Investigation of Morphological and Optical Properties of Stain Etched Silicon

In the present work, we present the fabrication of ordered porous pyramids and silicon macropores by stain etching which is a low coast and simple chemical method. The etching of silicon surfaces is made in a solution based on... [ view full abstract ]

In the present work, we present the fabrication of ordered porous pyramids and silicon macropores by stain etching which is a low coast and simple chemical method. The etching of silicon surfaces is made in a solution based on vanadium oxide (V2O5)/hydrofluoric acid solution (HF). The goal of this work is to study the effect of metal catalyzer, such Palladium (Pd) and Silver (Ag), on the structures properties (morphological, structural and optical). For the metal assisted etching, we choose metals that differ with respect to their catalytic effect. Ag is a poor hydrogen recombination catalyst, though it is more effective than Si and Pd is an excellent hydrogen recombination catalyst.
Thereby, we could confirm the self-cleaning effects of the fabricated structures as well as the optical properties.
P-type silicon wafers with resistivity of 1 - 10 Ωcm, were used as substrate. The samples were divided into three groups: one group containing four Si samples, another group containing four Si samples with a thin film of Palladium (Pd) deposited and the last group containing four Si samples with a thin film of Silver (Ag) deposited. The three groups were etched in a mixture of HF (49%) and V2O5 (98%), for a period of 30, 60, 90, and 120 min. FTIR measurements of Si, Pd/Si and Ag/Si etched in HF/V2O5 solution revealed the presence of hydride species (SiHx) on the surface.
The structures obtained by etching Si samples in HF/V2O5 for an etching time of 30 min show porous silicon layers which appear in form of islands separated by large channels. When the etching duration is extended to 1 h, the density of pyramids structure increases evidently. When Si surface is covered by a thin film of Ag, the structures obtained by increasing time of etching, are almost the same observed by etching Si surface covered by a thin Pd film which consists in a formation of macropores with pyramidal structures inside. The Ag/Si structures obtained showed a contact angle of 148.6 ±2° after organic treatment.