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根据BaF2晶体闪烁光快、慢成分波段的不同,设计并制备了用于抑制该晶体闪烁光慢成分的Al2O3/MgF2/Al/MgF2…光子带隙膜系。实验结果显示:加载光子带隙膜系的BaF2晶体,其闪烁光快/慢成分比提高80倍以上;经剂量为1×105 Gy的60Co γ射线辐照后,其透射光谱、发射光谱和发光衰减时间谱没有明显的变化,这表明由光子带隙膜系与BaF2晶体所构成的快闪烁器件不仅可有效避免慢成分的干扰,而且还具有很强的抗γ辐射性能。 相似文献
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光催化降解有机污染物由于其具有低能耗和绿色环保的特点,已经成为研究的热点. 氧化铋纳米晶体的带隙在2.0∽2.8 eV之间,利用它催化可见光降解有机污染物具有较高的活性,从而引起了越来越多的关注. 尽管近年来已经开发了几种制备Bi2O3基半导体材料的方法,但是仍然难以用简单的方法大规模地制备高活性的Bi2O3催化剂. 因此,开发简单可行的大规模制备Bi2O3纳米晶体的方法对于工业废水处理的潜在应用具有重要意义. 本文通过蚀刻商用BiSn粉末,然后进行热处理,成功地大规模制备了多孔Bi2O3. 获得的多孔Bi2O3在亚甲基蓝(MB)的光催化降解中表现出优异的活性和稳定性. 对该机理的进一步研究表明,多孔Bi2O3合适的能带结构允许生成活性氧物种,例如O2-·和·OH,可有效降解MB. 相似文献
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本文利用基于密度泛函理论(DFT)的第一性原理计算研究了它们的电子结构和光学性质.光学性质的计算结果和实验相一致.结果表明,Fe或Ag掺杂后,K2Ti6O13的带隙中出现了杂质带且其带隙值变小,因而使掺杂后的K2Ti6O13的吸收边发生红移并实现了其对可见光吸收.其中杂质带主要由Fe 3d态或Ag 4d态与Ti 3d态和O 2p态杂化而成.对于Fe掺杂的K2Ti6O13,杂质带位于带隙中间,因此可以作为电子从价带跃迁到导带的桥梁.对于Ag掺杂的K2Ti6O13,杂质带位于价带顶附近为受主能级,可以降低光生载流子的复合概率.实验和计算研究表明,通过Fe或Ag的掺杂可以实现了K2Ti6O13对可见光的吸收,这对进一步研究K2Ti6O13的光学性质具有重要意义. 相似文献
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以乙醇钽为前驱物,采用金属醇盐溶胶-凝胶技术,获得了Ta2O5湿凝胶,分析了不同条件下的溶胶-凝胶过程,并初步探讨了凝胶过程机理。Ta2O5的溶胶-凝胶过程主要受到水量、催化剂用量及钽源浓度等因素的影响:体系在强酸性条件下凝胶,且随着酸性的增强,体系凝胶时间明显缩短;当水量较少时,凝胶时间随水量的增加而增加,但当水量增加到一定程度时,体系凝胶时间基本不变;实验证明,通过增大溶剂用量,体系凝胶时间延长,气凝胶理论密度降低。通过对溶胶-凝胶过程的控制,结合超临界干燥技术,获得了密度低至44 mg/cm3的Ta2O5气凝胶样品。 相似文献
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采用射频磁控溅射和N2气氛退火处理制备了多晶Ga2O3薄膜和Cu掺杂Ga2O3薄膜.用X射线衍射仪、紫外-可见分光光度计、荧光光谱仪对Ga2O3薄膜和Cu掺杂Ga2O3薄膜的结构和光学性能进行了表征.结果表明,Cu掺杂后Ga2O3薄膜的结晶质量变差,透过率明显降低,吸收率增加,光学带隙减小.本征Ga2O3薄膜在紫外、蓝光和绿光出现了发光带,Cu掺杂后紫外和蓝光发射增强,且在475 nm 处出现了一个新的发光峰. 相似文献
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T. SrikumarM.G. Brik Ch. Srinivasa RaoN. Venkatramaiah Y. GandhiN. Veeraiah 《Physica B: Condensed Matter》2011,406(19):3592-3598
Li2O-ZrO2-SiO2: Ho3+ glasses mixed with three interesting d-block elemental oxides, viz., Nb2O5, Ta2O5 and La2O3, were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The luminescence spectra of Nb2O5 and Ta2O5 mixed Li2O-ZrO2-SiO2 glasses (free of Ho3+ ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Ta5+ and Nb5+ ions in the glass network. The Judd-Ofelt theory was successfully applied to characterize Ho3+ spectra of all the three glasses. From this theory various radiative properties, like transition probability A, branching ratio βr and the radiative lifetime τr, for 5S2 emission levels in the spectra of these glasses have been evaluated. The radiative lifetime for 5S2 level of Ho3+ ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied the La2O3 mixed glass exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Ho3+ ions. 相似文献
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A. Paskaleva M. ?apajna E. Dobro?kaK. Hušeková E. AtanassovaK. Fröhlich 《Applied Surface Science》2011,257(17):7876-7880
Hf-doped Ta2O5 thin films are studied with respect to their composition, dielectric and electrical properties. The incorporation of Hf is performed by sputtering of a 0.7 nm thick Hf layer on top of Ta2O5 and subsequent annealing to stimulate diffusion of Hf into Ta2O5 and their intermixing. The elemental in-depth distribution of the films is investigated by the time of flight secondary ion mass spectroscopy (ToF-SIMS), which has revealed that Hf and Ta2O5 are intermixed throughout the whole thickness. Two sub-layers exist in all the samples - an upper homogeneous Hf-doped Ta2O5 sub-layer and a near interfacial region which is a mixture of Ta- and Si-oxides. The X-ray reflectivity (XRR) analysis shows existence of interfacial layer with a thickness of about 1.9-2 nm, irrespectively of the total thickness of the stacks. Metal-oxide-Si structures with Ru and RuO2 metal electrodes have been prepared and investigated in terms of dielectric constant, effective work function (EWF) and interfacial layer parameters. The influence of post-metallization annealing steps on these parameters was also studied. 相似文献
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Effects of O2/Ar ratio and annealing temperature on electrical properties of Ta2O5 film prepared by magnetron sputtering 下载免费PDF全文
The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal phase when annealing temperatures are 800℃ or higher.The lattice constant of Ta2O5 decreases with the increase of the O2/Ar ratio,which indicates that oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies during the deposition process.For the films deposited in working gas mixtures with different O2/Ar ratios and subsequently annealed at 700℃,the effective dielectric constant is increased from 14.7 to 18.4 with the increase of the O2/Ar ratio from 0 to 1.Considering the presence of an SiO2 layer between the film and the silicon substrate,the optimal dielectric constant of Ta2O5 film was estimated to be 31.Oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies,and the oxygen vacancy density and leakage current of Ta2O5 film both decrease with the increase of the O2/Ar ratio.The leakage current decreases after annealing treatment and it is minimized at 700℃.However,when the annealing temperature is 800℃ or higher,it increases slightly,which results from the partially crystallized Ta2O5 layer containing defects such as grain boundaries and vacancies. 相似文献
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The Ti-doped Ta2O5 thin films (<10 nm) obtained by rf sputtering are studied with respect to their composition, dielectric and electrical properties. The incorporation of Ti is performed by two methods - a surface doping, where a thin Ti layer is deposited on the top of Ta2O5 and a bulk doping where the Ti layer is sandwiched between two layers of Ta2O5. The effect of the process parameters (the method and level of doping) on the elemental distribution in-depth of the films is investigated by the time of flight secondary ion mass spectroscopy (ToF-SIMS). The Ti and Ta2O5 are intermixed throughout the whole thickness but the layers are very inhomogeneous. Two sub-layers exist in all the samples — a near interfacial region which is a mixture of Ta-, Ti-, Si-oxides as well as TaSiO, and an upper Ti-doped Ta2O5 sub-layer. For both methods of doping, Ti tends to pile-up at the Si interface. The electrical characterisation is performed on capacitors with Al- and Ru-gate electrodes. The two types of MIS structures exhibit distinctly different electrical behavior: the Ru gate provides higher dielectric permittivity while the stacks with Al electrode are better in terms of leakage currents. The specific metal-dielectric reactions and metal-induced electrically active defects for each metal electrode/high-k dielectric stack define its particular electrical behavior. It is demonstrated that the Ti doping of Ta2O5 is a way of remarkable improvement of leakage characteristics (the current reduction with more than four orders of magnitude as compared with undoped Ta2O5) of Ru-gated capacitors which originates from Ti induced suppression of the oxygen vacancy related defects. 相似文献
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A phase transition has been discovered in Cd2Ta2O7 near 200 K which is about the same temperature at which Cd2Nb2O7 is known to become ferroelectric. However, Cd2Ta2O7 does not become ferroelectric below this transition. The nature of this transition was also studied in the Cd2Nb2?xTaxO7 series using low temperature X-ray, SHG, and DSC techniques. 相似文献
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Density functional theory (DFT) is performed on the structural and optical properties of undoped and N-doped Ta2O5. The optimized lattice constants of β-Ta2O5 are in good agreement with the experimental values. When O is replaced by N in Ta2O5, the substitutional doping of N in Ta2O5 clearly increases the refractive indices. The propagation of acoustic wave in two-dimensional (2D) photonic crystal of a honeycomb structure of air cylinder is investigated by the plane wave expansion method (PWEM). Our numerical results show that Ta2O5 has incomplete band gaps, indicating that only the TE mode appears. Ta2O4.5N0.5 is more suitable for background material. When a = 338 nm, r/a = 0.46, and Δ = 0.022 (ωa/2πc), a complete band gap appears in the red light range. 相似文献
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A detailed study of the effect of heavy-ion bombardment on Ta2O5 has been undertaken using a combination of radioactive tracer techniques, electron microscopy, and Rutherford backscattering. Crystalline Ta2O5 is amorphized at ~6 × 1013 ions cm?2, while at a dose of ~5 × 1016 ions cm?2 the electron microscopy reveals the development of random grains of a new crystalline phase. By ~1 × 1017 ions cm?2 the grains are not yet overlapping but still yield a diffraction pattern consistent with either δ-Ta-O (not to be confused with TaO) or Ta1?xO2, thus indicating that Ta2O5, like most other transition-metal oxides, is subject to preferential sputtering. Preferential sputtering was confirmed by backscattering analysis of specimens bombarded to high doses, where the average surface composition was found to be Ta1.8±0.2O2 or, equivalently, Ta2O2.2±0.2. The surface alteration had an average composition independent of the mass and energy of the incident ions. 相似文献
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Huihuan Guan Peide Han Yuping Li Hongwei Zhou Xue Zhang Ruizhen Zhang 《Optics Communications》2012,285(10-11):2656-2659
The current research work presents the theoretical results of demonstrating novel dichromatic filters, which consist of blue and yellow light. A one-dimensional photonic crystal or photonic heterostructure of Si/MgF2 is analyzed in detail by fully considering the effects of structural parameters using the transfer matrix method. The position and the number of defect modes are shown to have relationships with the repeat cycle counts of various photonic crystals. When the photonic heterostructures have the optimized structural parameters, defect modes can be obtained with high transmittances located in blue and yellow light. This photonic heterostructure is expected to be used in dichromatic filters with wide non-transmission range in a visible range. 相似文献
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本文研究了AgI(Cr2O3)复合离子导体的红外吸收光谱,近紫外、可见反射光谱。发现复合离子导体的两种谱图均与纯AgI,Cr2O3的不同。红外吸收光谱在882—889cm-1处有一新吸收峰。电子谱中,AgI从430nm开始向长波方向表现的光离解特性消失。本来Cr2O3由配位场效应而引起的d—d吸收跃迁以410nm,530nm为中心的反射谱带,现在410nm处的谱带消失。530nm处的谱带稍有红移,且随加入Cr2O3量的增多而强度减弱。代之以整个紫外、可见区的较强吸收。对此,结合透射电子显微镜的分析,用双声子耦合和介质的变形极化以及配位场理论对AgI(Cr2O3)复合离子导体的声子谱和电子谱进行了解析。
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