Annealing behaviors of photoluminescence from SiOx : H

The strong photoluminescence (PL) of SiOx:H prepared by plasma enhanced chemical vapor deposition has been systematically studied in conjunction with infrared and micro-Raman spectra. We have found that each PL spectrum is comprised of two Gaussian components, a main band and a shoulder. The main band might originate from amorphous silicon clusters embedded in die SiOx network, and its redshift with annealing temperature is due to expansion of the silicon clusters. The shoulder remains at about 835 nm in spite of the annealing temperature and possibly comes from luminescent defect centers. The enhanced PL spectra after 1170 degrees C annealing are attributed to the quantum confinement effects of nanocrystalline silicon embedded in the SiO2 matrix. (C) 1998 American Institute of Physics.

Nanostructure in the p-layer and its impacts on amorphous silicon solar cells

The open circuit voltage (V-oc) of n-i-p type hydrogenated amorphous silicon (a-Si:H) solar cells has been examined by means of experimental and numerical modeling. The i- and p-layer limitations on V-oc are separated and the emphasis is to identify the impact of different kinds of p-layers. Hydrogenated protocrystalline, nanocrystalline and microcrystalline silicon p-layers were prepared and characterized using Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), optical transmittance and activation energy of dark-conductivity. The n-i-p a-Si:H solar cells incorporated with these p-layers were comparatively investigated, which demonstrated a wide variation of V-oc from 1.042 V to 0.369 V, under identical i- and n-layer conditions. It is found that the nanocrystalline silicon (nc-Si:H) p-layer with a certain nanocrystalline volume fraction leads to a higher V-oc. The optimum p-layer material for n-i-p type a-Si:H solar cells is not found at the onset of the transition between the amorphous to mixed phases, nor is it associated with a microcrystalline material with a large grain size and a high volume fraction of crystalline phase. (c) 2006 Elsevier B.V. All rights reserved.

Photoluminescence and Raman scattering correlated study of boron-doped silicon nanowires

Boron-doped (B-doped) silicon nanowires (SiNWS) have been prepared and characterized by Raman scattering and photoluminescence (PL). B-doped SiNWS were grown by plasma enhanced chemical vapor deposition (PECVD), using diborane (B2H6) as the dopant gas. Raman spectra show a band at 480cm(-1),which is attributed to amorphous silicon. Photoluminescence at room temperature exhibits three distinct emission peaks at 1.34ev, 1.42ev, 1.47ev. Possible reason for these is suggested.

Comparative study of the surface passivation on crystalline silicon by silicon thin films with different structures

Si thin films with different structures were deposited by plasma enhanced chemical vapor deposition (PECVD), and characterized via Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The passivation effect of such different Si thin films on crystalline Si surface was investigated by minority carrier lifetime measurement via a method, called microwave photoconductive decay (mu PCD), for the application in HIT (heterojunction with intrinsic thin-layer) solar cells. The results show that amorphous silicon (a-Si:H) has a better passivation effect due to its relative higher H content, compared with microcrystalline (mu c-Si) silicon and nanocrystalline silicon (nc-Si). Further, it was found that H atoms in the form of Si-H bonds are more preferred than those in the form of Si-H-2 bonds to passivate the crystalline Si surface. (C) 2009 Elsevier B.V. All rights reserved.

稀土(III)及铜(II)、锌(II)有机磷（膦）酸酯配合物的晶体结构和振动光谱研究

本文包括标题配合物的结构和振动光谱两部分，共涉及了M(DMP)_n {n=2.3, M=2a, Nd, Cu. Zn}, Ln(DPP)_3{2n=2a-2u, Y}和Ln(BBP)_3 {Ln=La-Lu. Y}三类三十四个配合物。在结构方面，首次测定了Zn(DMP)_2和Cu(DMP)_2呈现出链状配位高聚结构，而La(DMP)_3, La(DMP)_3则为平面网状配位高聚结构。在Zn(DMP)_2, La(DMP)_3和Nd(DMP)_3中，配体以对称“O－P－O”桥键与金属原子配位，在相邻金属原子间形成双桥键。在Zn(DMP)_2中，每个Zn原子通过“O－P－O”双桥键与另两个Zn原子连接，Zn原子配位数为4，配位多面体为四面体构型；在La(DMP)_3和Nd(DMP)_3中，每个稀土原子通过“O－P－O”双桥键与另外三个稀土原子相连接，稀土原子的配位数为6，配位多面体LnO_6为八面体构型。在Cu(DMP)_3中， 配体以对称和非对称“O－P－O”桥键两种形式存在，其中非对称配位的配体形成为“Cu-O-P_O-Cu"-Cu，在铜原之间形成了一个单氧桥键。每个Cu原子通过双“O－P－O”桥键以及双单氧原子桥键与另外三个Cu原子相连接，Cu原子配位数为5，配位多面体为四角锥构型。在振动光谱方面，得到了上述配合物较为完整的光谱数据，并对主要光谱带进行了归属，如V_(M-O), V_(PO_2), V_(P-O(c)),VC-O, VP-C及σ_PO_2等。在稀土配合物中，稀土配位键的伸缩振动V_(vn-o)位于250cm~(-1)附近。V_(Cu)和V_(Zn-o)，在Cu(DMP)_2和Zn(DMP)_2中，分别为(412cm~(-1), 370cm~(-1))和(393cm~(-1), 386cm~(-1))。V_(as)PO_2和V_sPO_2，在配合物振动光谱中，分别在1130－1249cm~(-1)区和1084－1156cm~(-1)区。在稀土配合物中，VL_(n-o), V_(as)PO_2频率值，随镧系收缩逐渐递增。在Cu(DMP)_2红外谱中，非对称配体和对称配体的V_(as)PO_2和V_sPO_2, 分别为(1249cm~(-1)，1156cm~(-1))及(1177cm~(-1)，1090cm~(-1))，其劈裂值△V(V_(as)PO_2-V_sPO_2)为93cm~(-1)和87cm~(-1)。通过对配合物的常温和低温红外光谱的比较，确认了La(DMP)3和Nd(DMP)_3的176cm~(-1)、Ln(DPP)_3和Ln(BBP)_3的150cm~(-1)附近吸收为晶格振动。Ln(DPP)_3、Ln(BBP_3)的光谱性质与Ln(DMP)_3相似，我们认为它们之间具有相同的骨架结构－平面网状配位高聚结构。

MBE of GaN with DC-plasma source for nitrogen activation

In this paper we report on the first results of epitaxial growth of GaN layers on GaAs (100) substrates using a modified MBE system, equipped with a DC-plasma source for nitrogen activation in configuration of reverse magnetron at ultra-low pressures.

掺硼nc-Si:H薄膜中纳米硅晶粒的择优生长

利用等离子体增强化学气相沉积（PECVD）生长的系列掺硼氢化纳米硅（nc-Si:H）薄膜中纳米硅晶粒（nanocrystalline silicon，简称nc-Si)有择优生长的趋势。用HRTEM、XRD、Ramam等方法研究掺硼nc-Si:H薄膜的微观结构时发现：掺硼nc-Si:H薄膜的XRD只有一个峰，峰位在2θ≈47°，晶面指数为（220），属于金刚石结构。用自由能密度与序参量的关系结合实验参数分析掺硼nc-Si:H薄膜择优生长的原因是：适当的电场作用引起序参量改变，导致薄膜在适当的自由能范围内nc-Si的晶面择优生长。随着掺硼浓度的增加，nc-Si:H薄膜的晶态率降低并逐步非晶化。nc-Si随射频功率密度的增大而长大，但晶态率降低。nc-Si随衬底温度升高而长大，晶态率提高。nc-Si随射频功率密度的增大而长大，晶态率增大的趋势平缓。但未发现掺硼浓度、稀释比、衬底温度、射频功率密度的变化引起薄膜中nc-Si晶面的择优生长。

Raman scattering and infrared absorption of silicon nanocrystals in silicon oxide matrix

Structural dependence on annealing of a-SiOx:H was studied by using infrared absorption and Raman scattering. The appearance of Raman peaks in the range of 513-519cm(-1) after 1170 degreesC annealing was interpreted as the formation nanocrystalline silicon with the sizes from 3-10nm. The Raman spectra also show the existence of amorphous-like silicon phase, which is associated with Si-Si bond re-construction at boundaries of silicon nanocrystallites. The presence of the shoulder at 980cm(-1) of Si-O-Si stretching vibration at 1085cm(-1) in infrared spectra imply that except that SiO2 phase, there is silicon sub-oxide phase in the films annealed at 1170 degreesC. This sub-oxide phase is located at the interface between Si crystallites and SiO2, and thus support the shell model for the mixed structures of Si grains and SiO2 matrix.

The diphasic nc-Si/a-Si : H thin film with improved medium-range order

A series of silicon film samples were prepared by plasma enhanced chemical vapor deposition (PECVD) near the threshold from amorphous to nanocrystalline state by adjusting the plasma parameters and properly increasing the reactions between the hydrogen plasma and the growing surface. The microstucture of the films was studied by micro-Raman and Fourier transform infrared (FTIR) spectroscopy. The influences of the hydrogen dilution ratio of silane (R-H = [H-2]/[SiH4]) and the substrate temperature (T-s) on the microstructural and photoelectronic properties of silicon films were investigated in detail. With the increase of RH from 10 to 100, a notable improvement in the medium-range order (MRO) of the films was observed, and then the phase transition from amorphous to nanocrystalline phase occurred, which lead to the formation of diatomic hydrogen complex, H-2* and their congeries. With the increase of T-s from 150 to 275 degreesC, both the short-range order and the medium range order of the silicon films are obviously improved. The photoconductivity spectra and the light induced changes of the films show that the diphasic nc-Si/a-Si:H films with fine medium-range order present a broader light spectral response range in the longer wavelength and a lower degradation upon illumination than conventional a-Si:H films. (C) 2004 Elsevier B.V. All rights reserved.

Impact of wide bandgap p-type nc-Si on the performance of a-Si solar cells

This paper reports the impact of a wide bandgap p-type hydrogenated nanocrystalline silicon (nc-Si:H) on the performances of hydrogenated amorphous silicon (a-Si:H) based solar cells. The player consists of nanometer-sized Si crystallites and has a wide effective bandgap determined mainly by the quantum size-confinement effect (QSE). By incorporation of this p-layer into the devices we have obtained high performances of a-Si:H top solar cells with V-infinity=1.045 V and FF=70.3 %, and much improved mid and bottom a-SiGe:H cells, deposited on stainless steel (SS) substrate. The effects of the band-edge mismatch at the p/i-interface on the I-V characteristics of the solar cells arc discussed on the bases of the density-functional approach and the AMPS model.

The main factor influencing the tensile properties of surface nano-crystallized graded materials

The improved mechanical properties of surface nano-crystallized graded materials produced by surface severe plastic deformation ((SPD)-P-2) are generally owing to the effects of the refined structure, work-hardened region and compressive residual stress. However, during the (SPD)-P-2 process, residual stress is produced simultaneously with work-hardened region, the individual contribution of these two factors to the improved mechanical properties remains unclear. Numerical simulations are carried out in order to answer this question. It is found that work hardening predominates in improving the yield strength and the ultimate tensile strength of the surface nano-crystallized graded materials, while the influence of the residual stress mainly emerges at the initial stage of deformation and decreases the apparent elastic modulus of the surface nano-crystallized graded materials, which agrees well with the experimental results. (C) 2010 Elsevier B.V. All rights reserved.

纳米晶材料变形行为的微观力学分析

将纳米晶材料视为包括晶粒和晶界的两相复合材料.基于能量平衡概念推导出纳米晶材料的增量本构关系.最后将本文发展的模型用于纯铜的单轴拉伸实验,讨论了晶粒大小、形状和晶粒分布的影响,并将模型预测的结果和已有的实验结果进行比较.

分立元件的RF宽带放大电路研制

介绍一种由新研制的由分立元件组成的快放大器。该电路是一个交流耦合放大器,具有较高的电源增益(Av≥500),快的上升延(tr≤1.7ns),低噪声(等效到输入端噪声vn≤3μs),该放大器主要用于我所束流诊断系统中放大来自相位探针的微弱信号。