HIGH-RESOLUTION ALGORITHM FOR QUANTITATIVE ELEMENTAL DEPTH PROFILING BY ANGLE-RESOLVED X-RAY PHOTOELECTRON-SPECTROSCOPY

We have developed an algorithm for analysis of angle-resolved x-ray ph otoelectron spectra that allows quantitative depth profiling of the su rface elemental composition with atomic depth? resolution. This method has nondestructively yielded valuable new information about adsorbate bonding and conformation for several of the chemical systems listed b elow, permitting adsorbate modeling at the atomic level. The computati on implements a profile-smoothing search and gives error limits on the profiles. The method is capable of computing at least six simultaneou s elemental profiles, is robust to as much as 10% experimental error, and performs well even under unfavorable conditions such as patchy ove rlayers, complex organic adsorbates (such as DNA), and trace elemental quantities (<10%). The depth profiles obtained for Cu on Ru(0001), Si O2 on Ag(111), and for sulfur-modified DNA, CI(CH2)(3)SH, and cystamin e adsorbed onto Au(lll), show close correspondence to scale molecular models and to expected stoichiometries for the surface composition. (C ) 1997 American Vacuum Society.