Damascene Process for Controlled Positioning of Magnetic Colloidal Nanocrystals

Full text: Potential applications of nanocrystals have been recently discussed in diverse fields ranging e.g. from biomedical, plasmonic, photonic, data storage devices, to Lab-ona- chip concepts, nanocrystals. Significant progress has been achieved in the synthesis of magnetic NCs having well-defined compositions, shapes, structures and sizes. Meanwhile one major challenging issue remains, namely, to produce assemblies of colloidal NCs on well-controlled sites, which is essential to enable separate identification and addressability for single nanoparticle units. In this letter, we report a straight-forward approach for large scale nano-fabrication with high accuracy following the same strategy as the well-established Damascene process in integrated circuit (IC) manufacturing. In the latter, metal interconnects are produced by depositing a thin Cu film on pre-patterned Si wafers and constriction of the Cu film to connecting lines is achieved via a chemical-mechanical back polishing. In our work, the basic idea of this technique is utilized for controlled positioning of NCs by means of deposition on a pre-patterned template, and subsequent NC removal by polishing. The present work demonstrates the potential of such techniques to prepare assemblies of ordered NCs with a size down to 18 nm at low cost and great convenience. Another advantage of this approach is the absence of suspensions or any other solvent during the final processing step, which is an advantage in respect to environment-friendly production. This method allows arranging specific numbers of NCs down to single ones per pit. The structures produced were characterized by scanning electron microscopy (SEM), atomic forceas well as magnetic force microscopy (AFM; MFM) at room temperature. (author)