Analytical control of the preparation and the chemical grafting of Si/SiO2 heterostructures. Application to the fabrication of silicon microsensors

Abstract Three analytical methods were applied for the analysis of grafted planar heterostructures of Si/SiO 2 : neutron activation, GC and XPS analysis. Neutron activation analysis of bromoalkyl grafts allows the graft density to be quantified. Several parameters were studied: time and temperature of the hydration treatment, as well as temperature of the grafting process. GC allows the grafted alkyl and perfluorinated chains (C≥8) to be identified and quantified. Optimal conditions have been defined to obtain dense alkyl layers. The XPS method allows a qualitative control of the surface to be performed at each physical and chemical process but a quantitative determination of the graft density cannot be done because of the carbon contamination and of the instability of bromoalkyl and perfluorinated grafts under the photon beam. From these results, optimal experimental conditions have been found for the fabrication of grafted selective membranes for chemical and biochemical silicon sensors.