Ho3+/Yb3+共掺的SiO2-Al2O3-BaO-BaF2微晶玻璃上转换发光研究

制备了Ho3+/Yb3+共掺的氧氟硅酸盐玻璃, 根据玻璃样品的差热分析进行微晶化处理, 测试了Ho3+/Yb3+共掺微晶玻璃的X射线衍射(XRD)图谱、吸收光谱和上转换发光光谱。结果发现, 在980 nm LD激发下, Ho3+/Yb3+共掺的含BaF2纳米晶的氧氟硅酸盐微晶玻璃可以同时观察到绿光(544 nm)和红光(656, 748 nm)上转换发光, 分别对应于Ho3+ 离子的5F4/5S2→5I8, 5F5→5I8和5F4/5S2→5I7能级跃迁, 与未热处理的玻璃样品相比, 微晶玻璃样品的绿光发光强度增强约347倍。研究结果表明含BaF2纳米晶的氧氟硅酸盐微晶玻璃是一种潜在的上转换基质材料。     

荧光粉Sr2SiO4:Eu2+中不同格位发光研究

采用高温固相反应法制备了Sr₂SiO₄:xEu²⁺荧光粉,研究Eu²⁺所占据的 Sr₂SiO₄中Sr1和Sr2两个不同格位及掺杂浓度和激发波长对格位发光的影响。荧 光粉发射光谱为一双峰的宽发射光谱,可拟合为峰值位置位于480nm 和530nm的两条高斯曲线,分别对应Eu²⁺所占据的Sr1和Sr2两 个不同格位的发射。随着 Eu²⁺掺杂浓度增加,Sr1和Sr2格位的发光强度均出现浓度猝灭现象,Sr2格位的 长波长发射峰出现明显红移现象,而Sr1格位的短波长发射峰发生红移-蓝移-红 移现象,这与Sr1和Sr2格位的优先占据以及格位间能量传递有关。随着激发波 长的增加,Sr2格位的长波长发射的发光强度与Sr1格位的短波长发射的发光强 度比值增加,占据不同格位的Eu²⁺对不同激发波长表现出明显的选择激发效应。     

CaSi2O2N2:Ce3+/Eu2+荧光粉的发光性能研究

采用高温固相反应法制备了CaSi₂O₂N₂:C e³⁺/Eu ²⁺荧光粉,研究了分别掺杂Ce³⁺、Eu²⁺及Ce³⁺/Eu²⁺共掺 杂时荧光粉 的发光特性。CaSi₂O₂N₂:Ce³⁺在333 nm激发下得到宽波段的发射谱,发射峰 位于395nm,随着Ce³⁺浓度的增大,发 射波长出现明显的红移,猝灭浓度为1mol%。CaSi₂O₂N₂:Eu²⁺在397nm激发下得到峰值位于540nm处的宽波段发射谱, 猝灭浓度为1mol%。对于Ca0.99－2xSi₂O₂N₂:xCe ³⁺,xLi⁺,0.01Eu²⁺荧光粉,在333nm激发下,位于395nm处的发射峰十分微 弱,在540nm处有宽带发射,随着Ce³⁺浓度增大,位于540nm处的Eu²⁺的特征 发射显著增强。对于Ca0.98－ySi₂O₂N₂: 0.01Ce³⁺,0.01Li⁺,yEu²⁺荧光粉,在激发光波长 为333nm,Eu²⁺浓度较低时,可以观察到两个发射带,峰值分 别位于395nm及540nm,随着Eu²⁺浓度增加,位于395nm的 发射强度一直减小,而540nm处的发射强度先增加后减小,猝灭浓 度为0.4mol%。证实了Ce³⁺,Eu²⁺之间发生了有效的能 量传递。计算出Ce 3+、Eu²⁺之间能量传递的效率ηT,在Eu²⁺浓 度为 1mol%时ηT趋于饱和,达到97.7%。通过计算,得到Ce3+ 与Eu²⁺之间的能量传递方式为电偶极-电偶极相互作用。     

Yb3+: GdGaGe2O7制备、结构及光谱性能

采用固相法制备了10at.% Yb3+: GdGaGe2O7多晶粉体,通过X射线粉末衍射用Rietveld全谱拟合给出了其空间群为P21/c,晶格常数a、b、c和β、Gd/Yb和Ga的原子坐标为。Ge1、Ge2、O1～O7的原子坐标。通过吸收谱、激发谱、光致发光谱和Raman光谱确定Yb3+的晶场能级分裂;1003nm发光在低温8K和室温(300K)时上能级荧光寿命为0.493ms和0.774ms。在室温下测量荧光寿命变长主要由再吸收所引起。Yb3+:GdGaGe2O7的吸收和发射光谱均很宽,荧光寿命长,是潜在的全固态激光工作物质。     

Li+增强Ho3+/Yb3+:Y2O3纳米晶的上转化发光研究

采用凝胶溶胶法制备了不同浓度的Y2O3:Ho3+/Yb3+/Li+纳米晶,并且系统研究了不同掺杂浓度对上转化荧光现象的影响。首先,通过XRD图形判断了晶体结构的生成,再通过980 nm的激光器和荧光光谱仪测得的光谱图,发现了位于520~579 nm的绿光、635~674 nm的红光等两条很强的可见光,还有一条较弱的位于743~775 nm的近红外发光。最后,通过与能级图比较和分析可以得出:它们分别是5F4/5S2→5I8,5F5→5I8和5F4/5S2→5I7荧光跃迁。可以看出:在掺杂入Li+之后,上转化荧光得到了极大增强。     

毛竹茎秆纤维发育过程中Ca~(2+)-ATPase分布的动态变化

采用超微细胞化学定位方法,对毛竹茎秆纤维发育过程中Ca2 -ATPase分布的动态变化进行了研究.在原始细胞形成期,Ca2 -ATPase活性产物主要分布在质膜、核染色体、染色质及核仁上.在初生壁形成早期,质膜上Ca2 -ATPase活性增强;随着纤维细胞的逐渐液泡化,液泡膜、细胞质、质膜内陷和同心圆潴泡上逐渐出现Ca2 -ATPase活性产物的分布;在初生壁形成后期,液泡膜上的Ca2 -ATPase活性增强,在运输小泡上出现Ca2 -ATPase活性产物分布,质膜、细胞质、染色质和核仁上始终具有较强的Ca2 -ATPase活性.随着次生壁的形成,纤维细胞发生程序性死亡(PCD),在质膜、胞间连丝和降解的液泡膜、细胞质、核染色质上具有较强Ca2 -ATPase活性;随着次生壁的逐渐增厚,大量具有Ca2 -ATPase活性的运输小泡在前四年中持续存在,以后逐渐减少;而在六年生茎秆纤维细胞的质膜、胞间连丝、凝聚的核染色质和降解的原生质体中始终具有Ca2 -ATPase活性.结果表明,ca2 -ATPase参与了毛竹茎秆纤维细胞的增殖过程、细胞壁形成过程及PCD过程中原生质体的降解.     

Er3+,Yb3+:glass/Co2+:MgAl2O4复合材料LD泵浦被动调Q微型激光器

报道了一种应用于激光测距的Er³⁺,Yb³⁺:glass/Co²⁺:MgAl₂O₄复合材料LD泵浦的被动调Q微型激光器。 采用玻璃与晶体复合技术,将增益介质Er3＋/Yb3＋共掺 磷酸盐玻璃和被动调Q可饱和 Co²⁺:MgAl₂O₄晶体进行了光学热复合,复合材料会降低增益介质内部的温度梯度 ,使热焦距变长,模体积 增加,激光光束质量提高;另外,复合材料使腔内损耗减小,腔内的粒子数密度提高,脉宽 变窄,输出能 量增加,从而激光器性能得到提高。在重复频率为10Hz情况下,采 用中心波长为940nm的单管LD作为泵 浦源,获得单脉冲能量为210μJ、脉冲宽度为2.8ns,峰值功率大于70kW的波长为1.5 μm的被动调Q激光输出,光束质量为1.2     

纳米粉体Y2O3:Ti 3+ , Eu3+的光谱性能

采用共沉淀法在氮氢气氛中制备出Y₂O ₃:Ti ³⁺, Eu ³⁺纳米粉体,测量了它的XRD、激发与发射光谱,观测了形貌。通过与Y₂O ₃:Ti ³⁺纳米粉体的光谱比较分析,发现Y₂O ₃中的Ti ³⁺至Eu³⁺存在能量传递,以致紫外至蓝光区域的光,均能使Eu³⁺经5D0→7F2等跃迁通道发射出610nm左右的荧光,于是增强了粉体在红橙光区发光的比重,因此可以调节粉体的发光性能。Y₂O ₃:Ti ³⁺纳米粉体的吸收带从紫外延伸到蓝光区,强荧光带覆盖了整个可见光区,这预示它有望成为新一代白光LED或汞灯的光转换荧光粉。     

Al3+/Eu2+共掺杂高硅氧玻璃的荧光特性

由纳米多孔玻璃制备了Al3+/Eu2+共掺杂的高硅氧玻璃,并研究了在纳米多孔玻璃基质中共掺杂Al3+离子对Eu2+离子450 nm处蓝色荧光强度和荧光峰位的影响。结果表明,共掺杂Al3+离子可分散多孔玻璃中丛聚的Eu2+离子,加之Al2O3较低的声子能量,使Eu2+离子的蓝色荧光发射显著增强;并且由于共掺杂的Al3+降低了Eu2+离子5d轨道劈裂幅度,随着Al3+离子含量的增加,Eu2+离子荧光峰蓝移。     

H2+和D2+谐波强度与波长的关系

为了了解H₂+及其同位素分子谐波光谱效率与激光波长之间的关系,采用求解2维薛定谔方程的方法,理论研究了600nm~1600nm激光波长下H₂+和D₂+谐波光谱强度随波长的变化关系。结果表明,光谱强度随波长增大而减小;在短波长区间,H₂+光谱强度减小的倍率要大于D₂+,在长波长区间,H₂+光谱强度减小的倍率要小于D₂+;此外,在弱光强下,H₂+光谱强度总是大于D₂+, 在强光强下,H₂+光谱强度在短波长区间小于D₂+, 而其在长波长区间大于D₂+; 核间距延伸和电荷共振增强电离在H₂+和D₂+谐波光谱强度变化上起到主要作用。这一结果对分子谐波调控是有帮助的。     

Fluorescence enhancement of single-phase red-blue emitting Ba3MgSi2O8:Eu2+,Mn2+ phosphors via Dy3+ addition for plant cultivation

Fluorescence enhancement of red and blue concurrently emitting Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺ phosphors for plant cultivation has been investigated by Dy³⁺ addition. The Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺,Dy³⁺(BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm. The two emission bands are coincident with the absorption spectrum for photosynthesis of plants. An obvious enhancement effect has been observed upon addition of Dy³⁺ with amount of 0.03 mol%, in which the intensities of both blue and red bands reach a maximum. The origin of red and blue emission bands is analysed. The photochromic parameters of the samples at the nearly UV excitation are tested. This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation. This work has been supported by National Natural Science Foundation of China (Grant No 50872091) and the Natural Science Foundation of Tianjin, China (06YFJMJC02300, 06TXTJJC14602).     

Characteristics of siliconn+-n--n+ diode with sub-micrometer n- region

In this paper, the I-V characteristics of silicon n⁺-n ^--n⁺ diode are investigated as a parameter of the length of the n^- region. This diode with shorter n^- region than 1 μm has the ohmic characteristics until reaching high electric field in spite of the existence of numerous space-charges in the n^- region, for the first time in this report. This conductance of the diode is inversely proportional to the third power of the length of the n^- region. The experimental results are in good agreement with an analytical calculation including the diffusion term of carriers injected from the n+ regions to the n^- region. However, the diode with longer n^- region than 2 μm shows the space-charge-limited conduction which is the same as earlier reports     

Effect of electron cyclotron resonance H+,Ne+, Ar+, and Xe+ plasma precleaning ontitanium silicide formation

A vacuum integrated cluster tool process incorporating electron cyclotron resonance plasma cleaning, Ti sputter deposition, and rapid thermal annealing in N₂ is used to form a TiN_x<1/TiSi_y bilayer on (100) Si where the film composition is controlled by the preclean chemistry. Chemical cleaning with nominal 10 eV H⁺ completely removes native Si oxide resulting in a hydrogen terminated surface that promotes silicidation compared to one cleaned with buffered-oxide-etching (BOE). If the native oxide is only partially reduced, viz., SiO_x<2 surface, for example by shortening the H⁺ exposure time, then silicidation is largely inhibited and a thicker nitride layer is formed. Sputter cleaning with 50 to 250 eV Ar⁺ results in a bilayer that is roughly equivalent to that formed with BOE, whereas 50 to 150 eV Xe⁺ bombardment favors nitridation. Precleaning with >150 eV Ne⁺ promotes silicidation, thereby minimizing nitride thickness. The effects of precleaning are significant as the activation energy for TiSi_y formation is reduced from 1.8 eV characteristic of a BOE cleaned surface to 1.2 eV on Si etched with 250 eV Ne⁺. Mechanistically, the silicide kinetics are shown to be inhibited by the presence of a thin amorphous layer that is formed only when cleaning Si with Ar⁺ and Xe⁺ with the effect that both knock-on oxygen atoms and implanted noble gas atoms trapped within the amorphous layer retard the requisite solid-phase epitaxial regrowth kinetics. Recrystallizing the amorphous Si surface prior to metallization appears to restore the near-normal silicide kinetics that is characteristic of Ne⁺ cleaning     

NO分子Α~2Σ~+和Ε~2Σ~+能级的LIF光谱

本文报道了单光子激发NO分子A~2∑~+(υ=0)能级的LIF光谱研究,其观测到A~2Σ~+(o=0)→X~2Ⅱ(1″=0～11)跃迁的12个振动带。运用两步激发的方法,研究了E~2Σ~+(扣=0)能级激发后在紫外波段的LIF光谱,明显测量到了E~2Σ~+(1=0)能级直接跃迁到基态X~2Ⅱ的荧光振动带。     

直流辉光放电HgX(X=Cl,Br,I)B~2∑~+→X~2∑~+发射光谱的研究

蓝绿色激光由于在水下通讯等方面的应用近年来颇受重视,溴化汞激光就是其中的一种,连同氯化汞、碘化汞激光,统称为HgX(X=Cl,Br,Il)激光,其波长在可见波段一定范围内可调(HgCl:552～559nm,HgBr:495～505nm,HgI:443～445nm).激光跃迁B~2∑~+→X~2∑~+的上能态激发可由HgX_2蒸气在紫外光或快放电作用下分解实现:HgX_2→HgX_2(b~1∑_u~+)→HgX(B~2∑~+)+X(~2P).用后一种方式可制成小型、封闭、长寿命器件,但至今只能得到短脉冲(几+ns)输出.本文目的是通过研