Patterned arrays of gold nanoparticles in two dimensions were prepared by the electron beam reduction and subsequent thermolysis of gold(I)−thiolate complexes on silicon surfaces. The array line widths are <50 nm and they are composed of small gold nanoparticles (average diameters from 2 to 4.5 nm). Variation in the electron beam dose allows for the variation of the interparticle distances in a given sample.

A new strategy to prepare and precisely assemble small gold nanoparticles in true one-dimensional lines is reported. This template-free technique allows one to control the nanoparticle size and interparticle distances, while precisely positioning the large scale 1-D assemblies on the surface.

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In this work we show that improved performances of terahertz emitters can be obtained using an ion implantation process. Our photoconductive materials consist of high-resistivity GaAs substrates. Terahertz pulses are generated by exciting our devices with ultrashort near-infrared laser pulses. The ion implantation introduces non-radiative centres, which reduce the carrier lifetime in GaAs. The presence of the charged defects also induces a redistribution of the electric field between the antenna electrodes. This effect has a huge influence on the amplitude of the radiated terahertz field. Results obtained as a function of the laser excitation power are discussed and a comparison of the performance of these devices with a conventional antenna-type emitter is given.