Measurement of the 100 nm NIST SRM 1963 by differential mobility analysis

The number mean diameter of 100 nm NIST Standard Reference Material (SRM) 1 963 was measured to be 100.7 nm with an expanded uncertainty at the 95% con fidence level of 1.0 nm by measurement,vith the differential mobility analy zer (DMA). The low level of uncertainty resulted from the use of the 1.0 mu m SRM 1690 for calibrating the DMA. The largest single component of the Ty pe B (systematic) uncertainty was a 0.29 nm uncertainty in the calibration diameter. Measurements of the 0.3 mu m SRM with the calibrated DMA give res ults within 0.001 mu m of the certified diameter. Results obtained by other investigators using transmission electron microscopy (TEM), angle dependen t light scattering, electro-gravitational aerosol balance, and atomic force microscopy are consistent with this DMA value. The 100 nm NIST SRM 1963 an d the Japanese 100 nm Calibration Standard are shown to differ by 10% based on TEM analysis and DMA measurements. This size difference has a significa nt effect on the calibration of scanning surface inspection systems and opt ical particle counters.