Denis Mariolle

Local silicon doping as a promoter of patterned electrografting of diazonium for directed surface functionalization

We study the influence of locally doped silicon substrates on the electroreduction of diazonium salts. Our results show that the reduction of diazonium salts occurs at moderate potentials compared to the flat band potential of the semiconducting electrode. The underlying doping directs the electrografting, preferentially over doped areas of the substrate. High resolution spatially resolved X-ray photoelectron spectroscopy analysis using a new X-ray photoelectron emission microscope (XPEEM) and soft X-ray synchrotron radiation yields the thickness of the native oxide of the micron scale doped pattern on the substrate. The results as a function of both parameters—reduction potential compared to the flat band potential and thickness of the oxide layer—are discussed. These new results are then compared to data obtained on the localized electrografting of vinylic monomers.

Aspects of lateral resolution in energy-filtered core level photoelectron emission microscopy

Lateral resolution is a major issue in photoelectron emission microscopy (PEEM) and receivedxa0much attention in the past; however a reliable practical methodology allowing for inter-laboratory comparisons is still lacking. In modern, energy-filtered instruments, core level or valence electrons give much lower signal levels than secondary electrons used in still most of the present experiments. A quantitative measurement of the practical resolution obtained with core level electrons is needed. Here, we report on critical measurements of the practical lateral resolution measured for certified semiconducting test patterns using core level photoelectrons imaged with synchrotron radiation and an x-ray PEEM instrument with an aberration-corrected energy filter. The resolution is 250 ± 20xa0nm and the sensitivity, 38xa0nm. The different contributions to the effective lateral resolution (electron optics, sample surface imperfections, counting statistics) are presented and quantitatively discussed.

Photoemission induced bias in two-dimensional silicon pn junctions

Spectroscopic x-ray photoelectron emission microscopy was used to study the role of the pn junction on imaging of micron scale n- and p-doped silicon patterns epitaxially grown on p- and n-type substrates, respectively. In the closed n-doped patterns, contrast with respect to open patterns is observed in both work function and Si 2p binding energy. Reverse bias at the junction creates a shift of electrical potential induced by photoemission in the closed patterns. No shift is observed for p-doped patterns on n substrate, pointing to the importance of doping combination and pattern geometry in the contrast observed in electron microscopy.