Selective growth of silver nanoparticle arrays on nanoimprinted sol-gel silica patterns

Selective growth of silver nanoparticles on ~100 nm thick silica patterns produced by nanoimprint method has been successfully demonstrated using either (1) thermo-induced reduction or (2) room temperature electroless deposition (ELD) without removing the ~25 nm thick residual layer left by nanoimprint process. This selectivity was achieved by silane additive, (3-mercaptopropyl)trimethoxysilane (3-MTS), which was added to the silica matrix to control nucleation and growth of silver. The presence of silver nanoparticles was confirmed by EDX and UV-vis spectrum, and the density, distribution, and size of silver particles were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Silica film heat-treated between 400 and 600 °C resulted in silver particles of 100-120 nm diameter with a linear density of 2.63-3.36 μm(-1), while the film treated by room temperature ELD produced silver particles of 67 nm diameter with a linear density of 5.65 μm(-1). The selective growth ratio based on particle density on pattern area versus residual layer is 12.92 and 20.31 for high- and room-temperature processes, respectively, whereas the samples without 3-MTS shows low selective growth ratio of 1.22 and 1.04. These results prove that both approaches are fast and effective, suggesting their potential to produce other type of nanoparticle arrays directly on nanoimprinted patterns.