The chemical modification caused by prolonged exposure to X-rays on a series of para-substituted phenyl moieties (-NO2, -CN, -CHO, -COOH, -CO2Me, and -CO2(1)Bu) at the surface of thiolate-Au self-assembled monolayers (SAMs) has been investigated by X-ray photoelectron spectroscopy (XPS). Furthermore, the influence that the phenyl group has on the chemical modification induced by the X-ray irradiation on the SAMs was investigated by comparing the XPS results obtained from irradiation on a NO2-aromatic-terminated SAM (6-(4-nitro-phenoxy)-hexane-1-thiolate (NPHT)) and NO2-aliphatic-terminated SAM (thioacetic acid S-(12-nitrododecyl) ester (TNDDE)). The NPHT and TNDDE SAMs have been shown to behave differently to X-ray exposure. The irradiation of the NPHT SAM led to the reduction of the nitro (-NO2) moiety to the amine (-NH2) moiety, as shown by the decrease in the intensity of the N 1s photoelectron peak for -NO2 (406 eV) in the XPS spectra with the concomitant increase in the N 1s photoelectron peak for -NH2 (399 eV). On the TNDDE SAM, XPS showed the -NO2 photoelectron peak again decreasing with prolonged X-ray irradiation whereas no peak was observed at 399 eV; therefore, the -NO2 moieties are selectively cleaved. No change was observed on the other functionalized monolayers apart from the -CO2(t)Bu-functionalized monolayer, where after 100 min of X-ray irradiation approximately 11% of the carbon content was lost. The S 2p and O 1s spectra remained unchanged during the irradiation suggesting the conversion of the -CO2(t)Bu to the -COOH moiety, although the conversion was not complete because the tertiary butyl moiety contributes 25% to the total carbon content of the SAM. Also, there was no evidence of the molecules desorbing from the substrate for any of the SAMs studied during the X-ray irradiation as shown by no change in the S 2p and C 1s XPS spectra taken during the X-ray irradiation.

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A spectrometer is described with particular reference to its resolution and to a novel quick change specimen holder. For the benefit of new workers in the field, the need for four-point probe measurements is reiterated, together with the importance of suitable cleaning procedures during sample preparation and rigorous electrical screening of the spectrometer. A high resolution spectrum of benzoic acid is presented together with spectra of 1,2-, 1,3-and 1,4-benzenedicarboxylic acids. Brief mention is made of the use of a computer data acquisition system with the latter, full details being described elsewhere.

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The plasmon loss region of x-ray photoelectron spectra has been analyzed for chemically vapor deposition diamond in order to assess the nondiamond carbon (NDC) levels present. A semiquantitative method for expressing the quality of the diamond, based upon the ratio of the diamond bulk plasmon to the main carbon 1s line is presented and a figure of merit defined. A comparison with Raman spectroscopy shows that this technique compares well in terms of range and sensitivity to NDC levels.

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Exposure of Langmuir-Blodgett (LB) films of a C 60 adduct supported on silicon wafers to UV light leads to cross-linking of the C 60 moieties, which are resistant to removal by solvent exposure, whereas unexposed moieties are readily removed. This process provides a convenient and simple route for the fabrication of highly conjugated surface-attached structures, with dimensions ranging from micrometres (using masks) to a few tens of nanometres using light emitted from a scanning near-field optical microscope (SNOM). The SNOM writing velocity was found to significantly affect the lateral resolution and the height of the three-dimensional nanostructures. Increasing the writing velocity from 0.3 to 2 mm s À1 resulted in a decrease in the width of the structures from 240 nm to 70 nm (corresponding to the SNOM aperture diameter), respectively, and a reduction in the height from 8 nm (the thickness of the original film) to 3 nm, respectively. This approach provides a simple, direct route to surface-bound nanometre scale assemblies of C 60 .