Laser-assisted atom probe microscopy of 2 nm period Si28 / Si30isotope superlattices (SLs) is reported. Three-dimensional distributions of Si28 and Si30 stable isotopes are obtained with sub-nanometer spatial resolution. The depth resolution of the present atom probe analysis is much higher than that of secondary ion mass spectrometry (SIMS) even when SIMS is performed with a great care to reduce the artifact due to atomic mixing. Outlook of Si isotope SLs as ideal depth scales for SIMS and three-dimensional position standards for atom probe microscopy is discussed.
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