Effect of porous layer engineered with acid vapor etching on optical properties of solid silicon nanowire arrays

Abstract

In this paper, we report, for the first time, an investigative study involving the engineering of lightly doped porous silicon nanowire arrays (pSiNWs) by exposing solid silicon nanowire arrays (SiNWs) to an acid vapor emanating from HF/HNO3 hot solution. SEM and TEM images exhibit vertically distributed SiNW arrays on the whole silicon (Si) surface with relatively smooth surface sidewalls. By submitting the SiNW arrays to Acid Vapor Etching (AVE), they become porous with a substantial decrease in their densities and lengths. Increasing etching duration leads to a higher porosity without affecting the wire diameter which remains almost constant nearly 100nm. Exceeding a critical etching duration, a porous structure is observed superseding the SiNW structure. The morphological characterizations have been correlated to the optical properties. We note a blue shift of the strong visible photoluminescence (PL) bands after AVE treatment due to the decrease of the silicon quantum dots diameter (Si-QDs). UV–Visible measurement shows a decrease of the total reflectivity by 5% after AVE treatment.