具有光电倍增的宽光谱三相体异质结有机彩色探测器

实验研究了P3HT：PBDT-TT-F：PCBM三相体异质结活性层光谱拓宽及其材料混合度对探测器光电特性的影响以及陷阱辅助光电倍增的机理.在此基础上,获得了一个覆盖350–750 nm波长范围的彩色探测器.该探测器在-1 V低偏压下红绿蓝三基色的光响应度和外量子效率分别达到了470,381,450 mA/W和93%,89%,121%,比探测率均接近10¹² Jones,且各基色的特性参数最大平均相对偏差均小于20%,同时频率带宽分别达到了5,8,8 kHz.结果表明：在保持二相体异质结薄膜原有微观形貌下,掺入少量光谱拓宽材料可实现活性层吸收光谱的拓宽.利用能级陷阱中电子的辅助作用引入外电路空穴注入,可实现探测器光电倍增.通过调节三相材料的混合度可实现基色间探测能力的均衡性.     

A comparative first-principles study of the adsorption of a carbon atom on copper and nickel surfaces

The adsorption energies of a carbon atom at the most stable adsorption sites on the Cu and Ni(100), (110) and (111) surfaces have been studied by first-principles calculations. The preference order of the adsorption sites for both Cu and Ni surfaces is the same. The (100) hollow site is the most stable one. The diffusion barriers for a C atom on the three surfaces have also been obtained, with the highest mobility on the (111) surface of both metals. Our investigation shows that the adsorption energies of the C atom on Ni are significantly higher in magnitude than those on Cu for all the three surfaces. This phenomenon is mainly due to the interaction and hybridization between C p-orbits and partially filed d-shell of Ni, which forms a stronger binding.     

Microstructure and tribological behavior of pulsed laser deposited a-CNx films

The a-CN_x films were deposited onto high-speed steel substrate by pulsed laser deposition at different nitrogen pressures. The tribological properties of the films in humid air and in vacuum were investigated using a ball-on-disk tribometer under various loads. The composition, microstructure and morphology of the films, wear tracks and paired balls were characterized by energy dispersive X-ray analysis (EDXA), X-ray photoelectron spectrum (XPS), Raman spectroscopy and scanning electron microscopy (SEM). With increasing the deposition pressure, the fraction of sp³ C bond reduces, the fraction of trapped nitrogen increases and the friction coefficient of the films declines both in humid air and vacuum. The friction coefficient of a-CN_x film decreases with increasing normal load. The tribological performances of the films in humid air are better than those of in vacuum. A transferred graphite-like tribo-layer is observed from a-CN_x film to the paired ball for both environments.     

H2O2–Ng dynamics predictions using an accurate potential energy surface

ABSTRACT

Based on ab initio calculations, our research group has built an analytical ground-state potential energy surface (PES) for hydrogen peroxide– noble gas (Ng) interactions, such as H₂O₂–He, H₂O₂–Ne, H₂O₂–Ar, H₂O₂–Kr, and H₂O₂–Xe complexes. From this PES, it was verified that the Ng presence does not affect the equilibrium values of the H₂O₂ dihedral angles. This happens because the H₂O₂ intramolecular barriers have much higher energies than the atom–bond interaction within these complexes. From this point of view, it is indeed reasonable to consider the H₂O₂ system as a rigid rotor, frozen at its equilibrium configuration. We present in this work the torsional motion for the H₂O₂ isolated system, the vibration–rotation energy levels and spectroscopic constants for hydrogen peroxide–noble gas by using the aforementioned PES. The predicted H₂O₂ torsional motions are in good agreement with both theoretical and experimental results available in the literature. Regarding H₂O₂–Ng ro-vibrational energies and spectroscopic constants, it is the first time that these calculations are presented in the literature. The current theoretical predictions are expected to be useful in the future experimental investigations.     

H3BO3对BaAl2Si2O8：Eu2+蓝色荧光粉物相组成和发光特性的影响

采用化学共沉淀法一次煅烧工艺合成了BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉.用X射线衍射仪、荧光分光光度计和扫描电镜测试了助熔剂H₃BO₃对BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉物相结构、发光性能、形貌等的影响.研究表明：化学共沉淀法一次煅烧工艺合成的BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉为单相,H₃BO₃的加入使基质结构由六方相转变成单斜相,并引起发射主峰位置和发射强度的变化;BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉的发光强度随着H₃BO₃加入量的增加先增强,后减弱,当加入H₃BO₃的质量分数为1.5%时,发光强度最大;H₃BO₃的加入使合成BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉的颗粒呈类球形,分布更加均匀,粒度更小. 关键词： 3BO₃')" href="#">H₃BO₃ 2Si₂O₈：Eu²⁺')" href="#">BaAl₂Si₂O₈：Eu²⁺ 发光特性 化学共沉淀法     

利用函数级数展开法求解Paul阱中射频源的倍频效应

采用函数级数展开法精确求解了在非理想射频源、考虑二次谐波Mathieu方程的解,得到了一些有意义的物理结果.     

二维颗粒气体在堆积过程中的能量耗散

通过高速摄像的方法观测了玻璃颗粒组成的准二维气态颗粒流的冷凝耗散过程,并和理想情况下的均匀耗散的颗粒流体理论作了比较,实验发现气态颗粒部分在耗散堆积过程中近似地满足高斯分布;从动能的结果来看,实际耗散过程和流体理论所预测的不同.实验发现冷凝分为两个阶段：当动能的贡献以气体颗粒为主时,发现颗粒以恒定的速度堆积,动能耗散主要由其中以气态分布的颗粒的沉积速率α,颗粒温度T和气态部分的平动速度ν_g决定;当气态颗粒数目趋向于0,能量耗散主要来自于密堆颗粒的表面层部分 关键词： 离散体系 耗散性     

Kinetics of oxygen exchange in strontium titanate

The kinetics of oxygen exchange are of primary importance for the application of titanates as fast resistive oxygen sensors. The sensor’s conductivity is correlated with the oxygen partial pressure pO₂ of the surrounding atmosphere: Due to oxygen surface transfer and subsequent diffusion of oxygen vacancies V _O ^·· , a pO₂ change gives rise to a conductivity change of the sample. While bulk diffusion usually occurs very fast, the surface transfer reaction becomes the rate determining step for thin samples and for low temperatures. We have shown that in the case of acceptor doped SrTiO₃ the kinetics of the surface transfer reaction can be strongly influenced through stoichiometric changes brought about by thin coatings of alkaline earth metal oxides (e.g. SrO). In contrast to the commonly used jump method (conductivity response to a sudden pO₂ change in the time domain), a model is presented which is based on the frequency-domain analysis of amplitude and phase shift of the response signal obtained from a pO₂ modulation in a fast kinetic measurement set-up. This method allows not only for measuring response times in the sub-millisecond range but also for distinguishing between behaviour either controlled by volume diffusion or by surface transfer reaction. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002.     

Growth atomic mechanisms of pulsed laser deposited La modified- $\mathsf{PbTiO_3}$ perovskites

The microstructure and morphology of 100/001-oriented La modified-PbTiO₃ (PLT) films grown by pulsed laser deposition have been analyzed and elucidated within the framework of morphology evolution models, such as the Dynamic Scaling Theory and Structure Zone Model. The experimental results were obtained from X-ray diffraction, atomic force microscopy and cross-section scanning electron microscopy. PLT grows with a compact columnar microstructure. The columns are formed by coherently grouped grains and show oblique walls and rounded tops. Connecting the experimental results with the morphology evolution models, the growth mechanisms involved in the deposition process were identified. While inside each column, the existing Pb vacancies govern the coarsening and coalescence of the grains, a non-local effect of geometric shadowing of the incident particle flux during growth controls competition between columns and their coarsening.Received: 18 June 2003, Published online: 22 September 2003PACS: 68.55.-a Thin film structure and morphology - 81.15.Fg Laser deposition - 77.84.Dy Niobates, titanates, tantalates, PZT ceramics, etc.E. Vasco: Current address: Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, GermanyC. Polop: Current address: I. Physikalisches Institut, RWTH-Aachen, 52056 Aachen, Germany