Surface characterization of a National Bureau of Standards glass reference material by californium-252 particle desorption mass spectrometry

Abstract

National Bureau of Standards glass Standard Reference Materials have been characterized by particle desorption mass spectrometry (PDMS). Surface cleaning procedures, such as etching with HF or kiloelectronvolt ion sputtering, allow the detection of low-level dopants. Differences observed in the PDMS spectra before versus after sputter removal or surface hydration layers reflect the sensitivity of this technique to the chemical environment of the sample region from which the analytical signal originates. The small number of particles (ca. 10/sup 5/) needed to obtain a useful spectrum minimizes sample charging problems often encountered in surface analysis of insulating materials. Li, Be, Rb, and Cs were detected in NBS glass, nominally doped at the 500-ppm level. Only Li was detected in the 50-ppm doped glass. Therefore, the detection limits range between 50 and 500 pp, The use of a dual grid assembly for the acceleration of the desorbed ions resulted in increased efficiency of the time-of-flight mass spectrometer.