溶胶-凝胶法制备的GeO2-SiO2凝胶玻璃的红光发射

以3三氯锗丙酸和正硅酸乙酯为原料采用溶胶凝胶法制备了GeO2SiO2凝胶玻璃.室温下以532nm激光(Nd:YAG)激发GeO2SiO2凝胶玻璃有一强的发光峰,这种发光有两个发光带,其峰位分别在575nm和624nm.该发光现象是由镶嵌在GeO2SiO2凝胶玻璃中GeO2纳米颗粒产生的.利用吸收光谱和TEM对GeO2SiO2凝胶玻璃进行了表征,结果发现随着Ge含量的增加凝胶玻璃中GeO2纳米颗粒的尺寸越来越大,吸收边向低能边移动.X射线衍射和电子衍射确定GeO2SiO2凝胶玻璃中GeO2颗粒的结构为非晶结 关键词： GeO2-SiO2凝胶玻璃 溶胶-凝胶法 红光发射     

溶胶-凝胶软石印法制备Zn2SiO4:Mn图案化薄膜及其发光性能的研究

采用溶胶-凝胶法制备了Zn2SiO4:Mn薄膜并结合毛细管微模板技术实现了薄膜的图案化,利用X射线衍射(XRD),原子力显微镜,光学显微镜,发光光谱等手段对Zn2SiO4:Mn的结晶过程、发光性质进行了研究.XRD结果表明,溶胶-凝胶法合成的样品在800℃时已开始结晶,在1000℃时可得到纯相的Zn2SiO4:Mn,这比传统的固相法的烧结温度低150℃.Zn2SiO4:Mn薄膜的激发光谱在220nm和280nm之间有一个强的吸收峰,峰值位于248nm,发射光谱的最大值位于522nm,为绿光发射.从原子力显微镜照片可知组成薄膜的粒子比较均匀,其平均直径为220nm.我们获得了四种图案化宽度,分别是5,10,20,50μm.光学显微镜的结果表明,图案薄膜烧结后相对于烧结前有10%～20%的收缩.     

在硅片上沉积厚二氧化硅的火焰水解法研究

用火焰水解和高温烧结的方法在单晶硅基片上制备了厚SiO2和B2O2-P2O2-SiO2光波导包层材料。并用扫描电镜(SEM)和X射线粉末衍射(XRD)方法对其微观形貌和物相结构进行了观察和检测。重点对硅基片上沉积厚SiO2时的龟裂和析晶问题进行了深入研究。从扫描电镜照片可以看出．火焰水解法形成的SiO2粉末呈多孔的蜂窝状结构。这种粉末具有很高的比表面积,因而很容易烧结成玻璃。X射线衍射图谱表明．这种粉末是完全非晶态的。经过烧结以后,从扫描电镜照片可以明显看出硅基片上的SiO2薄膜出现龟裂。同时,X射线衍射测试结果表明有少量SiO2析晶。而通过在SiO2中掺入B2O3、P2O5,上述龟裂和析晶完全消失。用这种工艺制备的SiO2波导包层材料厚度达到20μm以上,表面光滑、没有龟裂,而且是完全玻璃态的,可以用于制备性能优良的各种硅基二氧化硅波导器件。     

溶胶凝胶软石印法制备Zn_2SiO_4∶Mn图案化薄膜及其发光性能的研究

采用溶胶 凝胶法制备了Zn2SiO4∶Mn薄膜并结合毛细管微模板技术实现了薄膜的图案化,利用X射线衍射(XRD),原子力显微镜,光学显微镜,发光光谱等手段对Zn2SiO4∶Mn的结晶过程、发光性质进行了研究。XRD结果表明,溶胶 凝胶法合成的样品在800℃时已开始结晶,在1000℃时可得到纯相的Zn2SiO4∶Mn,这比传统的固相法的烧结温度低150℃。Zn2SiO4∶Mn薄膜的激发光谱在220nm和280nm之间有一个强的吸收峰,峰值位于248nm,发射光谱的最大值位于522nm,为绿光发射。从原子力显微镜照片可知组成薄膜的粒子比较均匀,其平均直径为220nm。我们获得了四种图案化宽度,分别是5,10,20,50μm。光学显微镜的结果表明,图案薄膜烧结后相对于烧结前有10%～20%的收缩。     

在SrTiO3基底上用溶胶-凝胶法制备CeO2缓冲层

CeO2是目前被广泛研究的能与YBCO超导材料有良好晶格匹配的缓冲层材料,溶胶-凝胶法是一种成本低廉的非真空制备薄膜的方法,如果能用这种方法制备质量良好的CeO2薄膜,则可降低YBCO覆膜导体制备的成本.本文通过一种以Ce(NO3)3*6H2O为先驱液相的溶胶体系,在SrTiO3(100)基底上用溶胶-凝胶方法制备了CeO2薄膜.研究了不同热处理温度对CeO2薄膜晶粒生长的影响.为了避免CeO2薄膜表面微裂纹的形成,研究了在烘干和热解过程中所采用的有效方法.利用TGA,DSC,SEM和XRD,对CeO2薄膜的吸热放热过程、表面形貌和相组成进行了分析.结果表明,该溶胶经旋涂、120℃下烘干以及直接300℃热解后,再在600℃下烧结,可制得无裂纹和孔洞、表面质量良好的CeO2薄膜.     

采用溶胶-凝胶法制备nc-Si/SiO2薄膜

溶胶-凝胶方法是近年发展起来的一种新型的材料制备技术，被广泛的应用于薄膜、均匀超细粉末和陶瓷涂层的制备中。本文以正硅酸乙酯(TEOS)为原料，在乙醇共溶剂和盐酸催化剂条件下，采用溶胶-凝胶方法制备含有纳米晶硅（nc-Si）的SiO2胶体溶液，通过旋涂法使溶剂迅速挥发而迅速凝胶化，经过适当温度的干燥和烧结制备了nc—Si／SiO2薄膜。探讨了胶体粘度、盐酸催化剂浓度、旋涂速度和时间对成膜质量的影响。给出了nc—S／SiO2薄膜的扫描电镜图像和表征nc-Si／SiO2薄膜组分的能谱图。     

四取代4-异丙苯基苯氧基酞菁铅复合凝胶玻璃的结构及光限幅性能研究

采用溶胶-凝胶(Sol-gel)湿化学工艺将四取代4-异丙苯基苯氧基酞菁铅PbPc(CP)₄掺入二氧化硅(SiO₂)凝胶玻璃基质,制备均匀掺杂的PbPc(CP)₄复合凝胶玻璃,并通过紫外-可见(UV-Vis)吸收光谱和透射电镜(TEM)图像对PbPc(CP)₄在复合凝胶玻璃中的存在状态及结构进行了表征。对PbPc(CP)₄在液相体系和固相体系中的光限幅性能分别进行了测试及对比研究。结果表明PbPc(CP)₄以团簇形式存在于复合凝胶玻璃中,并由于钢性结构固相基质的保护作用使其在复合凝胶玻璃相对于液相体系中表现出较强的光限幅特性。     

Er硅酸盐化合物薄膜的相转变和光致发光特性研究

溶胶-凝胶法在Si(100)基片上旋涂法制备铒硅酸盐化合物（Er silicate）薄膜.系统研究了烧结温度和烧结时间对Er silicate薄膜相结构、相转变以及光致发光特性的影响.在1000 ℃以下,薄膜晶体结构为Er₂O₃ 晶体和SiO₂ 非晶的混合物.随着烧结温度增加到1200 ℃,保温时间增加到30 min,薄膜晶体结构转变成(100),(200)和(300)择优取向的Er₂SiO₅相. 关键词： 发光学 光学薄膜 溶胶-凝胶法 铒硅酸盐     

以Eu-苯甲酸-1,10-菲咯啉为掺杂剂的SiO2,SiO2-B2O3和SiO2-B2O3-Na2O体系材料的结构及Eu3+的发光性质

用溶胶-凝胶法制备以Eu-苯甲酸-1,10-菲咯啉为掺杂剂的SiO2,SiO2-B2O3和SiO2-B2O3-Na2O为基质的发光材料.材料经1000℃退火处理后,结构十分稳定.通过激发光谱和发射光谱、红外光谱、TEM、XRD研究了基质结构对Eu3 发光性能的影响.结果显示:在589和614 nm处显示Eu3 的特征发射带,对应于Eu3 的5D0→7Fj(j=1,2)跃迁;与直接掺入EuCl3的玻璃材料相比,以Eu-苯甲酸-1,10-菲咯啉为掺杂剂的玻璃材料,虽然Eu的掺杂量较小,但Eu的发光强度较大.与以SiO2为基质的玻璃材料相比,以SiO2-B2O3为基质的玻璃材料Eu3 的发光减弱,其红外光谱显示形成Si-O-B键,说明该结构对Eu3 的发光有猝灭作用,以SiO2-B2O3-Na2O为基质的玻璃材料Eu3 的发光明显增强,其红外光谱显示不存在SiOB键的振动吸收,可能是Na取代B的位置,形成Si-O-Na键,此结构对Eu3 的发光有一定的增强作用.     

微模塑法制备PMMA/SiO2二氧化硅杂化材料微结构

以摩尔比为 1∶1的甲基丙烯酸甲酯 (MMA)、甲基丙烯酸 (3 三乙氧基硅烷基 )丙酯 (ESMA)单体、0 .2 %(单体总量的质量分数 )的偶氮二异丁腈AIBN引发剂和四氢呋喃 (THF)溶剂 ,及 2 0 % (总质量分数 )的正硅酸乙酯TEOS合成出PMMA/SiO2 有机 无机杂化的杂化溶胶 .将溶胶在洗净的普通光学玻璃基片表面甩膜 .利用软刻蚀中的微模塑法 ,把有机硅弹性印章复制有精细图纹一面轻放在杂化溶胶膜上进行微模塑 ,外加 1N压力于12 0℃下处理 2h使溶胶凝胶化 .印章剥离后在基片表面就形成了PMMA/SiO2 有机 无机杂化材料的微图纹结构 .从微图纹的光学显微镜照片可以看出微模塑方法制备杂化材料复制的图纹精细度高 ,操作简单易行 ,是一类比较理想的微细图纹结构加工的方法 .     

Speckle characteristics of a broad-area VCSEL in the incoherent emission regime

We present a technique to reduce the speckle contrast of a NIR broad-area VCSEL based on the spatially incoherent emission regime that can be obtained when using the proper driving conditions. We evaluate the efficiency of this technique to reduce the speckle contrast by comparing it with the speckle characteristics in multimode emission under cw operation. Depending on the illumination setup, the incoherent emission regime can lead to a strongly reduced speckle contrast down to 1.3%. This is in agreement with estimates of the expected speckle contrast reduction when three contrast reducing effects are taken into account. These low contrast values make the investigated sources attractive for several applications that suffer from speckle noise.     

Structural characterization of ultrathin Cr and Sc films for soft X-ray mirrors

The structure of multilayers of ultrathin scandium (Sc) and chromium (Cr) films has been characterized by means of transmission electron microscopy (TEM). Face centered cubic Sc was found both in magnetron sputtered thin Sc layers on Si(0 0 1) and in Cr/Sc multilayers for soft X-ray mirrors. The single Sc and Cr layers are polycrystalline with randomly oriented grains, while Sc and Cr within the Cr/Sc multilayer show a strong [0 0 1] texture in the deposition direction. From high-resolution images the orientation-relationship at the Cr/Sc interfaces could be deduced as: Sc_[110]//Cr_[100] and Sc_[010]//Cr_[110], which was confirmed by image simulations.     

Optical transmission through an interface between subwavelength slits

This paper studies optical transmission through an interface between two slits with different widths in a sheet composed of an ideal conductor. Such a structure is of potential use in fabricating optical diode and may be the simplest one compared to other designs. Our calculations show that there is a critical wavelength. When the light wavelength is below the critical wavelength, the transmissivity is unidirectional. The expression of the stable transmissivity as a function of the ratio of the widths of the two slits was obtained analytically. Particularly, at the critical wavelength, the transmissivities are zero. This phenomenon has great potential for application in the manufacture of wavelength blockers.     

Effect of Ir(pq)2acac doping on CBP in phosphorescence organic light-emitting diodes

Doping is one of the most powerful methods amongst the various performance improvement ways. Doping affects the energy levels of the host layer by the energy level of the dopant. This allows the energy bandgap to be adjusted to a desired level and thus generates light corresponding to that energy level. Alternatively, it can act as an energy barrier between the interfaces to change the flow of carriers. In this study, the voltage dependences of undoped and doped devices were observed. Bis(2-phenylquinoline) iridium(III) (acetylacetonate) (Ir(pq)₂acac) was doped in 4,4′-N, N′-dicarbazole-biphenyl (CBP) as the emission layer. The light intensity changes with the doping concentration, and the efficiency was also studied. When a high voltage was applied, the effect of triplet-triplet annihilation (TTA) adversely affected the electron-hole recombination. We analyzed the optimal operating conditions and the effect of doping concentration on OLEDs.     

Belle实验观测到新类粲偶素结构

利用在Υ(nS)(n=1,2,4,5)共振态及其附近采集的大量数据,Belle实验测量了末态中含两个矢量粒子的双光子过程γγ→J/ψ和ωJ/ψ.在这两个过程中,发现了两个窄共振结构X(4350)和X(3915).这两个新结构的性质目前尚不清楚,可能是普通粲偶素粒子,也可能是含一对粲夸克和一对轻夸克的四夸克态,或含一对粲夸克和一个激发胶子的混杂态,或是由其他未知的动力学原因造成的奇特结构.Belle同时发现在γγ→J/ψ过程中,不存在显著的Y(4140)的信号,实验结果与将Y(4140)解释为四夸克态的部分理论预期有较大差异.     

Grain boundary potential and charge density at grain boundaries of chemically prepared thin silver sulfide films

The grain boundary potential and interface state charge density at the grain boundaries of silver sulfide (Ag₂S) thin films prepared by chemical conversion of cadmium sulfide (CdS) films have been determined from the dc resistance of the material and are found to be sensitive to annealing. A reduction in the grain boundary potential and the grain boundary charge density of the film has been noticed when the source CdS film is annealed at different temperatures prior to chemical conversion. The variation in the grain boundary charge density of the grown Ag₂S film with source annealing temperature has been found to be similar to that of thin cadmium sulfide film, reported earlier. An additional low temperature heat treatment of the sample results in an enhancement in the charge density at the grain boundaries. The change in the silver vacancy and/or oxygen and sulfur content of the films as revealed from the energy dispersive spectra of the films suggests possible role of film composition on the grain boundary charge density.     

XYZ particles at Belle

In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X(3872), X(3915),Y(4140), X(4350), and the charged Z states.     

三螺旋DNA分子Poly(dT)·Poly(dA)·Poly(dT)碱基振动模式

利用晶格动力学方法计算了三螺旋 DNA分子 poly(d T)· poly(d A)· poly(d T)碱基振动模式 ,并根据势能分布矩阵对碱基振动模式进行了指定。计算的模式频率同拉曼光谱实验相符合     

Effect of swift heavy ion irradiation on photoluminescence properties of ZnO/PMMA nanocomposite films

We report a study on the SHI induced modifications on structural and optical properties of ZnO/PMMA nanocomposite films. The ZnO nanoparticles were synthesized by the chemical route using 2-mercaptoethanol as a capping agent. The structure of ZnO nanoparticles was confirmed by XRD, SEM and TEM. These ZnO nanoparticles were dispersed in the PMMA matrix to form ZnO/PMMA nanocomposite films by the solution cast method. These ZnO/PMMA nanocomposite films were then irradiated by swift heavy ion irradiation (Ni⁸⁺ ion beam, 100 MeV) at a fluence of 1×10¹¹ ions/cm². The nanocomposite films were then characterized by XRD, UV-vis absorption spectroscopy and photoluminescence spectroscopy. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. Enhanced green luminescence at about 527 nm and a less intense blue emission peak around 460 nm were observed after irradiation with respect to the pristine ZnO/PMMA nanocomposite film.     

The effect of phonon anisotropic scattering on the thermal conductivity of silicon thin films at 300K and 400K

Previous studies have shown that anisotropy in phonon transport exist because of the difference in phonon dispersion relation due to different lattice directions, as observed by a difference in in-plane and cross-plane thermal conductivities. Our current work intends to study the effect of anisotropy scattering on silicon thermal conductivity at 300 K and 400 K. We adopt the Henyey and Greenstein probability density function in our phonon Monte Carlo simulation to investigate the effect of highly forward and backward scattering events. The impact of applying the anisotropy scattering using this approach is discussed in detail. While the forward and backward scattering will increase and decrease thermal conductivity respectively, the extent of the effect is non-linear such that forward scattering has a more obvious effect on thermal conductivity than backward scattering.