SiC埋层的制备及其红外吸收特性

采用metal vapor vacuum arc离子源的离子束合成方法，对单晶Si衬底注入C^＋离子，获得不同剂量下的SiC埋层．C^＋离子束的引出电压为50kV，注入的剂量为3.0×10¹⁷—1.6×10¹⁸cm^-2．通过红外吸收谱的测试和分析，表明SiC埋层的结晶程度依赖于剂量的大小．研究证实，可以在较低的平均衬底温度下（低于400℃）得到含立方相结构的SiC埋层． 关键词：     

微波等离子体化学气相沉积方法在Si衬底上生长SiC纳米线

应用微波等离子体化学气相沉积方法,在单晶Si(100)衬底上生长出SiC纳米线.应用扫描电子显微镜、透射电子显微镜、能量损失谱(EDS)和选区电子衍射(SAD)等方法对纳米线化学组成和结构进行了分析和表征.给出该纳米线的生长机理 关键词： 微波等离子体化学气相沉积 SiC纳米线 生长机理     

Si衬底上异质外延金刚石的初始阶段原子H的作用及其界面结构

用高分辨率电子能量损失谱方法研究了原子H与被C₂H₂吸附的Si(100)界面的相互作用.结果显示,在Si(100)界面上,Si—Si二聚化键和C₂H₂中的C—C键被H原子打开,它们分别形成Si—H,C—H键.用AM1量子化学方法,计算了C₂H₂和C₂H₄在Si(100)上的吸附结构,指出了C₂H_{2关键词：}     

离子注入形成SOI结构的界面及埋层的俄歇能谱研究

本文中研究了O⁺(200keV,1.8×10¹⁸/cm²)和N⁺(190keV,1.8×10¹⁸/cm²)注入Si形成SOI(Silicon on Insulator)结构的界面及埋层的化学组成。俄歇能谱的测量和研究结果表明:注O⁺的SOI结构在经1300℃,5h退火后,其表层Si和氧化硅埋层的界面存在一个不饱和氧化硅状态,氧化硅埋层是由SiO₂相和这不饱和氧化硅态组成,而且氧化硅埋层和体硅界面不同于表层Si和氧化硅埋层界面;注N⁺的SOI结构在经1200℃,2h退火后,其氮化硅埋层中存在一个富N的疏松夹层,表层Si和氮化硅埋层界面与氮化硅埋层和体硅界面性质亦不同。这些结果与红外吸收和透射电子显微镜及离子背散射谱的分析结果相一致。还对两种SOI结构界面与埋层的不同特征的原因进行了分析讨论。 关键词：     

离子束合成钇硅化物的结构及红外谱特征

将稀土金属钇离子注入到n型单晶Si(111)中制备出钇硅化物埋层.利用x射线衍射、卢瑟福背散射和傅里叶红外吸收谱测量分析了样品的结构、原子的埋层分布和振动模式.结果表明，Y离子在注入过程中已与基底中的Si原子形成了YSi2结构相.真空下的红外光辐照处理促使YSi2择优取向生长，埋层中Si与Y的平均原子浓度比由24下降为20，与六方YSi2的化学计量比一致.还给出了钇硅化物的特征红外吸收谱.     

在p型硅MOS结构Si/SiO2界面区中与金有关的界面态和深能级

用深能级瞬态谱(DLTS)技术详细研究了金在p型<111>晶向硅MOS结构Si/SiO₂界面区中的行为。结果表明,金与Si/SiO₂界面缺陷H_it(0.494)相互作用形成新的缺陷Au-H_it(0.445),和金在硅的禁带中产生一个能量分布很广的连续界面态,利用这些界面态可以合理地解释金使硅MOS结构平带电压向正方向移动的物理机制。结果还表明,在Si/SiO₂界面附近的半导体中,金施主中心的剖面分 关键词：     

SiC外延层表面化学态的研究

用高分辨X射线光电子能谱仪(XPS)和傅里叶变换红外(FTIR)光谱仪研究了SiC外延层表面的组分结构. XPS宽扫描谱,红外掠反射吸收谱及红外镜面反射谱的解析结果说明SiC外延层表面是由Si—O—Si和Si—CH₂—Si聚合体构成的非晶SiC_xO_y:H. SiC外延层表面的化学态结构为Si(CH₂)₄,SiO(CH₂)₃,SiO₂(CH₃)₂,SiO₃(CH₃),Si—Si,游离H₂O,缔合OH,Si—OH,O和O₂. 根据化学态结构和元素电负性确定了化学态的各原子芯电子束缚能顺序,并与XPS窄扫描谱拟合结果相对比,建立了化学态与其束缚能的对应关系,进而用Si(CH₂)₄的实际C 1s束缚能值进行校正,确定了各化学态的束缚能. 结果发现,除了SiC_xO_y(x=1,2,3,4,x+y=4)的Si 2p束缚能彼此不同外,其C 1s和O 1s彼此也不相同,其中SiO₂(CH₃)₂和SiO₃(CH₃)的C 1s束缚能与CH_m和C—O中C 1s的相近,对此从化学态结构,元素电负性和邻位效应进行了解释. 关键词： SiC 化学态 XPS FTIR     

离子注入Si损伤分布的光谱法多层分析

应用多层模型和最优化方法,由实验测得的离子注入Si的椭偏光谱以及单晶Si和离子注入非晶Si的光学常数,能分析离子注入Si的损伤分布。我们测量了2.1—4.6eV能量范围的椭偏光谱和光学常数,建立了多层计算模型和最优化方法。在模拟分析的基础上,计算了能量为40keV,剂量分别为4×10¹³和1.4×10¹⁴cm^-2的As⁺注入Si的损伤分布,并与背散射测量的结果比较。用多层模型和最优化方法也能从光谱分析其它物理量的分布,只要这些物理量对光学性质有显著的影响,并且在测量过程中不随光子能量而改变。 关键词：     

射频溅射法制备3C-SiC和4H-SiC薄膜

利用射频溅射法在Si衬底上制备了SiC薄膜，并利用x射线衍射（XRD）和红外（IR）吸收谱对薄膜的结构、成分及化学键合状态进行了分析.XRD结果表明，低温制备的SiC薄膜为非晶相，而在高温下（＞800℃），薄膜呈现4HSiC和3CSiC结晶相.IR谱显示，溅射制备薄膜的吸收特性主要为Si—C键的吸收.此外，还利用原子力显微镜对薄膜的表面形貌进行了研究，并研究了样品的场发射特性. 关键词： 射频溅射 SiC薄膜 结构 表面形貌 场发射     

MgB2各向异性光学性质的第一性原理研究

使用密度泛函第一性原理研究了超导体MgB₂单晶各向异性的光学性质.在描述光学性质的基本理论和计算方法的基础上,计算了MgB₂的光电导谱、反射谱以及电子能量损失谱,并通过MgB₂的各个原子分解态密度图对所得到的反射谱和损失谱的各个谱峰做了详尽地分析.从光电导谱上来看,x方向与z方向有着很大差别,而在反射谱与电子能量损失谱中,x方向与z方向的特征峰位置都是相互符合的.从光导谱来看,沿 关键词： 超导体 电子结构 光学性质     

Silicon carbide synthesis with energy pulses

Polycrystalline SiC layers were synthesized through nanosecond pulse heating of thin carbon films deposited on single-crystalline silicon wafers. The samples were submitted to electron beam irradiation (25 keV, 50 ns) at various current densities in vacuum (10^–4mbar) and to XeCl excimer laser pulses (308 nm, 15ns) in air. Rutherford backscattering spectrometry (RBS) showed that in the e-beam annealed samples mixing of the elements at the interface starts at current densities of about 1200 A/cm². The mixed layer thickness increases almost linearly with current density. From the RBS spectra a composition of the intermixed layers close to the SiC compound was deduced. Transmission electron microscopy (TEM) and electron diffraction studies clearly evidenced the formation of SiC polycrystals. Using the XeCl excimer laser, intermixing of the deposited C film with the Si substrate was observed after a single 0.3 J/cm² pulse. Further analysis evidenced the formation of SiC nanocrystals, embedded in a diamond film.     

Comparative analysis of characteristic electron energy loss spectra and inelastic scattering cross-section spectra of Fe

The inelastic electron scattering cross section spectra of Fe have been calculated based on experimental spectra of characteristic reflection electron energy loss as dependences of the product of the inelastic mean free path by the differential inelastic electron scattering cross section on the electron energy loss. It has been shown that the inelastic electron scattering cross-section spectra have certain advantages over the electron energy loss spectra in the analysis of the interaction of electrons with substance. The peaks of energy loss in the spectra of characteristic electron energy loss and inelastic electron scattering cross sections have been determined from the integral and differential spectra. It has been shown that the energy of the bulk plasmon is practically independent of the energy of primary electrons in the characteristic electron energy loss spectra and monotonically increases with increasing energy of primary electrons in the inelastic electron scattering cross-section spectra. The variation in the maximum energy of the inelastic electron scattering cross-section spectra is caused by the redistribution of intensities over the peaks of losses due to various excitations. The inelastic electron scattering cross-section spectra have been analyzed using the decomposition of the spectra into peaks of the energy loss. This method has been used for the quantitative estimation of the contributions from different energy loss processes to the inelastic electron scattering cross-section spectra of Fe and for the determination of the nature of the energy loss peaks.     

Surface electron accumulation in indium nitride layers grown by high pressure chemical vapor deposition

Surface termination and electronic properties of InN layers grown by high pressure chemical vapor deposition have been studied by high resolution electron energy loss spectroscopy (HREELS). HREEL spectra from InN after atomic hydrogen cleaning show N-H termination with no indium overlayer or droplets and indicate that the layer is N-polar. Broad conduction band plasmon excitations are observed centered at 3400 cm⁻¹ in HREEL spectra with 7 eV incident electron energy which shift to 3100 cm⁻¹ when the incident electron energies are 25 eV or greater. The shift of the plasmon excitations to lower energy when electrons with larger penetration depths are used is due to a higher charge density on the surface compared with the bulk, that is, a surface electron accumulation. These results indicate that surface electron accumulation on InN does not require excess indium or In-In bonds.     

Inelastic electron scattering observation using energy filtered transmission electron microscopy for silicon -- germanium nanostructures imaging

This paper presents a new technique using energy filtered TEM (EFTEM) for inelastic electron scattering contrast imaging of Germanium distribution in Si-SiGe nanostructures. Comparing electron energy loss spectra (EELS) obtained in both SiGe and Si single crystals, we found a spectrum area strongly sensitive to the presence of Ge in the range [50-100 eV]. In this energy loss window, EELS spectrum shows a smooth steeply shaped background strongly depending on Ge concentration. Germanium mapping inside SiGe can thus be performed through imaging of the EELS background slope variation, obtained by processing the ratio of two energy filtered TEM images, respectively, acquired at 90 and 60 eV. This technique gives contrasted images strongly similar to those obtained using STEM Z-contrast, but presenting some advantages: elastic interaction (diffraction) is eliminated, and contrast is insensitive to polycrystalline grains orientation or specimen thickness. Moreover, since the extracted signal is a spectral signature (inelastic energy loss) we demonstrate that it can be used for observation and quantification of Ge concentration depth profile of SiGe buried layers.     

ZnO压敏陶瓷介电损耗的温度谱研究

利用Novocontrol宽频介电谱仪在-100—20 ℃温度范围内测量了ZnO-Bi₂O₃系压敏陶瓷的介电频谱,其频率范围为10^-2—10⁶ Hz. 研究表明： ZnO压敏陶瓷特征损耗峰的活化能分别为0.26和0.36 eV,结合实验条件、理论计算结果及其他现象的分析排除了特征损耗峰源于阴极电子注入、夹层极化和偶极子转向极化的可能.热刺激电流（TSC）谱共出现三个峰,其中高温峰对应于TSC实验加压过程引入的热离子极化,而中温峰和低温峰对应于介电损耗峰. 在分析的基础上,提出了ZnO压敏陶瓷的特征损耗峰起源于耗尽层内本征缺陷的电子弛豫过程. 关键词： ZnO压敏陶瓷 本征缺陷 介电谱 热刺激电流     

Design of an end station for a high current ion implantation system

Single crystal silicon has been implanted with nitrogen and phosphorus ions at MeV energies to fluences between 10¹⁶ and 1.6 × 10¹⁸ ions/cm₂. Infrared transmission and reflection spectra in the range of 1.25 to 40 μm were measured for as-implanted samples and after various annealing treatments. Interference fringes were observed in the IR spectra which are produced by the interference of light which has been multiply reflected between the front surface and the buried layers. By detailed theoretical analyses of the interference fringe structure, we obtained refractive index profiles, which, under suitable interpretation, provide accurate measurements and several quantities of interest. These quantities are the range and straggling of the implanted ions, the depth of disordered layers, and the width of the order-disorder transition. Mechanisms for the refractive index changes which have been identified include amorphization of the implanted silicon, bulk compositional change in the buried layer, localized vibrational mode dispersion, and free electron dispersion. Experimental results and theoretical predictions are presented, demonstrating each of these mechanisms.     

Measurement and interpretation of the electron energy loss spectra of iron and its oxides

The characteristic electron energy loss spectra of high purity samples of iron and its oxides were measured using cpmbined electron microscopy and energy analysis. By comparing these with X-ray absorption spectra it was possible to identify the single electron excitation processes and to deduce the plasmon energy of the electrons in iron.     

Characteristic energy gain and loss,double ionization,and ionization loss events in Be and BeO secondary electron spectra

Two satellite peaks have been observed on the high energy side of the Be KVV Auger peak. The lower energy satellite is attributed to coupling of energy from bulk plasmon de-excitations with Auger electrons, and the higher energy event to Auger electrons ejected from Be atoms with doubly ionized K levels. Following oxidation, the ionization loss spectra of BeO were observed to have structure which is interpreted as being related to the density of unfilled electron states above the BeO valence band. In addition, the characteristic loss and the low energy (“true secondary”) spectra of Be and BeO were determined. Peaks in these spectra are discussed in terms of characteristic energies related to excited electron states in the solids.