Metal overlayers on organic functional groups of self-organized molecular assemblies .7. Ion scattering spectroscopy and x-ray photoelectron spectroscopy of Cu/CH3 and Cu/COOCH3

X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) were used to characterize octadecanethiol [ODT, HS(CH2)(17)CH3] and methylmercaptohexadecanoate [MMHD, HS(CH2)(15)COOCH3] self-assembled monolayers (SAMs) before and after depositing up to 1.0 nm Cu at ca. 10(-7) Torr. Results from XPS O Is, Cu 2p, and C Is spectra do not indicate that a complex is formed (no chemical shifts) between Cu and the COOCH3 of MMHD or ODT organic functional groups (OFG) at 295 K. Although no direct evidence for Cu/COOCH3 interactions is evident, the initial value for ISS Cu peak intensities for 1.0 nm of Cu on COOCH3 of MMHD requires 7 h before it disappears compared with less than 150 min for Cu on CH3 of ODT. These times are also bracketed from XPS results. which are less sensitive than ISS to loss of copper from the M/SAM surface. The longer penetration time through MMHD versus ODT might be explained by weak interactions between Cu and COOCH3 of MMHD by different defect densities in the SAMs. The actual Cu deposition versus a layer-by-layer growth model and narrowing of the XPS Cu 2p peaks both provide support for formation of Cu clusters on the OFGs prior to penetration to the SAM/Au interface. (C) 1997 American Vacuum Society.