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211.
Effect of high-temperature buffer thickness on quality of AlN epilayer grown on sapphire substrate by metalorganic chemical vapor deposition 下载免费PDF全文
The effect of an initially grown high-temperature AlN buffer (HT-AlN) layer's thickness on the quality of an AlN epilayer grown on sapphire substrate by metalorganic chemical vapor deposition (MOCVD) in a two-step growth process is investigated. The characteristics of AlN epilayers are analyzed by using triple-axis crystal X-ray diffraction (XRD) and atomic force microscopy (AFM). It is shown that the crystal quality of the AlN epilayer is closely related to its correlation length. The correlation length is determined by the thickness of the initially grown HT-AlN buffer layer. We find that the optimal HT-AlN buffer thickness for obtaining a high-quality AlN epilayer grown on sapphire substrate is about 20 nm. 相似文献
212.
采用一种新型的电子传输材料TFTTP作为阴极缓冲层提高基于SubPc/C60异质结的有机薄膜太阳能电池的性能. 通过在有机活性层和金属电极之间加入TFTTP界面层,器件的能量转换效率提高了约30%. 系统研究了器件的二极管特性、光电流特性以及内部的光场分布情况,结果表明,TFTTP阴极缓冲层的引入可以有效地提高器件的内建电场,进而增加电荷转移激子的分离效率. 通过使用TFTTP作为阴极缓冲层,在C60/金属界面形成良好的欧姆接触,降低了界面接触电阻,有利于自由载流子的收集. 相似文献
213.
Organic solar cells with inverted planar heterojunction structure based on subphthalocya-nine and C60 were fabricated using several kinds of materials as cathode buffer layer (CBL), including tris-8-hydroxy-quinolinato aluminum (Alq3), bathophenanthroline (Bphen), bathocuproine, 2,3,8,9,14,15-hexakis-dodecyl-sulfanyl-5,6,11,12,17,18-hexaazatrinaphthylene (HATNA), and an inorganic compound of Cs2CO3. The influence of the lowest unoccupied molecular orbital level and the electron mobility of organic CBL on the solar cells perfor-mance was compared. The results showed that Alq3, Bphen, and HATNA could significantly improve the device performance. The highest efficiency was obtained from device with an-nealed HATNA as CBL and increased for more than 7 times compared with device without CBL. Furthermore, the simulation results with space charge-limited current theory indicated that the Schottky barrier at the organic/electrode interface in inverted OSC structure was reduced for 27% by inserting HATNA CBL. 相似文献
214.
Erbium, and erbium and ytterbium co-doped YVO4 waveguiding films were deposited on MgO/Si substrates by PLD. The samples were post-annealed at two different temperatures in air atmosphere. The influence on the crystalline structure and waveguiding properties of the films at these annealing temperatures for two dopant concentrations was investigated. Layers annealed up to 900 °C are polycrystalline. The dominant fraction of YVO4 crystallites exhibited preferred orientation of the (0 0 1) zone axes parallel to the substrate surface. The polycrystalline samples show difference in the refractive indexes Δn (Δn = nTE − nTM) for TE and TM polarizations. 相似文献
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216.
Atanu Mitra 《Tetrahedron letters》2009,50(7):776-1321
A new glucose-based C2-derivatized colorimetric chemo-sensor (L1) has been synthesized by a one-step condensation of glucosamine and 2-hydroxy-1-naphthaldehyde for the recognition of transition metal ions. Among the eleven metal ions studied, viz., Mg2+, Ca2+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+, L1 results in visual colour change only in the presence of Fe2+, Fe3+and Cu2+ in methanol. However, in an aqueous HEPES buffer (pH 7.2) it is only the Fe3+ that gives a distinct visual colour change even in the presence of other metal ions, up to a concentration of 280 ppb. The changes have been explained based on the complex formed, and the composition has been determined to be 2:1 between L1 and Fe3+ based on Job’s plot as well as ESI MS. The structure of the proposed complex has been derived based on HF/6-31G calculations. 相似文献
217.
Philip E. Mason Derek C. Schildt Timothy G. Strein 《Journal of chromatography. A》2009,1216(1):154-158
Previous work has demonstrated proof-of-concept for carrying out the clinically useful Jaffe reaction between creatinine and picrate within a capillary tube using electrophoretically mediated microanalysis (EMMA). Here, it is shown that careful control of reagent plug length as well as concentration and pH of the background electrolyte (BGE) can result in a marked improvement in the sensitivity of this assay. Increasing the length of the picrate reagent zone is shown to give rise to as much as a 3–4-fold enhancement, and increasing the concentration and/or pH of the borate buffer also results in an additional, albeit modest, improvement in sensitivity. Interestingly, borate BGE concentrations approaching 100 mM give rise to an unexplained drop in reaction efficiency, an effect which can be avoided by utilizing lower borate concentration with higher pH. The improvements appear to primarily minimize electrodispersion of the picrate reagent, allowing higher picrate concentration in the reaction zone. The same conditions also appear to minimize the electrodispersion of the in-line product as well. With optimized EMMA parameters, the sensitivity of the in-line Jaffe chemistry can be enhanced to an extent that there is no need for the two capillary “high sensitivity” detection system required in previous work. Using optimized conditions, three different human serum samples spanning the expected clinical range of creatinine concentrations were successfully analyzed. Overall, this work illustrates the importance of systematically characterizing the conditions under which EMMA analyses are carried out. 相似文献
218.
219.
采用溶胶凝胶旋涂法,在石英衬底上引入缓冲层制备ZnO∶Sn薄膜.利用四探针电阻率测试仪、X射线衍射仪(XRD)、光致发光(PL)谱仪、场发射扫描电子显微镜(FE-SEM)等测试手段对薄膜的微观结构和光电性能进行表征.结果表明:所制样品均呈现六角纤锌矿晶体结构并沿C轴择优生长,薄膜的结晶质量和光电性能达到改善,适当厚度的缓冲层可以有效缓解薄膜和衬底间的晶格失配.随着缓冲层厚度的增加,薄膜的电导率以及在可见光范围的透过率先增大后减小.制备两层缓冲层薄膜性能最优,电阻率达到9.5×10-3 Ω·cm,可见光波段的平均透过率为91;. 相似文献
220.