Preparation Of Ordered Si Nanowires Based On Polystyrene Nanosphere Arrays Etched By Ion Beam And Their Mechanism Analysis

Polystyrene(PS)nanospheres can be utilized as a framework and template for fabricating some novel nanomaterials,such as core/shell composite nanomaterials,ordered nanohole arrays and ordered nanowire arrays,and the research and the application of PS nanospheres have attracted broad attention.To further decrease the diameter of Si nanowires is a long-term pursuit of nanosphere lithograghy through reducing the etching rate of PS nanospheres and better controlling the size and morphology of nanospheresthe.In this thesis,the PS nanospheres were exposed to Ar~+ion beam.The evolution of PS nanoparticle traverse and longitudinal diameters with etching time has been studied.The evolution of PS nanoparticle traverse diameter with etching current has been analyzed.The diameter of PS nanoparticles can be controlled effectively in the range from 20 to 180 nm.The mechanism of ion beam etching the PS nanoparticles has been discussed.The evolution rule of the morphology of nanospheres has been revealed.The fastness of non-closed-packed arrays fabricated by inductively coupled plasma etching(ICPE)is compared with that of the arrays prepared by ion beam etching(IBE).Based on the non-close-packed nanoparticle arrays combining metal assisted chemical etching(MACE),the ordered silicon(Si)nanopillars have been fabricated.The traverse diameter of nanoparticles decreases nonlinearly with increasing the exposure time.The longitudinal diameter of PS nanoparticles reduces linearly with prolonging the exposure time.And the etching rate of longitudinal diameter is steady.It is indicated that ion beam etching is an anisotropic etching technology.The traverse diameter of PS nanoparticles reduces nonlinearly.The etching rate of the traverse diameter obviously increase in a long-time ion beam treatment,resulting from the effect of thermal energy accumulated gradually after ion beam bombardment.Through introducing the interruption technology in the etching process,the effect of the thermal energy has been proved.After interrupting the etching process for 30 min,most of the thermal energy can be took away from water cooled target,resulting in a decrease of the etching rate and an increase of traverse diameter.In addition,the better fastness of the nanoparticles prepared by using IBE is observed due to the thermal energy,comparing to that of nanoparticles obtained by ICPE.This result suggests that the non-close-packed arrays of PS particles prepared by employing IBE have a great potential to promote the commercial application of nanosphere lithography.Based on the template with non-close-packed arrays of PS nanoparticles prepared by using IBE,ordered Si nanowire arrays were fabricated by employing MACE.The reason for the aggregation of Si nanowires have been discussed from the surface tension of liquid and the drying time.