Quantitative measurement of local elasticity of SiOx film by atomic force acoustic microscopy

<正>In this paper the elastic properties of SiO_x film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy(AFAM) in which the sample is vibrated at the ultrasonic frequency while the sample surface is touched and scanned with the tip contacting the sample respectively for fixed point and continuous measurements.The SiO_x films on the silicon wafers are prepared by the plasma enhanced chemical vapour deposition(PECVD).The local contact stiffness of the tip-SiO_x film is calculated from the contact resonance spectrum measured with the atomic force acoustic microscopy.Using the reference approach,indentation modulus of SiO_x film for fixed point is obtained.The images of cantilever amplitude are also visualized and analysed when the SiO_x surface is excited at a fixed frequency.The results show that the acoustic amplitude images can reflect the elastic properties of the sample.     

二维类三角晶格声子晶体的声学带隙特性分析

首先划分7种类三角晶格声子晶体按三角点阵排列,并推导它们的结构因子,然后利用平面波展开法数值计算了类三角晶格水/水银声子晶体的能带结构,分析了带隙的各向同性以及归一化半径对带隙的影响.结果表明:(3.4.6.4)品格、(34.6)晶格、(3.6.3.6)晶格、(63)晶格水/水银声子晶体可以产生较宽频率范围的带隙;(3.12.12)晶格和(4.6.12)品格水/水银声子晶体存在很窄低频带隙;单胞含6个和3个“原子”水/水银声子晶体容易形成各向同性带隙;选取归一化半径分别为0.38和0.28,使类三角晶格水/水银声子晶体的第1和第2带隙都获得最大值.     

影响红外吸收法测定钢中超低碳含量稳定性的因素对比研究

在国家标准GB/T 20126-2006的基础上,讨论了影响测定超低碳钢中碳含量稳定性的几点因素。认为试样表面碳,主要是表面化合碳对测定钢中超低碳有较大影响,该部分可通过采用预加热的方式进行消除,同时也讨论了样品制备、坩埚及助熔剂对测定结果的影响。结果显示,严格按照国标GB/T 20126-2006所述的预处理方式,可最大程度的减小测定钢中超低碳含量时的波动性。