Progress in the measurement of lattice spacing d(220) of silicon

X-ray and optical interferometry is applied to the measurement of silicon lattice spacing. The previously reported standard deviation 0.16/spl times/10/sup -6/ has been reduced to 0.05/spl times/10/sup -6/. The d(220) is 192015.593(0.01) fm after correction of lattice strain by carbon and oxygen.