Lattice comparison measurement of silicon single crystals by a self-referenced lattice comparator

We performed lattice comparison measurements between 28Si-enriched crystals using a self-referenced lattice comparator (SRLC). The relative lattice spacing difference between two crystals sectioned from the same ingot were measured, showing agreement with values calculated from impurity and vacancy corrections, as well as with those obtained by other measurement techniques. Further comparison involving crystals from different ingots enabled an independent determination of the {220} lattice-plane spacing of a 28Si enriched crystal as 192.014 712 91(55) nm, confirming previously reported values. When applied to the realization of the kilogram via the X-ray crystal density (XRCD) method, the uncertainty contribution from the SRLC measurement corresponds to 8.4 g uncertainty in the mass of a 1-kg silicon sphere, supporting its role in the accurate realization of the kilogram.