We report polarized femtosecond laser-light-mediated growth and programmable assembly of photoreduced silver nanoparticles into triply hierarchical micropatterns. Formation of erected arrays of nanoplates with a thickness as small as λ/27 (λ, the writing laser wavelength) level is demonstrated. The growth mechanism of nanoplates has been clarified: (i) the excited surface plasmons enhance the local electric field and lead to spatially selective growth of silver atoms at the opposite ends of dipoles induced on early created silver seeds; (ii) the optical attractive force overcomes electrostatic repulsion in the enhanced local electric field to assemble the silver nanoparticles directly. The triply hierarchical micropattern shape and location, the nanoplate orientation, and thickness are all attained in controlled fashion.
Gold nanodots were used as the precursory material to form micronanopatterns under pinpoint scanning by a tightly focused femtosecond laser beam. Different from the widely reported metal ions photoreduction mechanism, here gradient force in an optical trap generated around the laser focus is considered as the major mechanism for particle accumulation (focusing). It has been proven to be an effective method for gold micronanostructure fabrication, and the electronic resistivity of the resulting metals reached as high as 5.5 × 10(-8) Ω m, only twice that of the bulk material (2.4 × 10(-8) Ω m). This merit makes it a novel free interconnection technology for micronanodevice fabrication.
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