Fringing Field Directed Assembly of Nanomaterials

This letter reports on a new gas-phase printing approach to deposit nanomaterials into addressable areas on a surface with 50 nm lateral accuracy. Localized fringing fields that form around conventional resist patterns (PMMA and SiO2) with openings to a silicon substrate are used to direct the assembly of nanomaterials into the openings. Directed assembly was observed due to a naturally occurring inbuilt charge differential at the material interface that was further enhanced by corona charging to yield a field strength exceeding 1 MV/m in Kelvin probe force microscopy (KFM) measurements. The assembly process is independent of the nanomaterial source and type: an evaporative, plasma, and electrospray source have been tested to deposit silicon and metallic nanoparticles. The results suggest a potential route to form nanolenses on the basis of charged resist structures; a 3-fold size reduction has been observed between the structures and the assembled particles. Applications range from the integration of functional nanomaterial building blocks to the elimination of lift-off steps in semiconductor processing.