The use of inductively coupled plasma mass spectrometry to provide an absolute measurement of surface coverage, and comparison with the quartz crystal microbalance

It is often difficult to obtain an absolute measure of the quantity of an u ltrathin layer of an element deposited onto a dissimilar solid surface, eve n though this is an important parameter for many surface studies. Auger and X-ray photoelectron spectroscopies provide only a relative measure of the quantity of a deposit, and nuclear or ion-scattering spectroscopies are lim ited in the adsorbate/substrate pairs that can be measured and often requir e expensive accelerators that are not readily available. Inductively-couple d-plasma mass spectroscopy (ICPMS) has been used as an ex-situ method to de termine the absolute coverage at sub-monolayer levels in semiconductor proc ess control. However, it does not seem to have been used to date for determ ining surface coverage of adsorbates for other surface-science applications , even though it can do this routinely with an accuracy of few percent. Thi s paper uses ICPMS to determine the coverage of a sub-monolayer of antimony on gold, and shows that the results are consistent with high-precision mea surements taken with a quartz crystal microbalance on the same sample. (C) 1999 Elsevier Science B.V. All rights reserved.