Cu100-xZrx金属玻璃压缩率及压力感生晶化现象

 本文采用金刚石对顶压砧高压装置和高压X射线技术测定了两种金属玻璃线压缩率曲线；得到Cu₃₀Zr₇₀和Cu₂₅Zr₇₅的线压缩率分别为2.7×10^-3 GPa^-1和2.3×10^-3 GPa^-1，实验最高压力超过30 GPa。实验过程中首次观察到Cu-Zr金属玻璃在室温下加压发生晶化的现象。     

Semileptonic decays Bc→(ηc,J/Ψ)lv in the perturbative QCD approach

In this paper we study the semileptonic decays of B_c^-→(η_c,J/Ψ)l^-v_l. We first evaluate the B_c→(η_c,J/Ψ) transition form factors F₀(q²), F₊(q²), V(q²) and A_0,1,2(q²) by employing the pQCD factorization approach, and then we calculate the branching ratios for all considered semileptonic decays. Based on the numerical results and the phenomenological analysis, we find that: (a) the pQCD predictions for the values of the B_c→η_c and B_c→J/Ψ transition form factors agree well with those obtained by using other methods; (b) the pQCD predictions for the branching ratios of the considered decays are Br(B_c^-→η_c e^-v_e(μ^-v_μ)=(4.41_-1.09^+1.22)×10^-3, Br(B_c^-→η_cτ^-v_τ) =(1.37_-0.34^+0.37)×10^-3, Br(B_c^-→J/Ψ e^-v_e(μ^-v_μ)) =(10.03_-1.18^+1.33)×10^-3, and Br(B_c^-→J/Ψτ^-v_τ) =(2.92_-0.34^+0.40)×10^-3; and (c) we also define and calculate two ratios of the branching ratios R_ηc and R_J/Ψ, which will be tested by LHCb and the forthcoming Super-B experiments.     

凝聚炸药中超压爆轰的实验研究

 采用飞片碰撞技术，在TNT/RDX（40/60）炸药中获得了2.5倍于正常爆轰的最大超压值，得到了超压爆轰下爆轰产物物态方程p=Aρ^{k+A₁(p-p_J)}（p－爆压，单位GPa，ρ－密度，单位kg/m³，A=ρ_J/ρ^k_J，p_J=27.06 GPa，ρ_J=2.3×10³ kg/m³，k=2.77，A₁=2.7×10^-3 GPa^-1，下表J代表正常爆轰状态）。该方程还可以较好地描述超压爆轰产物的二次冲击状态。     

Pure annihilation type decays B0→Ds- K2+ and Bs→Da2 in perturbative QCD approach

We calculate the branching ratios of pure annihilation type decays B⁰→D_s^- K₂^*+ and B_s→Da₂ using the perturbative QCD approach based on k_T factorization. The branching ratios are predicted to be (60.6_{-16.5-10.4-2.1}^{+17.3+4.3+3.2} )× 10^-6 for B⁰→D_s^- K₂^*+, (1.1_-0.4-0.2-0.1^+0.4+0.1+0.1)×10^-6 for B_s→D⁰a₂⁰ and (2.3_-0.8-0.4-0.1^+0.8+0.2+0.1)×10^-6 for B_s→D^-a₂⁺. They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the Standard Model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments to test the accuracy of theory and search of new physics signal.     

高组份Al值的AlxGa1-x As和AlxGa1-x As/GaAs/AlxGa1-xAs/GaAs多层结构的MOCVD生长

用自制常压MOCVD系统,在半绝缘GaAs衬底上生长高Al组份Al_xGa_1-xAs（其x值达0.83）,和Al_xGa_1-xAs/GaAs/Al_xGa_1-xAs/GaAs多层结构,表面镜面光亮。生长层厚度从几十到十几μm可控,测试表明外延层晶格结构完整,x值调节范围宽,非有意掺杂低,高纯GaAs外延层载流子浓度n_300K=1.7×10¹⁵cm^-3,n_77K=1.4×10¹⁵cm^-3,迁移率μ_300K=5900cmcm²/V.S,μ_77K=55500cm²/V.S。用电子探针,俄歇能谱仪测不出非有意掺杂的杂质,各层间界面清晰平直。 对GaAs,AlGaAs生长层表面缺陷,衬底偏角生长温度及其它生长条件也进行了初步探讨。     

SiC1-xGex/SiC 异质结光电二极管特性的研究

使用二维器件模拟软件Medici, 对SiC_1-xGe_x/SiC异质结的光电特性进行了模拟.设计了N型重掺杂SiC层的厚度为1 μm, P型轻掺杂SiC_1-xGe_x层厚为0.4 μm, 二者之间形成突变异质结.在反向偏压3 V、光强度为 0.23 W/cm²的条件下, p-n+ SiC_0.8Ge_0.2/SiC和p-n+ SiC_0.7Ge_0.3/SiC敏感波长λ分别可以达到0.64 μm和0.7 μm, 光电流分别为7.765×10^－7 A/μm和7.438×10^－7 A/μm; 为了进一步提高SiC_1-xGe_x/SiC 异质结的光电流, 我们把p-n+两层结构改进为p-i-n三层结构.在同样的偏压、光照条件下, p-i-n SiC_0.8Ge_0.2/SiC和p-i-n SiC_0.7Ge_0.3/SiC的光电流分别达到1.6734×10－6 A/μm和1.844×10－6 A/μm.     

Thermal Expansion Anomaly of Tb2Fe14Cr3 Compound

We investigate the thermal expansion property of the Tb₂Fe₁₄Cr₃ compound by means of x-ray diffraction. The result shows that the Tb₂Fe₁₄Cr₃ compound has a hexagonal Th₂Ni₁₇-type structure. Negative thermalexpansion is found in the Tb₂Fe₁₄Cr₃ compound from 296 to 493K by x-ray dilatometry. The coefficient of the average thermal expansion is α=-2.82 × 10^-5K^-1. In the temperature range 493--692K, the coefficient of the average thermal expansion is α=1.59 × 10^-5K^-1. The physical mechanism of thermal expansion anomaly of the Tb₂Fe₁₄Cr₃ compound is discussed according to the temperature dependence of magnetization measured by a superconducting quantum interference device.     

Uncertainty study of DS-(D-)→γlν (l=e,μ) decays determined by wave function

Wave function is important for determining decay constants f_DS^- and f_D^-. Using the 5 types of D meson wave functions in the heavy quark limit, we studied the uncertainties of radiative pure-leptonic decays of D_S^-(D^-) mesons. The branching ratios are (1.025390—1.706812) × 10^-5 and (0.953498—1.576725) × 10^-6 for D_S^- and D^- decays, respectively, which are sensitive to the type of wave function.     

高山宇宙线荷电强子流强的负正比

在海拔3220米的实验室里,用磁谱仪动量予选装置和多板云室,对落在0.23m²面积上的单根荷电强子进行了观测.考虑到各种可能的修正以后,得出在10—20 GeV/c之间,荷电强子的负正比为:N^-/N⁺=0.53±0.05.当认为N⁺只包含有P和π⁺,N^-是π^-,而且N_π+/N_π-=1时,推算出N_π-/N_p=0.9±0.1.若π^-积分谱的形式为j（>p）=Kp^-r,估算出在5—20 GeV/c的动量范围,r（?）2.3.本文也对荷电强子的积分流强作了粗略的估计,其结果是:j_⊥^p+π（>12 GeV/c）=（7.4±0.7）×10^-5cm^-2·st^-1·s^-1.     

高压下FexN化合物的相分解

 本文研究了室温下压力对Fe_xN化合物相分解的影响。X射线衍射分析表明，高压促使氮原子从Fe_xN化合物的晶格中脱溶出来，引起相分解，形成母相与α-Fe。这种相分解现象随压力增大而加强。通过分析不同压力下母相Fe_xN与α-Fe的相对含量，研究了氮从Fe_xN中脱溶的动力学过程，并计算出激活体积。对于Fe₃N和Fe₄N化合物，其激活体积分别为2.24×10^-5 m³/mol和1.62×10^-5 m³/mol。本实验还指出，通过对Fe_xN化合物的高压处理以及适当条件下退火，可以获得Fe₁₆N₂化合物。     

Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review

Ultrathin silicon wafer technology is reviewed in terms of the semiconductor applications, critical challenges, and wafer pre-assembly and assembly process technologies and their underlying mechanisms. Mechanical backgrinding has been the standard process for wafer thinning in the semiconductor industry owing to its low cost and productivity. As the thickness requirement of wafers is reduced to below 100 μm, many challenges are being faced due to wafer/die bow, mechanical strength, wafer handling, total thickness variation (TTV), dicing, and packaging assembly. Various ultrathin wafer processing and assembly technologies have been developed to address these challenges. These include wafer carrier systems to handle ultrathin wafers; backgrinding subsurface damage and surface roughness reduction, and post-grinding treatment to increase wafer/die strength; improved wafer carrier flatness and backgrinding auto-TTV control to improve TTV; wafer dicing technologies to reduce die sidewall damage to increase die strength; and assembly methods for die pick-up, die transfer, die attachment, and wire bonding. Where applicable, current process issues and limitations, and future work needed are highlighted.     

单晶热释电探测器混合集成制造方法研究

在比较几种探测器集成制造方法的基础上,提出采用各向异性导电膜作为电信号互联的手段,实现热释电探测器与信号处理电路的混合集成,从而演示了一种兼容性良好的集成化多传感器制造方法.对单晶钽酸锂热释电探测器采取机械研磨减薄获得其薄膜,利用3M的5552R各向异性导电膜,实现了探测器与信号读出电路的互联.对探测器的测试表明:机械研磨减薄获得的钽酸锂薄膜表现出与晶体接近的热释电特性,探测器表现出良好的绝热性质和动态响应特性.     

Heterogeneous integration of InP HEMTs on quartz wafer using BCB bonding technology

Heterogeneous integrated InP high electron mobility transistors(HEMTs)on quartz wafers are fabricated successfully by using a reverse-grown InP epitaxial structure and benzocyclobutene(BCB)bonding technology.The channel of the new device is In_0.7Ga_0.3As,and the gate length is 100 nm.A maximum extrinsic transconductance gm,max of 855.5 mS/mm and a maximum drain current of 536.5 mA/mm are obtained.The current gain cutoff frequency is as high as 262 GHz and the maximum oscillation frequency reaches 288 GHz.In addition,a small signal equivalent circuit model of heterogeneous integration of InP HEMTs on quartz wafer is built to characterize device performance.     

III‐V/silicon photonics for on‐chip and intra‐chip optical interconnects

In this paper III‐V on silicon‐on‐insulator (SOI) heterogeneous integration is reviewed for the realization of near infrared light sources on a silicon waveguide platform, suitable for inter‐chip and intra‐chip optical interconnects. Two bonding technologies are used to realize the III‐V/SOI integration: one based on molecular wafer bonding and the other based on DVS‐BCB adhesive wafer bonding. The realization of micro‐disk lasers, Fabry‐Perot lasers, DFB lasers, DBR lasers and mode‐locked lasers on the III‐V/SOI material platform is discussed.     

直接键合InP-GaAs结构界面的特性研究

通过对直接键合InP-GaAs结构的红外吸收光谱分析以及断面扫描电子显微镜观察发现，样品制备过程中不均匀的外加压强导致InP-GaAs交界面局部出现了不连续过渡的空间层，实验上将熔融石蜡渗透并被填充到该空间层，利用其对3.509μm波长光的强烈吸收特性可表征 这种局部的键合不连续区域，二维扫描测试样品不同区域的吸收谱得到3.509μm波长吸收强 度等值线图，从而描绘出外加压强的不均匀分布.实验上通过改进键合装置的施压均匀性， 得到了连续过渡界面且均匀键合的InP-GaAs结构，利用这种均匀键合技术有望制备大尺寸器 件例如光学微腔等. 关键词： 晶片直接键合 界面 红外吸收光谱     

High-density-plasma (HDP)-CVD oxide to thermal oxide wafer bonding for strained silicon layer transfer applications

Direct wafer bonding between high-density-plasma chemical vapour deposited (HDP-CVD) oxide and thermal oxide (TO) has been investigated. HDP-CVD oxides, about 230 nm in thickness, were deposited on Si(0 0 1) control wafers and the wafers of interest that contain a thin strained silicon (sSi) layer on a so-called virtual substrate that is composed of relaxed SiGe (∼4 μm thick) on Si(0 0 1) wafers. The surfaces of the as-deposited HDP-CVD oxides on the Si control wafers were smooth with a root-mean-square (RMS) roughness of <1 nm, which is sufficiently smooth for direct wafer bonding. The surfaces of the sSi/SiGe/Si(0 0 1) substrates show an RMS roughness of >2 nm. After HDP-CVD oxide deposition on the sSi/SiGe/Si substrates, the RMS roughness of the oxide surfaces was also found to be the same, i.e., >2 nm. To use these wafers for direct bonding the RMS roughness had to be reduced below 1 nm, which was carried out using a chemo-mechanical polishing (CMP) step. After bonding the HDP-CVD oxides to thermally oxidized handle wafers, the bonded interfaces were mostly bubble- and void-free for the silicon control and the sSi/SiGe/Si(0 0 1) wafers. The bonded wafer pairs were then annealed at higher temperatures up to 800 °C and the bonded interfaces were still found to be almost bubble- and void-free. Thus, HDP-CVD oxide is quite suitable for direct wafer bonding and layer transfer of ultrathin sSi layers on oxidized Si wafers for the fabrication of novel sSOI substrates.     

In situ surface topography measurement method of granite base in scanning wafer stage with laser interferometer

Topography of a granite surface has an effect on the vertical positioning of a wafer stage in a lithographic tool, when the wafer stage moves on the granite. The inaccurate measurement of the topography results in a bad leveling and focusing performance. In this paper, an in situ method to measure the topography of a granite surface with high accuracy is present. In this method, a high-order polynomial is set up to express the topography of the granite surface. Two double-frequency laser interferometers are used to measure the tilts of the wafer stage in the X- and Y-directions. From the sampling tilts information, the coefficients of the high-order polynomial can be obtained by a special algorithm. Experiment results shows that the measurement reproducibility of the method is better than 10 nm.     

调制激光致硅晶圆载流子辐射扫描成像试验研究

建立了调制激光诱发硅晶圆少数载流子密度波一维模型, 仿真分析了少数载流子输运参数对调制激光诱发载流子辐射信号频域响应的影响. 利用调制激光诱发载流子辐射扫描成像系统对含有表面划痕的硅晶圆进行了扫描成像试验研究. 通过少数载流子密度波模型与多参数拟合方法反求得到了扫描区域的输运参数二维分布图. 该方法得到的少数载流子寿命与利用传统光电导方法测量的少数载流子寿命结果相符; 分析了划痕对载流子输运参数造成的影响, 与光电导方法比较, 该方法可以测量不同位置的全部载流子输运参数且分辨率高.     

Characterization of si-GaAs wafer quality by room-temperature photoluminescence

The mapping of near-band-gap photoluminescence intensity is used as a method for characterizing the uniformity of wafer properties which is an essential requirement for fabrication of integrated circuits on si-GaAs substrates.

The surface effects on PL intensity and uniformity were investigated directly after an oxide removal etch and after storage of wafers under dark and illuminated conditions. Storage results in a decrease of the PL intensity and the PL contrast. This is probably associated with changes in the native oxide composition. PL changes during storage can be reversed by suitable oxide etching and cleaning which is important for obtaining reproducible results on wafer uniformity.

The bulk PL uniformity was studied in dependence on post-growth thermal treatments and distinct improvements in PL uniformity across a wafer were found due to various annealing conditions. Very low variations of < 10% are obtained by an optimized annealing process even up to 100 mm diameter wafers. High-resolution measurements show that these changes in wafer uniformity are correlated to characteristic microscopic changes within the well known cell structure.     

SiO2对多层GaN外延片热应力分布影响的仿真分析

为了研究SiO2对多层结构GaN外延片的热应力的影响,以直径d为40 mm的GaN外延片为研究对象,利用有限元分析法分别对蓝宝石/AlN/GaN和蓝宝石/SiO2/AlN/GaN这两种光阴极组件外延片表面热应力进行理论计算和仿真。在其他结构参数相同的情况下,分别分析了两种光阴极组件外延片径向和厚度方向的应力分布,分析了外延片热应力分布及影响因素。分析结果显示:在1 200 ℃的生长温度下,径向区域内的热应力分布比较均匀,厚度方向的热应力均在衬底和外延层的界面上发生突变。最后分析了外延片生长温度、蓝宝石衬底和GaN、AlN过渡层厚度对表面热应力的影响。