Si表面上生长的ZnO薄膜的阴极射线荧光

几种不同温度下退火的用直流溅射法生长的ZnO／Si样品的阴极射线荧光(CL)光谱显示，当退火温度低于等于800℃时，随着退火温度的升高，薄膜的晶体质量得到了改善，这主要体现在390nm紫外带的发射强度与505nm绿带发射强度的相对比值迅速增加，同时也发生了绿带的红移以及窄化效应。但退火温度超过800℃时绿带就不再红移了，其峰值为525nm。当退火温度为950℃时，紫外带几乎消失，而只剩下绿带，且与纯硅酸锌样品的CL谱一致，掠入射X射线衍射测量表明，确有三角相三元化合物硅酸锌的产生。因此，从ZnO／Si异质结的质量来看，直流溅射法可能不适宜用于生长这样的异质结：因为当退火温度低于800℃且相差较大(如600℃)时，不能得到产生强ZnO紫外发光的晶体质量，而当退火温度接近或高于800℃时，虽然zn0晶体质量得到了改善从而紫外发光份额迅速增加，但同时也产生了新的三元化合物硅酸锌，将严重影响ZnO／Si异质结的电学输运特性。     

Preparation of Cu（In,Ga）Se2 Thin Film Solar Cells by Selenization of Metallic Precursors in an Ar Atmosphere

Cu（In, Ga）Se2 thin films are deposited on Mo-coated glass substrates by Se vapour selenization of sputtered metallic precursors in the atmosphere of Ar gas flow under a pressure of about 10 Pa. The in situ heat treatment of as-grown precursor leads to the formation of a better alloy. During selenization, the growth of CuInSe2 phase preferably proceeds through Se-poor phases as CuSe and InSe at relatively low substrate temperature of 250℃, due to the absence of In2Se3 at intermediate stage at low reactor pressure. Subsequently, the Cu（In,Ga）Se2 phase is produced by the reactive diffusion of CuInSe2 with a Se-poor GaSe phase at high temperature of up to 560℃. The final film exhibits smooth surface and large grain size. The absorber is used to fabricate a glass/Mo/Cu（In, Ga）Se2/CdS/ZnO cell with the total-area efficiency of about 7%. The low open-circuit voltage value of the cell fabricated should result from the nonuniform distribution of In and Ga in the absorber, due to the diffusion-controlled reaction during the phase formation. The films, as well as devices, are characterized.     

Nonlinear Shift of the Raman A1 Mode in Ga-Incorporated CuInSe2 Thin Films

Composition dependence of quaternary CuIn1-x GaxSe2 films on Ga content has been systematically investigated by Raman scattering. The dominant A1 mode shifts from 174cm^-1 for CuInSe2 to 185cm^-1 for CuGaSe2 in an approximately polynomial curve other than a linear curve, indicating existence of asymmetric distribution of Ga and In on a microscopic scale in films. With Ga content x 〉 0.3, the significantly broadening and intensity decrease of A1 modes suggest the degradation of crystalline quality of chalcopyrite phase. Additionally, the quenching of additional Raman band at 183cm^-1 for the Ga-rich films reveals that CuAu-ordered phase can coexist in nominal chalcopyrite CuInSe2 films but not in CuGaSe2, due to Ga inhibition effect.     

The effect of composition on structural and electronic properties in polycrystalline CuGaSe2 thin film

Polycrystalline CuGaSe2 thin films on Mo-coated soda-lime glass substrates have been synthesized by coevaporation process from Cu, Ga and Se sources. Structural and electrical properties of the as-grown CuGaSe2 films strongly depend on the film composition. Stoichiometric CuGaSe2 is fabricated, as indicated by x-ray diffraction spectroscope （XRD） and x-ray fluorescence （XRF）. A two-phase region is composed of CuGaSe2 and Cu2-xSe phases for Cu-rich films, and CuGaSe2 and CuGa3Se5 phases for Ga-rich films, respectively. Morphological properties are detected by scanning electron microscope （SEM） for various compositional films, the grain sizes of the CuGaSe2films decrease with the extent of deviation from stoichiometric composition. Raman spectroscopy of Cu-rich samples shows that there exist large Cu-Se particles on the film surface. The results from Hall effect measurements for typical samples indicate that CuGaSe2 films are always of p-type semiconductor from Cu-rich to Ga-rich. Stoichiometric CuGaSe2 films exhibit relatively large mobility than any other compositional films. Finally, polycrystalline CuGaSe2 thin film solar cell with a best conversion efficiency of 6.02% has been achieved under the standard air mass （AM）1.5 spectrum for 100mW/cm^2 at room temperature （aperture area, 0.24cm^2）. The open circuit voltage of the CuGaSe2 solar cells is close to770 mV.     

Structure and Connectivity Analysis of Financial Complex System Based on G-Causality Network

The recent financial crisis highlights the inherent weaknesses of the financial market. To explore the mechanism that maintains the financial market as a system, we study the interactions of U.S. financial market from the network perspective. Applied with conditional Granger causality network analysis, network density, in-degree and out-degree rankings are important indicators to analyze the conditional causal relationships among financial agents, and further to assess the stability of U.S. financial systems. It is found that the topological structure of G-causality network in U.S. financial market changed in diferent stages over the last decade, especially during the recent global financial crisis. Network density of the G-causality model is much higher during the period of 2007–2009 crisis stage, and it reaches the peak value in 2008, the most turbulent time in the crisis. Ranked by in-degrees and out-degrees, insurance companies are listed in the top of 68 financial institutions during the crisis. They act as the hubs which are more easily influenced by other financial institutions and simultaneously influence others during the global financial disturbance.     

以硅为衬底的ZnO p-n结的制备及其结构、光学和电学特性

分别在n型半绝缘Si、弱n (n )以及强n (n+ )型Si片 (1 0 0 )面上用射频磁控反应溅射法和直流磁控反应溅射法制备了p型ZnO薄膜以及ZnO同质p n结。其中在生长p型ZnO时 ,反应室中通以过量的氧。对上述p型和n型ZnO薄膜进行了X射线衍射测量 ,在 34.1°附近得到了 0 .3°左右半峰全宽的ZnO(0 0 2 )衍射峰。ZnO薄膜的原子力显微镜图像上可见六角型的自组装结构。阴极射线荧光的测量显示了位于 390nm的紫外特征峰。用I V特性仪测量了上述ZnOp n结原型器件的I V电学输运曲线 ,其正向显示了约为 1 .1V的阈值 ,与日美科研人员用直流溅射和扩散法制备的ZnOp n结相似 ,但反向特性明显优于他们的     

Composition-induced structural modifications in the quaternary CuIn1-xGaxSe2 thin films： bond properties versus Ga content

In this paper the dependence of structural properties of the quaternary CuIn1-xGaxSe2 films with tetragonal structure on the Ga content has been systematically investigated by Raman scattering and x-ray diffraction spectra. The shift of the dominant A1 mode, unlike the lattice constants, does not follow the linear Vegard law with increasing Ga content x, whereas exhibits approximately polynomial change from 174 cm^-1 for CuInSe2 to 185 cm^-1 for CuGaSe2. Such behaviour should be indicative of presence of the asymmetric distribution of Ga and In on a microscopic scale in the films, due to Ga addition. The changes in the tetragonal distortion η lead to a significant variation in the anion displacement parameter U, which should be responsible for the evolution of bond parameters and resultant Raman bands with x.