEG ratio increases. However, doping with La3+, Fe3+ or Ir3+ eliminate this peak and decrease the crystallinity. SEM exhibits significant changes in the morphology of films. FTIR confirms miscibility between PVA & PEG and the complexation of the salts. The optical band gap (Eg) of PVA ~ 5.37 eV, decreased slightly by blending with PEG. While it decreased significantly to 2.64 eV and 2.78 eV after doping with Fe3+ or Ir3+. There are a consistency between Eg values obtained by Tauc's model and that obtained from the optical dielectric loss. The dielectric constant and loss, in temperature range 303–405 K & frequency range 1.0 kHz ‐ 5.0 MHz, indicate one or two relaxation peak(s) depending on the film composition. Accordingly, conduction mechanism varied between correlated barrier hopping and large polaron tunneling. The DC conductivity was strongly depend on the dielectric loss. The transition metal salts appear to be more effective than the rare earth ones in increasing σac of films to higher values that candidates them in semiconductors industry.
关键词： conduction mechanism,low band gap polymers,activation energy,PVA/PEG blend,rare earth metal complexation,solid polymer electrolyte
更新于2025-09-09 09:28:46
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Precise determination of electron-affinity and band gap via optical response and optical spectra
摘要： In order to obtain both the band gap and a?nity of semiconductor by photoelectric e?ect and optical spectra, Lee A. DuBridge`s formula which describes the mathematical relationship between photocurrent and photon energy in metal is extended in semiconductor. Thus cut-o? energy of photon can be ?gured out via this formula, at the same time, the a?nity of semiconductor can be determined from the di?erence between cut-o? energy and band gap detected by optical spectra in semiconductor. The results of application on ?ve semiconductors prove that the method proposed in this paper is credible, the good agreements between experimental light energy-photoelectric yield curves and theoretical curves demonstrate that the classic Lee A. DuBridge`s theory of surface photoemission does an excellent job of ?tting the photo absorption pro?le shapes of semiconductor as an earlier application on metals, these results suggest that the Lee A. DuBridge`s formalism, which is straightforward and physical, may be of signi?cant utility in semiconductor spectroscopy. It is hoped also that the results will encourage a comprehensive theoretical analysis of the applicability of semiconductor. Beside, how the band gap of Cr3+ doped n-type TiO2 is controlled by composition of Ti is express with mathematical way.
关键词： Semiconductor,Determination,Band gap,Cut-o? energy,A?nity
更新于2025-09-09 09:28:46