硼/氮原子共掺入金刚石的晶格损伤及其退火过程的计算机模拟

借助于Tersoff势函数和分子动力学模拟技术研究了室温下500eV的能量粒子硼(4个)和氮(8个)共掺入金刚石晶体中所引起的损伤区域内晶体微细观结构的变化特征以及后续加热退火晶体结构的演变特征.结果表明：随着掺入原子数目的增加，受影响的区域范围渐渐增大，12个粒子全部注入金刚石晶体后局部影响区域的半径达0.68nm，损伤区域中心的三配位原子数增加而四配位数原子数量减少.加热退火过程中损伤中心区域的原子发生扩散，部分原子的扩散距离达到4个晶格间距.加热退火使损伤区域中心原子间的平均键长趋于金刚石结构的键长.退火后薄膜中注入的杂质原子向表面扩散引起应力分布产生变化，杂质原子经过一系列的扩散过程能够到达空位的位置，减少薄膜中空位数量，减小晶格畸变程度，原子向表面扩散引起应力产生重新分布，薄膜中应力峰值的峰位向薄膜表面发生移动，局部应力集中程度降低.通过不同退火温度的比较发现低温下退火(800℃)更有利于空位的运动和晶格损伤的恢复从而提高晶格质量. 关键词： 金刚石共掺杂 分子动力学 退火     

退火温度对ZrO2纳米材料中Eu3+离子发光的影响

研究了退火温度对ZrO₂纳米材料中Eu³⁺离子发光性质的影响. 材料的结构、晶粒尺寸和形状以及晶格的排列分别由XRD，TEM表征. 结果表明：用共沉淀法制备的ZrO₂纳米材料具有不随退火温度变化、稳定的四方结构；材料的晶粒尺寸随退火温度的提高而增大；晶格的排列由无序逐渐变为有序；发射光谱表明其主要发射在595 nm和604 nm处；在394 nm的紫外光辐照下得到了不同样品的604 nm荧光发射强度的变化不同. 这种现象与样品中O^2-离子含量和样品表面的表面缺陷有关；另外，电荷迁移带随退火温度的变化而变化.     

模拟退火算法在波束图设计中的应用

摘要本文提出了基于模拟退火算法的波束设计方法。模拟退火算法模拟了固体缓慢退火从而获得最低内能的物理过程，是一种简单而有效的随机性全局优化算法。为证明该设计方法的可行性和有效性，给出了15元平面阵的设计实例以及仿真结果。结果表明，使用该方法设计的波束与常规方法相比，获得了更低的旁瓣级。     

一种基于OTF稳定性的波前编码相位板优化方法

提出了一种简单的可用于光学系统中子午弧矢方向白光OTF稳定性评价的波前编码相位板参量优化方法.该方法仅以标准偏差来评价OTF在目标景深范围内的稳定性,并且结合自适应模拟退火算法在参量空间内优化得到相位板的最佳参量.使用该方法优化得到的相位板参量,可以大幅度提高光学系统的景深,并且可以获得更为清晰、稳定的成像.对应用波前编码技术前后光学系统的成像性能作了比较,并且考察了优化参量的容差性.     

GeV能量的Fe离子在C60薄膜中的辐照效应研究

利用傅立叶转换红外光谱和Raman谱仪分析了0.98 GeV的Fe离子在电子能损Se为3.5 keV/nm时， 不同辐照剂量（5×1010 —8×1013 ions/cm2)下， 在C60薄膜中引起的辐照损伤效应。 分析表明， Fe离子辐照引起了C60分子的聚合与损伤。 在辐照剂量达到一中间值1×1012 ions/cm2， C60分子的损伤得到部分恢复， 归因于电子激发引起的退火效应。 通过对Raman数据的拟合分析， 演绎出Fe离子辐照在C60材料中形成的潜径迹截面或引起损伤的截面约为1.32×10-14 cm2。     

Fluctuation of semiconductor surface potential in Si-SiO<Subscript>2</Subscript> structure after irradiation and subsequent annealing

Fluctuations of the semiconductor surface potential in a Si-SiO₂ structure, caused by irradiation with different high-energy particles (50 MeV electrons and 40 keV arsenic ions) and subsequent annealing, have been studied by measuring the semiconductor interface state parameters. It is established that the fluctuation of the semiconductor surface potential decreases slightly, from 0.049 V to 0.044 V, after irradiation, while a considerable increase is observed after annealing. For the samples irradiated by arsenic ions, the increase in fluctuation is much larger (0.096 V) than that for the electron-irradiated samples (0.06 V).     

Excimer laser processing of ZnO thin films prepared by the sol-gel process

ZnO thin films were prepared on soda-lime glass from a single spin-coating deposition of a sol-gel prepared with anhydrous zinc acetate [Zn(C₂H₃O₂)₂], monoethanolamine [H₂NC₂H₄OH] and isopropanol. The deposited films were dried at 50 and 300 °C. X-ray analysis showed that the films were amorphous. Laser annealing was performed using an excimer laser. The laser pulse repetition rate was 25 Hz with a pulse energy of 5.9 mJ, giving a fluence of 225 mJ cm⁻² on the ZnO film. Typically, five laser pulses per unit area of the film were used. After laser processing, the hexagonal wurtzite phase of zinc oxide was observed from X-ray diffraction pattern analysis. The thin films had a transparency of greater than 70% in the visible region. The optical band-gap energy was 3.454 eV. Scanning electron microscopy and profilometry analysis highlighted the change in morphology that occurred as a result of laser processing. This comparative study shows that our sol-gel processing route differs significantly from ZnO sol-gel films prepared by conventional furnace annealing which requires temperatures above 450 °C for the formation of crystalline ZnO.     

Analysis of excimer laser annealing of amorphous SiGe on La2O3//Si structures

The reduction of complementary metal oxide semiconductor dimensions through transistor scaling is in part limited by the SiO₂ dielectric layer thickness. Among the materials evaluated as alternative gate dielectrics one of the leading candidate is La₂O₃ due to its high permittivity and thermodynamic stability. However, during device processing, thermal annealing can promote deleterious interactions between the silicon substrate and the high-k dielectric degrading the desired oxide insulating properties.The possibility to grow poly-SiGe on top of La₂O₃//Si by laser assisted techniques therefore seems to be very attractive. Low thermal budget techniques such as pulsed laser deposition and crystallization can be a good choice to reduce possible interface modifications due to their localized and limited thermal effect.In this work the laser annealing by ArF excimer laser irradiation of amorphous SiGe grown on La₂O₃//Si has been analysed theoretically by a numerical model based on the heat conduction differential equation with the aim to control possible modifications at the La₂O₃//Si interface. Simulations have been carried out using different laser energy densities (0.26-0.58 J/cm²), different La₂O₃ film thickness (5-20 nm) and a 50 nm, 30 nm thick amorphous SiGe layer. The temperature distributions have been studied in both the two films and substrate, the melting depth and interfaces temperature have been evaluated. The fluences ranges for which the interfaces start to melt have been calculated for the different configurations.Thermal profiles and interfaces melting point have shown to be sensitive to the thickness of the La₂O₃ film, the thicker the film the lower the temperature at Si interface.Good agreement between theoretical and preliminary experimental data has been found.According to our results the oxide degradation is not expected during the laser crystallization of amorphous Si_0.7Ge_0.3 for the examined ranges of film thickness and fluences.     

Hysteresis of ruby fluorescent line by pressure and annealing effect

Abstract

Accuracy of hydrostatic pressure measurement in a diamond-anvil cell (DAC) depends on the reproducibility of ruby RI fluorescent measurement. The larger scatter in R, fluorescent wavelength shift than the reproducibility of spectroscopic measurement was observed among appropriately mirror-finished ruby plates before setting up in DAC. The characteristics of the scatter changed after loading DAC up to pressure over hydrostatic limit. They vanished by annealing the ruby plates. These phenomena are presumably due to the appearance and disappearance of the residual stress in the ruby crystal. Such hysteresis of ruby fluorescent wavelength shift by pressure and its annealing effect are discussed.     

High performance semiconducting polymers containing bis(bithiophenyl dithienothiophene)‐based repeating groups for organic thin film transistors

New dithienothiophene‐containing conjugated polymers, such as poly(2,6‐bis(2‐thiophenyl‐3‐dodecylthiophene‐2‐yl)dithieno[3,2‐b;2′,3′‐d]thiophene, 4 and poly(2,6‐bis (2‐thiophenyl‐4‐dodecylthiophene‐2‐yl)dithieno[3,2‐b;2′,3′‐d]thiophene, 8 have been successfully synthesized via Stille coupling reactions using dodecyl‐substituted thiophene‐based monomers, bistributyltin dithienothiophene, and bistributyltin bithiophene; these polymers have been fully characterized. The main difference between the two polymers is the substitution position of the dodecyl side chains in the repeating group. Grazing‐incidence X‐ray diffraction (GI‐XRD) gave clear evidence of edge‐on orientation of polycrystallites to the substrate. The semiconducting properties of the two polymers have been evaluated in organic thin film transistors (OTFTs). The two conjugated polymers 4 and 8 exhibit fairly high hole carrier mobilities as high as μ_ave = 0.05 cm²/Vs (I_ON/OFF = 3.42 × 10⁴) and μ_ave = 0.01 cm²/Vs, (I_ON/OFF = 1.3 × 10⁵), respectively, after thermal annealing process. The solvent annealed films underwent reorganization of the molecules to induce higher crystallinity. Well‐defined atomic force microscopy (AFM) topography supported a significant improvement in TFT device performance. The hole carrier mobilities of the solvent annealed films are comparable to those obtained for a thermally annealed sample, and were one‐order higher than those obtained with a pristine sample. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010