Fabrication and reflection properties of silicon nanopillars by cesium chloride self-assembly and dry etching

Cesium chloride (CsCl) self-assembly has been successfully used to fabricate different average diameter CsCl nanoislands ranging from 50 nm to 1 μm through controlling CsCl film thickness, relative humidity and developing time. By process control of inductively coupled plasma (ICP) etching, the silicon nanopillars with different high aspect ratio (2–6), morphologies from column to cone, and diameters from 150 to 800 nm have been made by dry etching with the structure mask of CsCl nano hemispheres. The reflectivity of the silicon nanopillars has also been measured for wavelength from 400 to 1000 nm and shows the best antireflection under 5% by native silicon nanopillars with 200 nm average diameter after 40 min ICP etching. With a layer of SiO2 on silicon nanopillars by thermal oxidation process, the reflectivity reaches to below 2.5% at a large range of wavelength from 400 to 1000 nm.