质量单位千克新定义中单晶硅材料制备同质性精密测量方法

项目名称： 质量单位千克新定义中单晶硅材料制备同质性精密测量方法

项目编号： No.51475440

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 机械、仪表工业

项目作者： 王金涛

作者单位： 中国计量科学研究院

项目金额： 81万元

中文摘要： 通过单晶硅材料测量阿伏加德罗常数是定义质量千克自然基准最有潜力的方法之一。为保证阿伏伽德罗常数测量准确性和稳定性，需要对单晶硅材料中微小密度差异和分布(即同质性)进行精密测量。在固定点静力悬浮测量原理基础上，提出一种新的单晶硅材料临界静力悬浮密度比较测量方法。对临界悬浮状态的单晶硅材料进行动力学研究，通过对静力平衡点附近运动状态分析和测量，在静压力恒定条件下测量出单晶硅材料之间的密度差值，避免了Joule-Thomson效应的影响，标准相对测量不确度3E-7。采用双单晶硅样本实现液体压缩系数和热膨胀系数的一体化测量。通过比较研磨前后单晶硅材料密度差值和质量差值变化，研究单晶硅材料氧化层平均厚度测量方法，以及其时域和空域变化规律；结合Karl-Fisher超微量水分分析方法，研究水分吸收对不同表面体积比单晶硅样本密度差值测量的影响。研究成果对阿伏伽德罗常数精密测量具有重要理论意义和实际价值。

中文关键词： 阿伏伽德罗常数；精密测量；单晶硅；均匀性；密度

英文摘要： Measuring the Avogadro constant NA is one of the most potential resolutions for kilogram quantum standard redefinition based on single crystal silicon material. In order to ensure the accuracy and stability of the Avogadro constant, it is necessary to measure homogeneity in the same single silicon material. Based on static suspension method, one new measurement principle named quasi-hydrostatic method is raised in this project for density comparison measurement. The dynamic analysis of single silicon material in quasi-hydrostatic state is carried out. By keeping pressure constant and measuring the motion parameters of single silicon material near the equilibrium point, the density difference is determined, which avoids the influence of Joule-Thomson effect, and standard relative uncertainty is 3E-7. Simultaneous measurements of compressibility and thermal expansion coefficients of liquid can be accomplished. Based on the same measurement platform,the mean thickness of oxide layer can be determined based on the density and mass difference before and after polish. The study on the influence of surface to volume ration to density measurement will be carried out, and the ultra micro water content is determined by Karl-Fischer method. The results of this research will benefit Avogadro constant measurement both in theoretic support and application.

英文关键词： Avogadro constant;precise measurement;silicon single crystal;homogeneity;density