Electronic properties and deep level transient spectroscopy of CdS/CdTe thin film solar cells

It is well known that preparing temperatures and defects are highly related to deep-level impurities. In our studies, the CdTe polycrystalline films have been prepared at various temperatures by close spaced sublimation (CSS). The different preparing temperature effects on CdS/CdTe solar cells and deep-level impurities have been investigated by I--V and C--V measurements and deep level transient spectroscopy (DLTS). By comparison, less dark saturated current density, higher carrier concentration, and better photovoltaic performance are demonstrated in a 580oC sample. Also there is less deep-level impurity recombination, because the lower hole trap concentration is present in this sample. In addition, three deep levels, E_v+0.341 eV(H4), E_v+0.226 eV(H5) and E_C-0.147 eV(E3), are found in the 580oC sample, and the possible source of deep levels is analysed and discussed.     

High-resolution transmission electron microscopy and bulk magnetometry study of LaFe11.5Si1.5 compound

This paper studies the microstructural and magnetic properties of LaFe11.5Si1.5 compound by means of high-resolution transmission electron microscope and bulk magnetometry measurements. The crystalline structure is accompanied with the noncrystalline and nanocrystalline structures. This characteristic is the reflection of the crystalline process held by quenching. The inverse susceptibilities diverge and deviate from Curie-Weiss law under low applied magnetic fields. This paper proposes the possible mechanism between the anomalous susceptibilities and microstructure, and offers a perspective on the magnetic properties of metastable intermetallic compounds.     

Capacitance characteristics of metal-oxide-semiconductor capacitors with a single layer of embedded nickel nanoparticles for the application of nonvolatile memory

This paper reports that metal-oxide-semiconductor (MOS) capacitors with a single layer of Ni nanoparticles were successfully fabricated by using electron-beam evaporation and rapid thermal annealing for application to nonvolatile memory. Experimental scanning electron microscopy images showed that Ni nanoparticles of about 5~nm in diameter were clearly embedded in the SiO₂ layer on p-type Si (100). Capacitance--voltage measurements of the MOS capacitor show large flat-band voltage shifts of 1.8~V, which indicate the presence of charge storage in the nickel nanoparticles. In addition, the charge-retention characteristics of MOS capacitors with Ni nanoparticles were investigated by using capacitance--time measurements. The results showed that there was a decay of the capacitance embedded with Ni nanoparticles for an electron charge after 10$^{4}$~s. But only a slight decay of the capacitance originating from hole charging was observed. The present results indicate that this technique is promising for the efficient formation or insertion of metal nanoparticles inside MOS structures.     

MCNP-FISPACT耦合燃耗计算程序开发与测试

反应堆堆芯的燃耗计算关系到堆芯的燃料管理,并直接影响堆芯的经济性评估,因此如何快速且准确地对堆芯进行燃耗计算一直是反应堆物理设计的研究重点之一。随着反应堆的发展,其几何结构和物理特性日渐复杂,现有的一维、二维耦合燃耗程序因其在几何处理上的限制,难以满足先进反应堆精细设计分析的要求。为对复杂反应堆堆芯的燃耗情况进行计算,结合粒子输运程序MCNP 处理复杂几何和燃耗程序FISPACT处理核素全面的特点,开发了接口程序耦合MCNP 和FISPACT来进行燃耗计算,并对耦合程序进行了计算验证。采用了IAEA 基准校核例题和CFETR中国聚变工程实验堆例题进行程序验证,经计算得出的有效倍增因子随燃耗的变化曲线和TBR等数据与标准例题的结果符合良好,其误差在可接受范围内。     

微观组织结构对铂钴永磁合金磁性能的影响

系统研究了Pt-Co合金磁性能与其微观组织结构间的关系.合金铸锭的X射线衍射结果表明：熔炼后的Pt-Co合金铸锭沿冷却方向存在明显的织构;扫描电镜照片显示合金的组织结构为柱状晶结构,柱状晶的生长方向平行于冷却方向;合金铸锭经塑性变形和再结晶处理后柱状晶组织消失,电镜照片显示处理后的合金晶粒尺寸变小且均匀;对不同组织结构的Pt-Co合金磁性能的测试结果表明,经塑性变形及再结晶处理后合金的磁性能有了明显提高,说明该合金中晶粒尺寸和取向是影响其矫顽力的重要因素. 关键词： 铂钴永磁合金 磁性能 织构     

CdSyTe1-y多晶薄膜的制备及光谱表征

采用真空共蒸发法制备了CdSyTe1-y(0≤y≤1)多晶薄膜,并用X射线衍射谱(XRD)、能量色散谱(EDS)研究了CdSyTe1-y多晶薄膜的结构、组分。实验结果表明:石英振荡法监控的组分与EDS谱结果较为一致;当y<0·3时,CdSyTe1-y多晶薄膜为立方结构,当y≥0·3时,CdSyTe1-y多晶薄膜为六方结构。采用XRD线形分析法可计算出CdSyTe1-y多晶薄膜晶粒大小约20～50nm。最后,用紫外-可见-近红外谱(UV-Vis-NIR),测得300～2500nmCdSyTe1-y多晶薄膜的透过率曲线,并结合一阶Sellmeier模型的折射率色散关系,表征了CdSyTe1-y多晶薄膜的光学性质,获得了CdS0·22Te0·78多晶薄膜的光学厚度d～535nm,光能隙Eg～1·41eV,以及吸收系数α(λ)、折射率n(λ)等光学量。结果也表明,采用真空共蒸发法可以制备需要组分的CdSyTe1-y多晶薄膜,对CdSyTe1-y多晶薄膜光学性质的表征方法可推广到其他的半导体薄膜材料。     

Effective anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent magnetic material

The effect of exchange-coupling interaction on the effective anisotropy and its varying tendency in nanocrystalline single-phase NdFeB permanent magnetic material have been investigated. The results show that the exchange-coupling interaction between grains makes the effective anisotropy of material, Keff, decrease with the reduction of grain size. The variation of Keff is basically the same as that of coercivity. The decrease in effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline single-phase NdFeB permanent magnetic material. In order to get high anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent material, the grain size should be larger than 35 nm.     

Fracture in sintered Sm−Co permanent magnetic materials

The bending strength and fracture toughness of sintered Sm-Co permanent magnetic materials are measured. A scanning electron microscope equipped with an energy dispersive X-ray analysis system is employed to investigate the bending fractography. The fracture behavior and micromechanism are discussed. The fracture behavior of sintered Sm-Co permanent magnetic materials exhibits cleavage fracture. Some Sm-rich impurities are found in fracture plane, suggesting that the Sm-rich impurities help reduce the cleavage brittleness of sintered Sm-Co permanent magnetic materials. The possible methods for improving the strength and toughness are also proposed.     

用光电子能谱研究CdTe太阳电池的背接触特性

CdTe太阳电池的背电极须采用高功函数金属。通过采用光电子能谱(XPS)分析了高功函数金属Au和Ni分别作为背电极的CdTe太阳电池背接触特性,发现在背电极剥离后,Au在ZnTe/ZnTe∶Cu背接触层表面以Au单质形式存在,扩散深度较浅;Ni扩散到ZnTe/ZnTe∶Cu复合层的深度比Au大,且大多呈离子态,与ZnTe/ZnTe∶Cu复合层中的富Te离子形成Ni_xTe,提高了掺杂浓度,使电池性能获得改善。在两样品中还发现,不论是Te的峰还是Zn的峰,其峰的位移变化都很小,说明两样品中Te和Zn的存在形式没有发生变化。     

非平行通光面激光变频器

当光通过一个光学器件时,一种减少两通光面反射损耗的方法,是将此两通光面切割成所谓的布儒斯特角且相互平行.这种相互平行的具有布儒斯特角通光面的光学器件,被用来减少反射损耗已经很多年了.激光发明以后,特别是二次谐波发生实现以后,上述这种平行式布儒斯特角切割方法,也曾不断用来降低倍频器的反射损失.但并没有人谈到过实验结果:这种将倍频器的通光面切割成相互平行的具有布儒斯特角的方法,是否真能减少倍频器的反射损耗?我们的回答是:不能.本文将从理论上说明为什么不能,并给出我们认为正确的切割方法.