This work deals with the interest in ion beams for controlling nanocrystals synthesis in glasses.We show two different ways to reach this aim, insisting on importance of redox phenomena induced by thepenetration and implantation of ions in glasses. We first show that we can use the great energy density depo-sited by the ions to tailor reducing conditions, favorable to metallic nanocrystal precipitation. In particular,we show that microscopic mechanism of radiation induced silver precipitation in glasses are analogous tothe ones of classical photography. Ion beams can also be used to overcome supersaturation of elements in agiven matrix. In this work, we synthesized lead chalcogenide nanocrystals (PbS, PbSe, PbT e) whose opticalproperties are interesting for telecom applications. We demonstrate the influence of complex chalcogenidechemistry in oxide glasses, and its relationship with the observed loss of growth control when nanocrystalsare synthesized by sequential implantation of Pb and S in pure silica. As a consequence of this understanding,we demonstrate a novel and controlled synthesis of PbS nanocrystals, consisting in implanting sulfur into aPb-containing glass, before annealing. Choice of glass composition provides a better control of precipitationphysico-chemistry, whereas use of implantation allows high nanocrystal volume fractions to be reached. Ourstudy of IR emission properties of these nanocrystals shows a very high excitation cross section, and evidencefor a dark exciton emitting level.
