共查询到19条相似文献,搜索用时 78 毫秒
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通过热蒸发方法成功制备出SdS0.65Se0.35纳米带,得到的纳米带表面光滑,宽度厚度均一,表现出很高的结晶质量.使用近场光学显微镜对纳米带室温下的带边荧光波导和光致荧光近场光谱进行研究.发现SdS0.65Se0.35纳米带呈现良好的光波导的特性;同时通过近场光学显微镜得到的空间分辨光谱,发现随着传播距离的增大,纳米带的光致荧光光谱有持续的红移现象.这种光谱红移现象是带间跃迁过程中带尾态的吸收效应引起的,并作了光谱带尾态吸收的理论模拟与实验结果进行比较.光波导传输过程中光谱的变化反映了信息在整个传导过程中的情况,体现了信息传递过程中的稳定性和有效性.三元合金材料SdS0.65Se0.35纳米带的波导和光谱性质研究,对于其他组分可调的三元合金纳米结构的制备和研究,及发展新型的纳米功能器件有重要意义. 相似文献
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用密度泛函理论和非谐振子模型计算了晶体HgGa2S4和Hg0.5Cd0.5Ga2S4的能带结构、态密度、化学成键及线性、非线性光学性质。结果表明:HgGa2S4的价带顶部主要是Ga-S成键态的贡献,导带底部主要是Ga-S反键态的贡献; Hg0.5Cd0.5Ga2S4的价带顶部主要由S-3p轨道组成,导带底部主要是Ga-S反键态的贡献。布居分析表明Ga-S键主要是共价成分,而Hg-S和Cd-S键主要是离子成分。HgGa2S4的折射率计算值与实验值在低能量区很好吻合。另外,HgGa2S4的能隙计算值比Hg0.5Cd0.5Ga2S4小,而二阶非线性极化率比Hg0.5Cd0.5Ga2S4大。 相似文献
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采用传统固相法和水热法成功地制备出棒状La2Zr2O7:Eu3+荧光粉. 利用X射线粉末衍射仪、透射电镜和荧光光谱仪等分析了产物的结构、形貌和发光特性. 结果表明红色荧光粉La2Zr2O7:Eu3+有良好的晶相,属于立方结构,空间点群为Fd3m; 其形貌主要为纳米棒, 平均直径约47 nm, 长度为50~700 nm. 并对纳米棒的生长机理进行了探讨. 在466 nm蓝光激发下,La2Zr2O7:Eu3+荧光粉能发射出Eu3+的特征红色荧光,发射主峰位于616 nm处,归属于Eu3+的5DO→7F2超灵敏电偶极跃迁.此外,在产物的发射光谱中能够观察到5D1→7FJ (J=0, 1, 2)跃迁和5D1→7FJ (J=1, 2, 4)跃迁的劈裂峰,这说明Eu3+处在低对称性的晶体场格位中. 相似文献
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采用化学自燃烧法制备了不同Ag+掺杂浓度的Y2O3:Eu纳米晶体粉末样品([Y3+]∶[Eu3+]∶[Ag+]=99∶1∶X,X=0—3.5×10-2),以及通过退火处理得到了相应的体材料.根据X射线衍射谱确定所得纳米和体材料样品均为纯立方相.实验表明在纳米尺寸样品中随着Ag离子浓度的增加,荧光发射强度随之增加,当X=2×10-2时达到最大值,其发光强度比X=0时提高了近50%.当Ag离子浓度继续增加,样品发光强度保持不变.在相应的体材料样品中则没有观察到此现象.通过对各样品的发射光谱,激发光谱,X射线衍射图谱,透射电镜(TEM)照片和荧光衰减曲线的研究,分析了引起纳米样品荧光强度变化的原因是由于Ag离子与表面悬键氧结合,从而使这一无辐射通道阻断,使发光中心Eu3+的量子效率提高;Ag+的引入所带来的另一个效应是使激发更为有效.这两方面原因使发光效率得到了提高. 相似文献
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β-Ga2O3是一种宽带隙半导体材料,能带宽度Eg≈5.0eV,在光学和光电子学领域有广泛的应用。用射频磁控溅射方法在Si衬底和远紫外光学石英玻璃衬底制备了本征β-Ga2O3薄膜及Zn掺杂β-Ga2O3薄膜,用紫外 可见分光光度计、X射线衍射仪、荧光分光光度计对本征β-Ga2O3薄膜及Zn掺杂β-Ga2O3薄膜的光学透过、光学吸收、结构和光致发光进行了测量,研究了Zn掺杂和热退火对薄膜结构和光学性质的影响。退火后的β-Ga2O3薄膜为多晶结构,与本征β-Ga2O3薄膜相比,Zn掺杂β-Ga2O3薄膜的β-Ga2O3(111)衍射峰强度变小,结晶性变差,衍射峰位从35.69°减小至35.66°。退火后的Zn掺杂β-Ga2O3薄膜的光学带隙变窄,光学透过降低,光学吸收增强,出现了近边吸收,薄膜的紫外、蓝光及绿光发射增强。表明退火后Zn掺杂β-Ga2O3薄膜中的Zn原子被激活充当受主。 相似文献
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本文以流变相反应法原位合成了聚对苯撑/LiNi0.5Fe2O4纳米复合热电材料,并对其热电性能进行表征,研究了放电等离子烧结时保温时间对其热电性能的影响.结果发现,复合材料铁氧体颗粒粒径为100---300nm,其外部被一层聚对苯撑膜包覆.电子在Fe2+和Fe3+之间的跳跃机理在铁氧体电导中占主导作用,因此聚对苯撑/LiNi0.5Fe2O4复合材料具有n型导电特性.随着保温时间增加,复合材料电导率基本不变,但热导率逐渐增大且Seebeck系数逐渐减小,导致热电优值系数降低.由于结合了有机物高电导率和低热导率以及无机材料高赛贝克系数的优点,所制备的复合材料热电性能较单一材料有较大提高. 相似文献
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为研究Yb3+离子浓度变化对Tm3+离子在蓝色波段荧光强度的影响,以NaF和La(NO3)3为原料,采用水热法制备了Tm3+和Yb3+共掺的Tm3+/ Yb3+∶LaF3纳米颗粒.用X射线衍射对LaF3纳米颗粒进行表征的结果显示,纳米晶体结构呈六方相.透射电镜的观测结果显示,纳米颗粒样品大小均匀、分散性良好.在波长为800 nm的激光激发下,观测到了上转换蓝光发射,其中包括波长为474 nm和479 nm的较强的荧光辐射(相应的跃迁为1G4→3H6)和波长位于450 nm的强度较弱的荧光发射(相应的跃迁为1D2→3F4).通过观测不同Yb3+离子浓度条件下共掺Tm3+/Yb3+∶LaF3样品的荧光光谱,研究了Yb3+离子掺杂浓度对于Tm3+离子的荧光发射的影响,并探讨了产生这种现象的原因.研究结果显示,对于1G4→3H6跃迁产生的荧光发射(474 nm),当Yb3+离子浓度增大时,反向能量传递速率的增加导致了荧光强度的增大.然而,当Yb3+离子浓度增大到一定程度时,Yb3+离子激发态能级寿命的减少将引发荧光强度的下降.相比较而言,Yb3+离子的浓度的变化对于1D2→3F4跃迁产生的位于450 nm处荧光强度的影响较弱. 相似文献
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Jingyang WangTianjin Zhang Ruikun PanZhijun Ma Jinzhao Wang 《Physica B: Condensed Matter》2012,407(1):160-164
Ho3+ doped Ba0.65Sr0.35TiO3 (BST) nanocrystals was prepared by sol-gel method. The structural and morphological properties of the nanocrystals were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The absorption spectrum, photoluminescence spectrum and fluorescence time decay curve were measured at room temperature. Based on the Judd-Ofelt (J-O) theory, the J-O intensity parameters Ωt (t=2, 4, 6) of Ho3+ doped BST nanocrystals were calculated to be 0.67×10−20 cm2, 1.11×10−20 cm2 and 1.09×10−20 cm2, respectively. The emission probabilities, radiative lifetimes and branching ratios of the different Ho3+ transitions were also determined. The emission cross sections of the important intermanifold transitions 5F4,5S2→5I8, 5F5→5I8 and 5F4→5I7 have been calculated from the luminescence spectrum. The room temperature fluorescence lifetime of the 5S2→5I8 transition for Ho3+ in BST nanocrystals was measured and the radiative quantum efficiency was estimated to be 61.9%. 相似文献
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Polarized micro-Raman spectra of a 0.65PbMg1/3Nb2/3O3-0.35PbTiO3 (0.65PMN-0.35PT) single crystal poled in the [001] direction are obtained in a wide frequency range (50-2000 cm-1) at different temperatures. The best fit to the Raman spectrum at 77 K is achieved using 17 Lorenzians to convolute into it, and this is proved to be a reasonable fit. According to the group theory and selection rules of overtone and combinational modes, apart from the seven Raman modes that are from first-order Raman scattering, the remaining ones are attributed to being from second-order Raman scattering. A comparison between the experimental results and theoretical predictions shows that they are in satisfactory agreement with each other. Our results indicate that at 77 K the sample belongs to the rhombohedral symmetry with the C3v5 (R3m) space group (Z=1). In our study, on heating, the 0.65PMN-0.35PT single crystal undergoes a rhombohedral to tetragonal to cubic phase transition sequence. The two phase transitions occur at 340 and 440 K, which correspond to the disappearance of the soft mode near 106 cm-1 recorded in VV polarization and the vanishing of the band around 780 cm-1 in VH polarization, respectively. 相似文献
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T.Y. Ko 《Journal of luminescence》2009,129(12):1747-6635
In this report, methods of solvothermal synthesis of Sb2Se3 nanorods from a single-source precursor Sb[Se2P(O iPr)2]3 were demonstrated. The synthesized Sb2Se3 nanorods were expected to have new optical and electrical properties. With the electron beam (E-beam) lithography and focus ion beam (FIB) techniques, we achieved immobilization and positioning of a single Sb2Se3 nanorod on a patterned template. By using the confocal Raman microscope and two-point-contact electrical measurement methods, we obtained optical and electrical characteristics from a single Sb2Se3 nanorod. 相似文献
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The paper presents the results of a study of the influence of heavy ions Xe22+ on the morphology, phase composition, structural and conductive characteristics of CoO/Co0.65Zn0.35 nanowires obtained by the method of electrochemical synthesis. As a result of the research, it was established that an increase in the irradiation fluence leads to a change in the phase composition, due to the decomposition of the oxide phase CoO and the predominance of Co0.65Zn0.35 substitution in the structure of the cubic phase of solid solution. It has been established that an increase in the irradiation fluence and a decrease in the oxide phase in the structure leads to a decrease in the concentration of dislocations and vacancies in the nanowires, which indicates a partial relaxation of defects as a result of irradiation. It is established that a change in dislocation and vacancy density leads to an increase in the value of specific conductivity and a decrease in resistance. 相似文献
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The uniform BaMoO4 and BaWO4 nanoparticles (NPs) have been successfully synthesized by solution route – the direct precipitation of Ba(NO3)2 and Na2MO4 (M = Mo and W) in ethylene glycol under 24 h stirring. The XRD patterns and SEM images proved that the products were tetragonal structured BaMoO4 and BaWO4 with uniform round nanoparticles. Shape, average particle size and particle-size distribution of products were analyzed by TEM – showing the round nanoparticles with the average size of 31.52 ± 4.65 nm for BaMoO4, and 59.77 ± 9.61 nm for BaWO4. The room temperature photoluminescence (PL) indicated that the products have strong blue emission centered at 441 nm – excited with 280 nm wavelength for BaMoO4 NPs, and strong violet emission centered 378 nm – excited with 344 nm wavelength for BaWO4 NPs. These PL behaviors attributed the existence of intrinsic transitions in the [MO4]2- (M = Mo and W) tetrahedrons of their crystal lattices. 相似文献
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Ramphal Sharma Anil Ghule R. Joshi J.C. Vyas T. Ganesh Wonjoo Lee 《Applied Surface Science》2009,255(18):8158-8163
Nanocrystalline CuIn3Se5 thin films have been grown on ITO glass substrates using chemical ion exchange reactions with CdS, in alkaline medium at pH 11. The as-deposited films were annealed in air at 200 °C for 30 min and characterized using X-ray diffraction (XRD), transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy to study the structural, compositional and morphological properties. The XRD patterns reveal the nanoparticles size to be of 18-20 nm diameter, while from the SEM images the nanoparticles size is estimated to be 20-30 nm. It is observed that the annealed films contain nanocrystallites connected with each other through grain boundaries, with grain size of about 100-125 nm and have an overall n-type electrical conductivity and higher photoconductivity. The current-voltage (I-V) characteristics (in dark and light) of these films indicated the formation of a Schottky like junction between the n-CuIn3Se5 (OVC) and CdS/ITO layers. 相似文献
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在镀有Mo的纳钙玻璃衬底上顺序溅射沉积CuGa/In/CuGa层,然后在真空下520 oC硒化40 min,制备成CIGS薄膜. 通
过调整预制层的底层和表层的溅射沉积CuGa层的厚度比,制备不同的CIGS薄膜. 通过X射线衍射谱、拉曼谱、电子能谱、平面和断面SEM的分析, 揭示出CIGS薄膜是黄铜矿相的结构, 晶粒0.5~2 μm,且由硒化CuGa/In/CuGa厚度比为7:20:3的金属预制层后的CIGS薄膜的结晶性最好. 拉曼光谱表明,没有In-Se二元化合物相和有序缺陷化合物相. 相似文献
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In this paper we report the leakage current,ferroelectric and piezoelectric properties of the YFe O3film with hexagonal structure,which was fabricated on Si(111)substrate by a simple sol-gel method.The leakage current test shows good characteristics as the leakage current density is 5.4×10-6A/cm2under 5 V.The dominant leakage mechanism is found to be an Ohmic behavior at low electric field and space-charge-limited conduction at high electric field region.The P–E measurements show ferroelectric hysteresis loops with small remnant polarization and coercive field at room temperature.The distinct and switchable domain structures on the nanometer scale are observed by piezoresponse force microscopy,which testifies to the ferroelectricity of the YFe O3film further. 相似文献
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制备了四元铁磁性Heusler合金Co50Ni22Ga28 sub>:Fex(x=0,1.5,2,2.5),发现材料具有很好的机械性能,在加压、 弯曲和扭曲时都展现出很好的超弹性.室温时,在压力作用下,Co50Ni22< /sub>Ga28:Fe2单晶样品在[001]和[110]方向分别具有约4%和 6.7%的完全可恢复应变.Co50Ni22Ga28:Fe1.5 sub>单晶样品在室温下沿[001]和[110]方向的应力与应变σ-ε曲线的平台部分较缓, 但升温到100℃时,σ-ε曲线中表示超弹性应变的平台变平.Co50Ni22Ga28 :Fe2.5成分的单晶在[001]方向可得到5.5%的超弹性应 变.同时以上材料都显示出了明显的弹性各向异性.
关键词:
铁磁性Heusler合金
超弹性
50Ni22Ga28:Fex')" href="#">Co50Ni22Ga28:Fex 相似文献