在预刻蚀的衬底上通过分子束外延直接生长出拓扑绝缘体薄膜的微器件

在利用光刻将拓扑绝缘体外延薄膜加工成微米尺寸结构的过程中,所用的各种化学物质会导致薄膜质量的下降.在实验中,通过在钛酸锶衬底上预先光刻出Hall bar形状的凸平台并以此为模板进行拓扑绝缘体(Bi x Sb1-x)2Te3薄膜的分子束外延生长,直接获得了薄膜的Hall bar微器件,从而避免了光刻过程对材料质量的影响.原子力显微镜和输运测量结果均显示该微器件保持了(Bi x Sb1-x)2Te3外延薄膜原有的性质.这种新的微器件制备方法有助于在拓扑绝缘体中实现各种新奇的量子效应,并可推广于其他外延生长的低维系统.     

气相色谱法同时测定动物饲料中安定和三唑仑残留量

提出了气相色谱法同时测定动物饲料中安定和三唑仑的残留量的方法。饲料经过有机溶剂提取,采用SE-54毛细管柱(30 m×0.32 mm,0.32μm)分离,电子捕获检测器检测,外标法定量。安定和三唑仑的质量浓度均在0.3～60 mg·L~(-1)范围内与其峰面积呈线性关系,检出限(2SN)分别为0.007 1,0.021 3 mg·L~(-1)。方法的平均回收率分别为79.5%～93.1%,81.6%～91.8%,相对标准偏差(n=8)分别为2.11%～4.02%,2.09%～4.61%。     

SYNTHESIS AND STRUCTURE OF CARBON NANOTUBES

The distribution, morphology and structure of carbon nanotubes and buckyonions produced from an arc discharge were investigated by means of scanning electron mi-croscopy and high-resolution transmission electron microscopy, The nanotubes and nanoonions were found to be located mainly near the porous region of the core in the deposited rods and the transition region between the growth ring-shaped graphite sheets. The tube bundles grew freely from carbon particles. Apart from the straight-line tubes, curved and bent tubes were also found. Studies on the structure of them showed that the carbon atomic sheets in the nanotubes displayed a stepped bending. Transverse sectional study predicted a helical structure of the carbon atomic sheets. In addition, the relationship between the number of pentagonal rings and cone angle at the tips of the tubes, as well as the mechanism of the formation of the steplike structure, were discussed.     

INVESTIGATIONS ON THE CRYSTAL STRUCTURE OF 2-(m-CYANOPHENYL)-5-CYANOBENZOTHIAZOLE AND CONFORMATIONS OF ITS ISOMERS

The crystal structure of 2-(m-cyanophenyl)-5-cyanobenzothiazole has been determined by X-ray single crystal diffraction method and its conformational analysis and its two isomers have been carried out by employing the PCILO method. The crystal of title compound belongs to the monoclinic system, space group P2_1/c, a=23.793(7), b=3.852(1), c=27.004(11), β=98.40°(3), Z=8, D_(calc). =1.42g/cm~3, F(000)=1072, the final β=0.048. The crystals of this molecule and its two isomers belong to a same space group, but the packing schemes of the molecules in the unit cell, the separations and the mutual orientation of-C≡N bonds are not same. From the detailed analysis and comparison of their packing schemes in crystal, it can be considered that they may be possible to polymerize to different extent in the solid state by appropriate energy stimulation.     

电极维度对单分子器件伏-安特性的影响

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关于物理实验中的误差分析——电容器充放电时间常数测定的讨论

实验教学的重要性已被越来越多的人所重视.实验课不再是理论课的附属,它已成为培养学生独立工作能力的最有效的手段之一.关于偶然误差,已有较成熟的理论和方法.但在实际问题中,偶然误差和系统误差常常是交织在一起的.而且由于测量方法、实验公式、仪器、测试环境等影响,使系统误差在某些实验中占举足轻重的地位.根据我们的经验,误差的分析首先应从     

二羟基丙二酸根乙二胺合铂的分子结构及晶体结构

用SYNTEX P3/R3四圆衍射仪收集到1672个独立衍射点,晶体属三斜晶系,空间群为P1,α=4526(15)?,b=6.0947(8)?,c=10.1854(15)?,α=106.48(I),β=103.65(I),γ=79.12(I),z=2,用Patterson法得到重原子铂的坐标参数,用Fourier法得到全部非氢原子的坐标参数,用块矩阵最小二乘法修正,最后的R因子为0.055,铂采取d²sp³杂化轨函成键及六配位八面体构型。 关键词：     

完全有序的全同金属纳米点阵列的生长与研究

利用分子束外延在半导体Si(111）衬底上第一次成功地制备了尺寸相同、空间分布均匀的金属纳米团簇阵列，文章作者提出的这种“幻数稳定团簇 模板”的方法并不局限于制备某一种金属团簇阵列，且生长出的金属纳米点阵列非常稳定，用扫描隧道显微镜（STM）原位分析结合第一性原理计算，确定了金属纳米点的原子结构以及这些结构的形成机理。     

Ni_3(Ti_x,V_(1-x))合金系中的长周期结构

本文利用电子衍射及高分辨点阵象实验方法证实了Ni_3(Ti_x,V_(1-x))合金系在铸态下存在有9R,10H,16H,20H,21H,44H等长周期结构以及2H结构。它们与体心四方基体相(结构与Ni_3V相同)及六角基体相(结构与Ni_3Ti相同)有固定取向关系:{001}_(长周期)∥{001}_(Ni_3Ti)∥{112}_(Ni_3V);〈100〉_(长周期)∥〈100〉_(Ni_3Ti)∥〈110〉_(Ni_3V_-)。样品经长期高温退火处理后其它长周期结构均向9R结构转变。     

烯烃配位的过渡金属卡宾配合物的研究XVI:四氟苯并双环[2,2,2]辛三烯三羰基铁的新奇开环反应-新型螯合双烯丙基三羰基铁配合物的合成和结构

四氟苯并双环[2,2,2]辛三烯三羰基铁(C12H6F4)-Fe(CO)3(1)与芳基锂试剂ArLi(Ar=C6H5、o-, m-, p-CH3C6H4、p-CH3OC6H4、p-CiC6H4), 在低温下反应, 生成的酰羰基锂盐中间体用三乙基氧 -四氟硼酸盐(Et3OBF4)在水溶液中于0℃进行烷基化时, 双环烯烃配体开环, 生成组成为(C12H6F4)(CO)2FeC(OC2H5)Ar的螯合双烯丙基二羰基铁配合物(2-7), 配合物5的晶体属单斜晶系, 晶胞参数为;a=16.870(4), b=13.707(4), c=19.361(4)A, β=107.92(2)°.V=4259(1)A^3, Z=8, 空间群为C^62h-C2/c, 最后的偏离因子R=0.0409, Rw=0.0391。