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A new method for the fabrication of spherical gallium nanoparticles (Ga-NPs) on diamond-like carbon (DLC) layers with high precision in their desired diameter and positioning is presented. The basic principle is the pre-patterning of a DLC film by focused Ga + ion beam irradiation and subsequent annealing. During thermal treatment the evolution of single Ga-NPs with spherical shape on irradiated areas is driven by phase separation and surface segregation of Ga from the supersaturated DLC layer. The shape and size of the implanted areas as well as the ion fluence serve as a Ga reservoir for the nanoparticle (NP) evolution which is strongly correlated with the NP diameter. For the formation of segregation seeds to avoid random segregation of the NPs small spots are additionally implanted with Ga within the irradiated areas. The NP evolution is then assessed with respect to the seed position and the material for the Ga-NP growth is gathered from the surrounding reservoir. Using this technique Ga-NPs were fabricated with a diameter ranging from 40 nm up to several hundred nm. Prospective applications, i.e. in the field of plasmonics, arise from the arrangement in chains as well as in periodical two-dimensional arrays with defined NP size and interparticle distance.

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We derive an improved prescription for the merging of matrix elements with parton showers, extending the CKKW approach. A flavour-dependent phase space separation criterion is proposed. We show that this new method preserves the logarithmic accuracy of the shower, and that the original proposal can be derived from it. One of the main requirements for the method is a truncated shower algorithm. We outline the corresponding Monte Carlo procedures and apply the new prescription to QCD jet production in e + e − collisions and Drell-Yan lepton pair production. Explicit colour information from matrix elements obtained through colour sampling is incorporated in the merging and the influence of different prescriptions to assign colours in the large N C limit is studied. We assess the systematic uncertainties of the new method.

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