Formation of Si nanorods and hollow nano-structures using high precision plasma-treated nanosphere lithography

Abstract

We report a novel method for the formation of hollow rod silicon nanostructures via plasma treated nanosphere lithography and reactive ion etching. The plasma treatment of polystyrene nanospheres (PS-NS) with O₂ and methanol–O₂ gases is studied as a function of nanosphere size, plasma power and treatment time on a silicon substrate covered by a thin layer of nickel. Applying hydrogen or HCl plasma to already treated polystyrenes, nano-rings and nano-dots can be obtained without any physical or sputtering damage. Large area silicon nano-pillars and hollow silicon nano-structures with inner diameters of 50 nm were obtained by using optimized plasma treatment. These nanostructures show a hexagonal order with good fidelity to the PS-NS patterns. Various characterization techniques such as AFM, SEM, TEM, XPS and FTIR spectroscopy have been exploited to study the samples. The hollow rod structures made using this method will have applications in low power high performance electronic devices, optoelectronic and lithium ion battery devices. Also, a model for the formation of hollow rings is presented.