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| Research on Comparison Measurement of Single-crystal Silicon Sphere Density Based on Pressure Floatation Method |
| LIU Zi-yong,WANG Jin-tao,XU Chang-hong, LUO Zhi-yong |
| National Institute of Metrology, Beijing 100013, China |
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Abstract To overcome the influence of liquid surface tension on the density measurement of single-crystal silicon sphere with hydrostatic method, pressure-of-flotation (PF) method and measurement system were developed to carry out the comparison measurement of single-crystal silicon sphere density. On the condition of certain temperature, the pressure of liquid was adjusted, which caused the change of liquid density, and the standard and measured single-crystal silicon spheres could be suspended in the liquid stably. By measuring liquid temperature, pressure and suspension heights, the density difference was determined. Double-level temperature control system was used to achieve stable temperature within ±0.25 mK. The liquid compress coefficient was determined by the linear equation of temperature-pressure suspension condition. It was verified by experiments that the density difference of single-crystal silicon spheres could be measured with high precision, and the standard relative uncertainty is 2×10-7.
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2013, Vol. 34 
