Papers by Keyword: Nanopillars

Abstract: Anti-reflective polystyrene nanopillar arrays were fabricated by the process of hot embossing where it utilizes the nickel coated anodised aluminium oxide template. Electroless plating being a catalytic method of plating uniformly coats the membrane which increases its strength. The supporting layer of nickel makes AAO template suitable to be used as a mould multiple times. Highly conformal nanopillars of average diameter 400nm and length 30 μm to 50μm were fabricated on the area of ⁓5cm². Hot embossing process ensures repeatability with precision and high throughput. The enhanced light entrapping is attributed to the multiple internal reflection in the nanopillars of high aspect ratio.

Abstract: A qualitative and semi quantitative analysis of anisotropic etching of silicon nanostructures in alkaline solutions was done. Dedicated nanostructures were fabricated on 300mm wafers and their geometric change during wet etching was analyzed, stepwise, by top down SEM or TEM. We challenge the previously described wagon wheel technique towards nanodimensions and describe the pros and cons of the technique using relevant experimental conditions. The formation of specific geometric patterns are explained by the face-specificity of the etch rates. Clear differences in anisotropy were revealed between pillars etched in KOH or in TMAH, and for wagon wheels etched in TMAH or in NH₄OH. Finally etch rates were extracted for the different types of crystal planes and compared.

Abstract: A concept of atomic mechanisms governing strength of nanosized defect-free crystals is presented. It is exhibited that these mechanisms consist in local instability of the lattice. Two main reasons for localization of instability in three-dimension (3D) crystals are analyzed, namely, (i) fluctuation of local stresses induced by thermal vibrations of atoms, and (ii) non-uniform distribution of local stresses caused by a surface tension. Based on this conception, explanations of both the temperature dependence of strength of 3D nanocrystals and scale effect are given. Ideas on the reasons for and regularities of change in strength at transition from 3D to 2D (graphene) and 1D (monatomic chain) crystals are represented. It is shown that dimensionality of crystal is one of the main factors governing strength of defect-free crystals. Experimental values of the strength of carbon monatomic chains are given, which times exceeds the strength of graphene and is the highest attainable level of strength in the world.