氢钝化对低温沉积nc-SiOx/SiO2多层薄膜发光特性影响机制研究

采用等离子体增强化学气相沉积技术实现了nc-SiOx/SiO2多层结构薄膜在220℃的低温沉积,并对其450℃N2+ H2形成气体退火前后的微结构及其发光特性进行了研究.结果表明,直接沉积的纳米硅多层薄膜未观察到较明显的室温发光,而形成气体退火后样品出现峰值位于780 nm附近较强的光致发光,归因于活性氢能有效钝化纳米硅表面悬键,提高了材料的发光强度.结合瞬态发光谱分析,采用量子限制-发光中心模型可以合理解释纳米硅多层结构的发光特性.     

Cu过量对Cu1+x Al1-x O2(0≤x≤0.04)薄膜结构与光电性能的影响

以单相多晶Cu1+x Al1-x O2陶瓷做靶材,采用射频磁控溅射方法在石英衬底上沉积了Cu过量的Cu1+x Al1-x O2(0≤x≤0.04)薄膜.通过X射线衍射(XRD)、紫外吸收光谱以及电导率的测试,表征了不同含Cu量Cu1+x Al1-x O2薄膜的结构与光电性能.结果表明,沉积态薄膜经退火处理后,由非晶转变为具有铜铁矿结构的纯相Cu1+x Al1-x O2;退火态薄膜在可见光区域的平均透过率约为55;,平均可见光透过率不受Cu含量的影响;退火态薄膜样品的室温电导率随Cu含量的增加而增大,Cu1.04 Al0.96 O2的室温电导率最高,为1.22×10-2 S/cm;在近室温区(200～300 K),退火态薄膜均很好地符合Arrhenius热激活模式.     

提高掺铒硅基纳米材料发光效率的探索

本文中,我们以SiO2介质镶嵌的纳米晶Si薄膜(nc-Si/SiO2)作为基质,将稀土离子Er掺入其中所形成的nc-Si:Er3+/SiO2薄膜材料为主,介绍了nc-Si→Er3+之间的能量转移过程,探讨了实现各类掺Er的Si基纳米材料高效率发光的可能途径.这些方法主要包括:增强nc-Si→Er3+的能转移效率,提高有效Er的掺杂浓度,选择最佳的退火温度,增加Er-O发光复合体的浓度和制备新的Er掺杂Si基纳米结构等.这些方法对制备具有高发光效率的掺铒硅基纳米材料具有重要的实际意义.     

Al2O3膜层制备参数对SiO2/Al2O3/PET复合膜透湿性能的影响

采用磁控溅射工艺在PET衬底上依次沉积了Al2 O3和SiO2薄膜,制备出SiO2/Al2 O3/PET复合膜.利用扫描电镜和透湿仪对复合膜的表面形貌和透湿性能进行表征.研究了制备Al2 O3膜层的射频功率、氩气流量、本底真空度和溅射时间4个参数对复合膜透湿率的影响.结果表明:复合膜的透湿率随着本底真空度的升高而减小,随着射频功率、氩气流量和溅射时间的增加均呈现先减小后增大的变化趋势;4个制备参数对复合膜透湿率的影响程度由大到小依次是本底真空度、氩气流量、射频功率、溅射时间;4个制备参数的较优组合为本地真空度0.5×10-3 Pa,射频功率300 W,溅射时间6 min,氩气流量70 mL·min-1.     

反应磁控溅射制备AZO薄膜相结构的演化及机理研究

在室温下,利用直流反应磁控溅射技术在不同的氧气流量下沉积ZnO∶ Al (AZO)薄膜.采用XRD、SEM和TEM技术分析薄膜相成分、表面截面形貌及微观结构.结果表明:氧气流量为2.5 sccm时,沉积形成的薄膜为不透明具有金属导电性能的AZO/Zn( AZO)双层复合膜结构;氧气流量为3.5 sccm时,沉积形成了透明导电的AZO薄膜;氧气流量为5.0 sccm时,形成了透明不导电且含有纳米Al2O3颗粒的AZO薄膜;此外,AZO薄膜在400℃退火后,薄膜晶粒长大和(002)晶面方向择优生长更加明显以及高氧气流量沉积的AZO薄膜中的纳米Al2O3颗粒消失.     

Tb∶Lu2SiO5光学薄膜的结构演变和发光性能

采用溶胶-凝胶法结合旋涂工艺在单晶硅(111)上制备了Tb3+离子不同掺杂浓度的硅酸镥光学薄膜(Tb∶Lu2SiO5),利用热重差热分析(TG-DSC)、X射线衍射(XRD)、傅里叶红外光谱仪(FTIR)、原子力显微镜(AFM)和紫外可见荧光光谱(PL)对Tb∶Lu2SiO5薄膜的不同温度热处理的结构演变和发光性能进行了表征.研究结果表明Tb∶Lu2SiO5光学薄膜表面均匀、平整、无裂纹,薄膜样品从800℃开始晶华,1100 ℃时晶化完全.Tb∶Lu2SiO5的发光性能表现为Tb3+离子的4f→5d和5D4(5D3)→7FJ(J =6,5,4,3)跃迁结果(监测波长分别为480～650 nm和350～470 nm),激发主峰位于～240 nm,发射光谱主峰为542 nm的绿光发射.研究表明Tb3掺杂浓度对Tb∶Lu2SiO5光学薄膜的发光强度会产生明显影响,掺杂15mol;的Tb3+时,Tb∶Lu2SiO5薄膜的发光强度最强.     

SiO2@Gd2O3∶Tb3+核壳微球的可控合成及发光性能研究

采用简便的尿素辅助沉淀法将Gd2O3∶Tb3+成功包覆在二氧化硅微球表面合成了尺寸均匀的球形SiO2@Gd2O3∶Tb3核壳发光材料,解决了稀土发光材料普遍存在的形貌可控性差和颗粒尺寸不均一等问题.利用XRD、SEM、红外光谱和荧光光谱等表征测试了样品的形貌、结构和发光性能.SEM照片和尺寸分布图显示,SiO2@Gd2O3∶Tb3+粒子呈现均匀球形形貌,分散性良好,粒径约(608 +18) nm.XRD图谱分析表明,600℃煅烧后,壳层Gd(OH)3CO3完全转变为立方相Gd2O3,结晶性良好,无杂相生成.同时,结合红外光谱推测了SiO2@Gd2O3∶Tb3核壳微球的形成机理,并得出Gd2O3∶Tb3+壳层主要以Si-O-Gd键形式连接在二氧化硅微球表面.在240 nm紫外光激发下,SiO2@Gd2O3∶Tb3核壳微球呈现绿光发射,其中,位于540 nm处的主峰归属于Tb3+的5D4→7F5能级跃迁.不同Tb3掺杂浓度下的发射光谱表明,当Tb3+掺杂浓度为4mol;时,SiO2@Gd2O3∶Tb3+核壳微球的发射强度达到最大值,寿命为1.55 ms,色坐标位于绿色区域,展现了良好的绿光发光性能.     

透明SiO2-Al2O3-CaO-CaF2 微晶玻璃中Tb3+的发光性能研究

通过对1.0 mol;Tb2O3掺杂45SiO2-20Al2O3-10CaO-25CaF2玻璃进行热处理制备出透明微晶玻璃,经XRD分析微晶玻璃内析出了大小约为27 nm 的CaF2颗粒.并分别在紫外和X射线激发下研究了Tb3+在基质玻璃和透明微晶玻璃中的发光行为.结果表明:微晶玻璃中CaF2纳米晶颗粒的析出有利于提高Tb3+的发光性能,紫外激发时,Tb3+的545 nm特征发光强度增强了4倍;而X射线激发时,Tb3+的545 nm特征发光强度增加了3.5倍.     

SiO2阻挡层对电子束沉积法生长高迁移率IWO薄膜性能的影响

利用电子束沉积技术在玻璃衬底上制备了IWO( In2O3∶WO3)薄膜和SiO2缓冲层,并将SiO2缓冲层对IWO薄膜性能的影响作了探究.SiO2缓冲层在室温生长.SIMS测试表明:SiO2缓冲层能有效阻挡浮法玻璃中的杂质进入到IWO薄膜.实验获得的具有SiO2阻挡层的IWO薄膜的电子迁移率μ～54.5 cm2·V-1·s-1,电阻率p ～5.86×10-4Ω,cm,电子载流子浓度n～ 1.95×1020 cm-3,400～1600nm砌光谱区域内的平均透过率～76;.     

ZnO/SnO2复合透明导电膜性能的研究

采用直流磁控溅射工艺在SnO:透明导电玻璃上沉积一层ZnO膜,制备出ZnO/SnO2复合透明导电膜,作为硅薄膜太阳电池前电极.比较了具有不同ZnO厚度的复合膜氢轰击前后的光电性能,发现适当控制ZnO膜的厚度至关重要.研究了快速热退火(RTA)对薄膜的结构及光电性能的影响,发现400℃退火能够改善薄膜的光学性能.     

(C2N2H10)2Mg(HP2O7)2·2H2O synthesis and crystal structure

(C₂N₂H₁₀)₂Mg(HP₂O₇)₂·2H₂O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO₄(H₂O)₂] octahedra resulting in chains, which are linked via [HP₂O₇] units to form [Mg(HP₂O₇)₂(H₂O)₂]⁴⁻ layers. The Mg²⁺ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation.     

Crystal structure of Rb2[GeO2(OH)2]·2H2O

Single crystals of Rb₂[GeO₂(OH)₂] · 2H₂O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna2₁, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R ₁ = 0.0506. In [GeO₂(OH)₂]^2? anions, the Ge-O distances (1.71–1.73(1) Å) are shorter than the Ge-OH distances (1.76–1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed.     

Ultraviolet Absorption of Hg2Cl2-and Hg2Br2 Single Crystals

The optical unpolarized absorption spectra of Hg₂Cl₂ and Hg₂Br₂ single crystals were measured in the spectral range 230–400 nm. A sharp exciton peak and other absorption bands of both halides were observed near the fundamental absorption edge. The absorption peaks due to the splitting of the halogen doublet were also observed. Positions of the exciton peaks are characteristic for the Frenkel (localized) type of excitons. Possible interpretations of the other observed bands are discussed.     

Elastic properties of the dithionates Na2S2O6 · 2 H2O,K2S2O6, Rb2S2O6, CaS2O6 · 4H2O and SrS2O6 · 4 H2O

Single crystals of the title compounds having optical quality and dimensions of several cm were grown from aqueous solutions. The elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates. The true point symmetry of K₂S₂O₆ and Rb₂S₂O₆, which is screened by a hexagonal hypermorphy, could be clearly revealed to be trigonal (32) by the existence of the elastic constant c₁₄. In the case of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O the constant c₁₄ of the specimens appeared too small to confirm the trigonal symmetry group required from electrooptic and non-linear optic effects unambiguously. The isotypy of K₂S₂O₂ and Rb₂S₂O₆ as well as that of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O is confirmed by their elastic behaviour. The mean elastic stiffness of dithionates is closely related to that of the corresponding sulphates. In the vicinity of the second-order phase transition of K₂S₂O₆ near 235 K weak anomalies of the temperature derivatives of the longitudinal elastic stiffnesses are observed.     

Optical properties of the germanate melilites Sr2MgGe2O7, Sr2ZnGe2O7 and Ba2ZnGe2O7

Refractive indices and their dispersion in the wavelength range from 365 nm to 2325 nm and transmission ranges of the tetragonal melilite‐type germanates Sr₂MgGe₂O₇, Sr₂ZnGe₂O₇ and Ba₂ZnGe₂O₇ were determined. The uniaxial positive crystals Sr₂MgGe₂O₇ and Ba₂ZnGe₂O₇ both offer the possibility for phase matched second harmonic generation, a detailed analysis of phase matching conditions is given. The refractive indices of Sr₂ZnGe₂O₇ show an isoindex (isotropic) point at 467 nm. The investigation was performed on Czochralski grown large single crystals. The crystal structure of all three germanates were determined by means of X ‐ray diffraction. The results corroborate unmodulated melilite‐type structures at room temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure of bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate, [C6H5CH2CHCH2CH2NH2CH2CH2]2HPO4·5H2O

The salt bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate is orthorhombic with the following unit cell dimensions: a = 11.235(2) Å, b = 27.924(6) Å, c = 9.321(4) Å space group Pca2₁ with Z = 4. The structure was solved by the Patterson method and refined to final R value of 0.049 for 1802 independent reflections. The flack parameter is 0.14 with an e.s.d. of 0.23. The structure consists of infinite parallel two-dimensional [110] planes built of mutually connected ions and water molecules by strong O—H,...,O and N—H,...,O hydrogen bonding. There are no contacts other than normal van der Waals interactions between the layers.     

Optical Properties of MnIn2S2Se2 Single Crystals

Optical transmittance and reflectance spectra of MnIn₂S₂Se₂ single crystals are measured in the wavelength range from 0.5 to 30 μm. The interference method is used to determine the refractive index of the compound for wavelengths between 0.8 and 12 μm. From an analysis of the absorption spectrum it follows that the fundamental edge is due to forbidden indirect transitions between parabolic bands for the polarization E ⊥ c with a gap energy of 1.50 eV at room temperature.     

Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2

Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family A^I ₂B^II ₃(P₂O₇)₂; Ag₂Co₃(P₂O₇)₂ (I), Ag₂Mn₃(P₂O₇)₂ (II), and Na₂Cd₃(P₂O₇)₂ (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, = 80.83(6) = 81.45(4), = 72.87(5)°, V = 528.9(6) ų, Z = 2, D _calc = 4.649 mg/m³, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, = 80.78(8) = 82.43(9), = 72.82(7)°, V = 557.7(13) ų, Z = 2, D _calc = 4.338 mg/m³, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, = 77.0(2), = 82.5(2), = 67.8(2)°, V = 286(3) ų, Z = 2, D _calc = 4.249 mg/m³, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P₂O₇ groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.     

Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O 9 + : Synthesis and properties

Polycrystalline samples in the ternary system La₂Mo₂O₉-Sm₂W₂O₉-Sm₂Mo₂O ₉ ⁺ were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La₂Mo₂O₉) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases α → β and the appearance of the transition β _ms → β between two cubic phases. In samples with a high samarium content, the phase transition β _ms → β manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La₂Mo₂O₉.     

Synthesis and characterization of (NH4)2CuBr2Cl2·2H2O crystals

Single crystals of a new compound, (NH₄)₂CuBr₂Cl₂.2H₂O, were grown from saturated aqueous solution at room temperature by slow evaporation method. The grown crystals were characterized through elemental, powder XRD, thermal and DSC analyses and FTIR and far IR spectra. The elemental analysis and the decomposition pattern formulated using the TG‐DTG studies confirm the stoichiometry of the compound. The crystallinity of the compound is confirmed from the powder XRD pattern. A preliminary single crystal X‐ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with a = 7.7466 Å, b = 7.783 Å and c = 8.1211 Å. The low temperature DSC shows thermal anomalies at –161.1, –156.5, –152.4, –145.2, –134, –18.5, and 1.4°C during the heating run and at –4.3, –54.8, –66.1, –90.6, –109.7 and –147.2 °C during the cooling run. The thermal hysterses indicate first order phase transitions in the title compound at these temperatures. The FTIR spectra were used to assign the characteristic vibrational frequencies due to NH₄⁺, CuX₄^2– ions and other chemical bonds. The effect of substitution of two bromine atoms on the phase transitions of a closely related crystal, diammonium tetrachloro cuprate dihydrate is also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)