A close to unity and all-solar-spectrum absorption by ion-sputtering induced Si nanocone arrays

Si nanocone arrays are formed on Si(100) by Ar(+) ion sputtering combined with metal ion co-deposition. The aspect ratio of Si cone is found to increases steadily with increasing sample temperature, but decreases slowly with increasing ion dose. Furthermore, the height and base diameter of Si cone increase monotonously with increasing dose at a constant temperature. The absorptivity increases in general with increasing aspect ratio and height. A close to unity and all-solar-spectrum absorption by the nanostructured Si is finally achieved, with the absorbance for λ = 350 to 1100 nm being higher than 96%, and that for λ = 1100 to 2000 nm higher than 92%. Photocurrents for different Si samples are also investigated.