The definition of features on the nanometre length scale (NLS) is impossible via
conventional lithography, but can be done using extreme ultraviolet, synchrotron-radiation,
or electron beam lithography. However, since these techniques are very expensive and still
in their infancy, their exploitation in integrated circuit (IC) processing is still highly
putative. Geometries on the NLS can however be produced with relative ease using the
spacer patterning technique, i.e. transforming vertical features (like film thickness) in
the vicinity of a step of a sacrificial layer into horizontal features. The ultimate
length that can be produced in this way is controlled by the steepness of the step
defining the sacrificial layer, the uniformity of the deposited or grown films, and
the anisotropy of its etching. While useful for the preparation of a few devices
with special needs, the above trick does not allow by itself the development of a
nanotechnology where each layer useful for defining the circuit should be on the NLS and
aligned on the underlying geometries with tolerances on the NLS. Setting up such a
nanotechnology is a major problem which will involve the IC industry in the post-Roadmap
era. Irrespective of the detailed structure of the basic constituents (molecules,
supramolecular structures, clusters, etc), ICs with nanoscopic active elements can hardly be
prepared without the ability to produce arrays of conductive strips with pitch
on the NLS. This work is devoted to describing a scheme (essentially based on
the existing microelectronic technology) for their production without the use
of advanced lithography and how it can be arranged to host molecular devices.
This work presents a study based on x-ray photoelectron spectroscopy of the reaction of hydrogen-terminated silicon with 1-alkynes as a route for the functionalization of the (100) surface of silicon. The study (i) demonstrates that the grafting of hydrocarbon moieties is possible by simple exposure of the silicon surface to a liquid alkyne, (ii) shows that the derivatization protects the silicon against oxidation in air, (iii) indicates that the process occurs via hydrosilation of the alkyne at the hydrogen-terminated surface and (iv) suggests that grafted moieties contain in large part an unreacted π bond.
A quantitative angle-resolved XPS analysis was carried out of the carbonaceous films resulting from the derivatization under mild thermal activation of nearly flat, terraced, dihydrogen-terminated, 1 × 1 (100) Si with 1-octene or 1-octyne. The analysis of the C 1s signal gave evidence for the presence of carbon in carbide configuration (Si-C bonds) at the substrate-film interface, in addition to the alkanic carbon and adventitious oxidized carbon (C-O bonds) produced by the oxidizing impurities flawing the reaction. Assuming the surface as uniformly covered, the analysis showed that for both reactants the films were closely packed.
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