V H S Moorthy, Michael Hoh, Sumanta Kumar Sahoo, PSVRV Tejasvi, Preeti Agarwal and Vaibhav Raina
Manipal Institute of Technology (under graduate);
currently at Purdue University (Masters)
Nanosphere lithography (NSL) – liquid surface self assembly technique- is an inexpensive, table top and scalable technique for the fabrication of periodic nanostructures of varying size, shape and periodicity. The self assembled mono-dispersed 2D colloidal crystals (polystyrene nanospheres of 450 nm size) on pre-treated Si (100) substrate is used as a mask to create periodic nanostructures of Ag. The polystyrene nanospheres are mono-dispersed on air-DI water interface by using custom-built pipette. A surfactant (Triton X-100/Sodium dodecyl sulphate) is added to the water surface to reduce the surface tension and condense the particles into a closely packed monolayer. Then the hydrophilic Si (100) substrates are introduced beneath the water surface and the water is carefully drained such that the polystyrene film is descended onto the substrate and subsequently left for drying in a clean environment. The resultant self-assembled polystyrene templates are characterized for different defect structures- by optical microscopy and scanning electron microscopy (SEM –JEOL8610) and modifications in the deposition technique are effected to obtain larger domains of hexagonally close packed (hcp) structures of polystyrene nanospheres. On this polystyrene hcp template, an ultrathin film (320 Å) of Ag is deposited by vacuum evaporation technique. The periodic metallic (Ag) nanostructures are obtained by subsequent removal of the under layer hcp structure of polystyrene nanospheres. The periodic nanostructures are characterized by scanning electron microscopy. The periodic structure is characterized by triangular shaped nanoparticles with average size of 120nm and periodicity 450nm.