In-situ HVEM Observations of Dislocation Processes during High Temperature Deformation of Silicon Crystals

The characteristics in the plastic deformation of silicon crystals are first reviewed. Such characteristics have been interpreted quantitatively on the basis of some models on the velocity and the multiplication of dislocations during deformation. The results of the in-situ observations of silicon crystals deformed at elevated temperatures in a HVEM are presented. The slowness and the smoothness in the dislocation motion, the dynamic pile-up as a general mode of the collective motion of dislocations, the formation processes of multiplication centers of dislocations observed during the deformation all support the validity of the models adopted. Dislocation dipoles and Lomer-Cottrell sessiles are observed not to act as strong obstacles which play important roles in the work hardening of the crystals.     

Untersuchungen zum Einfluß von Temperatur und Versetzungen auf die integralen Röntgenintensitäten von Si-Einkristallen

It is possible to determine the Debye-temperature from measurements of the absolute integral X-ray intensities of silicon single crystals. Debye-temperatures of 543 to 533 K were found for a dislocation-free silicon crystal for temperatures between 90 and 296 K. The effect of dislocations on the Debye-temperature in silicon was investigated for various temperatures.     

In-situ Observations on Dynamic Processes Associated with Stacking Faults and Deformation Twins in Silicon Crystals

Stacking faults and thin deformation twins are observed to develop during the in-situ deformation of silicon crystals at elevated temperatures in a HVEM. Both the nucleation and the motion of partial dislocations take place under the applied stress in the regions of the stress concentration. Twinning dislocations moving on twin boundaries are extremely flexible. The spontaneous nucleation of loops of twinning dislocation on twin boundaries is observed rather frequently. No pole mechanism is observed to be operating. Stacking faults and deformation twins interact with glide dislocations moving along the intersecting planes by various ways.     

4H碳化硅单晶中的位错

4H碳化硅(4H-SiC)单晶具有禁带宽度大、载流子迁移率高、热导率高和稳定性良好等优异特性,在高功率电力电子、射频/微波电子和量子信息等领域具有广阔的应用前景。经过多年的发展,6英寸(1英寸=2.54 cm)4H-SiC单晶衬底和同质外延薄膜已得到了产业化应用。然而,4H-SiC单晶中的总位错密度仍高达10³~10⁴ cm^-2,阻碍了4H-SiC单晶潜力的充分发挥。本文介绍了4H-SiC单晶中位错的主要类型,重点讲述4H-SiC单晶生长、衬底晶圆加工以及同质外延过程中位错的产生、转变和湮灭机理,并概述4H-SiC单晶中位错的表征方法,最后讲述了位错对4H-SiC单晶衬底和外延薄膜的性质,以及4H-SiC基功率器件性质的影响。     

单晶硅外延生长晶化硅薄膜的研究

采用P型单晶硅片为衬底,并经混合酸溶液腐蚀抛光、清洗后,利用射频磁控溅射镀膜系统在其表面制备非晶硅薄膜;再结合快速光热退火工艺,于N2气氛下480℃退火30 min,得到晶化硅薄膜;利用光学金相显微镜、XRD衍射仪和拉曼散射光谱(Raman)仪对单晶硅衬底和晶化硅薄膜进行结构和性能表征.研究了混合酸溶液对单晶硅表面腐蚀效果、籽晶诱导外延生长晶化硅薄膜的物相结构和薄膜带隙.结果表明:采用混合酸溶液腐蚀后得到表面平整、光滑的单晶硅衬底;非晶硅薄膜经过快速退火后受籽晶诱导生成晶化硅薄膜,其晶相沿单晶硅衬底取向择优生长;随着非晶硅薄膜厚度从80 nm增加到280 nm,晶化后硅薄膜的表面粗糙度逐渐减小,晶化率从90.0;逐渐降低到37.0;;晶粒尺寸从6.65 nm逐渐减小到1.71 nm;带隙从1.18 eV逐渐升高到1.52 eV.     

多晶Si薄膜表面金催化Si纳米线生长

以Au膜作为催化剂和大晶粒多晶Si薄膜为衬底,利用固-液-固生长机制,制备出直径在30～ 100 nm和长度为几百微米的高密度Si纳米线.实验研究了退火温度、生长时间和N2流量对Si纳米线生长的影响.结果表明,随着退火温度的升高,生长时间的延长和N2流量的增加,Si纳米线的长度和密度都显著增加.对不同生长时间下获得的Si纳米线样品进行了X射线衍射测量,结果显示随着生长时间的延长,多晶Si薄膜和表面的Au膜成分都在减少.光致发光谱则显示出弱的蓝光发射和强的红光发射特性,前者应是由非晶SiOx壳层中的氧空位发光中心引起,后者则应归因于Si纳米线芯部与非晶SiOx壳层之间界面区域附近中的Si =O双键态或非桥键氧缺陷中心.     

Double-crystal Topographic Investigation of the Shape of Silicon Wafers after Oxidation

The shape of silicon wafers plastically deformed by slip band production during an oxidation process is investigated with double-crystal topography. In dependence on the Burgers vector of the slip band dislocations the tilt of parts of the wafer, especially between crossed slip bands, is observed and the wafer is curved in general. A local quantitative determination of the radius of curvature is possible.     

The X-ray topographic investigation of defect distribution in dendritic silicon crystals along their cross section

Using the modified method of limited X-ray topographs the distribution of defects along the silicon dendritic thickness was investigated. It is found that there are two dislocation sources in the given crystals, one of which acts near the surface and generates the loop-shaped dislocations in the centre of the sample. The other source located in the interior parts of the crystal creates the edge defect pilings.     

非晶/微晶过渡区内材料性能及电池的研究

本文采用甚高频等离子增强化学气相沉积(VHF-PECVD)技术,通过调节硅烷浓度,获得了系列硅薄膜材料,并用拉曼散射光谱和X射线衍射光谱对材料的结构特性进行了测试分析,同时还使用原子力显微镜观察比较了薄膜的表面形貌。结果发现:在非晶/微晶过渡区内存在着一个光敏性较大的区域,这个区域内的材料晶化率为零,但是表面存在一些微小的晶粒;与拉曼散射光谱相比,X射线衍射光谱对微小的晶化更加敏感。以这部分材料作为太阳电池的本征层,在SnO2衬底上制备了p-i-n型太阳电池,电池的初始开路电压(Voc)达到了0.891V。     

Three-dimensional global analysis of thermal stress and dislocations in a silicon ingot during a unidirectional solidification process with a square crucible

A three-dimensional global model was used to obtain the solution of a thermal field within the entire furnace during a unidirectional solidification process of multicrystalline silicon with a square crucible. Then the thermal stress distribution in the silicon ingot was solved. Based on the solution of thermal stress, relaxation of stress and multiplication of dislocations were performed by using the Haasen–Alexander–Sumino model (HAS model). The influence of crucible constraint on stress levels and dislocations was investigated. It was found that the crucible constraint had significant influence on the thermal stresses and dislocations in the ingot. The results indicated that it is important to reduce the crucible constraint in order to relax thermal stresses and reduce dislocations in a silicon ingot during the solidification process.     

Study of the diffraction contrast of dislocations in X-ray topo-tomography: A computer simulation and image analysis

Oblique X-ray diffraction images of individual dislocations in the symmetric Laue geometry from a plane-parallel silicon plate have been calculated based on the Takagi-Taupin equations and analyzed. Computer simulation is used to develop a general mathematical model of the formation of oblique images which correspond to sample rotation around the diffraction vector h in X-ray topo-tomography. The results of numerical calculations and analysis of different oblique images of straight-line dislocations, where the dislocation line vector τ lies in a plane parallel to input surface of {111}Si plate with a diffraction vector h 〈220〉, are presented.     

以高性价比颗粒硅带为衬底多晶硅薄膜的二次引铝低温制备法

本文报道了在廉价的颗粒硅带上用PECVD法并两次引入铝的工艺制备多晶硅薄膜.第一次引入铝是为了去除薄膜上过多的杂质;第二次引入铝是为了实现低温诱导结晶.通过对薄膜样品的拉曼谱和X射线衍射(XRD)谱分析,我们认为金属低温诱导结晶成功与否跟诱导前薄膜的结构密切相关.采用该工艺成功地制备了结晶度92;左右、可应用于太阳能电池的高纯优质多晶硅薄膜.     

前驱体法制备氮氧化硅纳米线及其光学性能研究

在Ni催化剂的存在下,通过SiCl4的水解氨解反应并在1300℃氨气气氛中进行热氮化处理制得了无定形氮氧化硅纳米线.产物经X射线衍射(XRD)、热重-差示扫描量热(TG-DSC)、扫描电镜(SEM)、透射电镜(TEM)、能量色散谱(EDS)和选区电子衍射(SAED)等表征手段进行分析,结果表明纳米线为无定形结构,直径为100～150nm.在波长为220nm的光激发下,产物的光致发光光谱(PL)在563nm和289nm处分别出现了一个强的绿光发光峰和一个弱的紫光发光峰.对纳米线的生长机理进行分析,表明纳米线的生长遵循气-液-固(VLS)机制控制模式.     

无电镀沉积于硅衬底上铜纳米晶的场发射性能

采用无电镀沉积技术在经过机械抛光的单晶硅衬底上沉积了铜纳米晶.利用X射线衍射数据,估算出所沉积铜纳米晶的平均粒径大约为40nm.对120s无电镀沉积样品的场发射测试表明,该样品的开启场强为～5.5V/μm,在场强达到9.26V/μm时的场发射电流密度可达到62.5μA/cm2.对相应的沉积过程和场发射机理进行了分析.结果表明,无电镀沉积技术有可能成为制备具有较好场发射性能的金属/硅冷阴极的一种可供选择的方法.     

X-Ray Topographic Investigation of Dendritic Silicon Crystals

Using Lang and double-crystal X-ray topographic methods the dislocation structure of dendritic silicon crystals have been investigated. It is shown that the surface layers of these crystals have a more perfect structure than their bulk volume. The twin lamella is a dislocation-free formation and there are dislocation-free zones ∼ 1,5 mm in width in the volume of crystals.     

Radial Distribution Analysis of the Structural Disordering in Mechanically Treated Silicon Powder

The changes in structure brought about by energy-intensive planetary grinding of silicon were investigated. The interpretation of the RDF obtained by X-ray diffraction analysis lead to the conclusion that the mechanically treated silicon is in a partially crystalline state. The spatial arrangement of the Si atoms is disturbed in a radial distance around 0.47 nm. The diametral size of the preserved regions d < 0.94 nm exceeds almost twice the size of the unit cell of Si and is of the same range as the size of crystallites in the mechanically treated silicon powder.     

微波等离子体化学气相沉积制备SiCN结晶膜及SiCN微米棒阵列

本文采用微波等离子体化学气相沉积(MPCVD)系统,以CH4, H2, N2作为源气体,以Si棒作为Si源,在Si衬底上制备出了SiCN结晶及SiCN微米棒阵列.样品的形貌由场发射扫描电子显微镜(SEM)表征分析.用X射线光电子谱(XPS)、Raman散射谱及X射线衍射(XRD)对样品的键合状态及结构进行表征,结果表明,所得到的SiCN薄膜是一具有新的六方结构的三元化合物.     

Refined Structure of Langmuir Lysozyme Films on Single-Crystal Silicon Wafers According to X-Ray Reflectivity Data

Crystallography Reports - Thin lysozyme films on single-crystal silicon wafers have been studied by X-ray reflectivity. The films have been formed using the modified Langmuir–Schaefer method...     

X-ray interferometric investigations of structural distortions in silicon crystals as a result of diffusion

The influence of boron diffusion on the X-ray Moiré pattern is investigated by means of X-ray interferometry. It is shown that at low boron concentrations in silicon, the Moiré patterns indicate the non-dislocative character of arising stresses. At higher concentrations the dislocations arise. Basing on the obtained topogram, the maximum local stress is evaluated, which at boron concentration of 2.5 · 10¹⁹ at/cm³ is 1.05 · 10⁸ N/m².     

镁离子掺杂多孔硅的蓝光发射

用电化学方法对多孔硅薄膜进行了镁离子的化学掺杂.用荧光分光光度计分析了样品的光致发光特性,发现镁掺杂增强了多孔硅的蓝光发射,当镁离子浓度增大到0.002mol/L时,可使蓝光强度达到多孔硅红光强度的一半.红外吸收谱表明,掺镁多孔硅的表面形成较完整的Si-O-Si网络结构,分析结果认为,多孔硅的蓝光光激发主要发生在多孔硅的纳米硅粒中,光发射主要发生在多孔硅中包裹纳米硅SiOx层中的发光中心上,对实验结果进行了合理的解释.