DETERMINATION OF DIFFERENCES IN THE DENSITY OF SILICON SINGLE-CRYSTALS BY OBSERVING THEIR FLOTATION AT DIFFERENT PRESSURES

The method of observing the pressure of flotation, previously used for measuring density differences of liquids, has been applied here for the determination of very small density differences of silicon single crystals. The hermetically sealed flotation vessel containing a 2 : 1 mixture of 1,2,3-tribromopropane and 1,2-dibromoethane is connected through a flexible tube to a second vessel, the height of which can be changed by about half a meter. The hydrostatic pressure can thus be varied, yielding liquid density (rho(f)) variations within a range of 3 . 10(-6) . rho(f). Density differences have been measured with a relative uncertainty of 10(-7), and a resolution of 10(-8) . rho(f) has been attained.