AFM characterization of PS prepared in different concentration of hydrofluoric acid

The effect of HF concentration on the surface structure of porous silicon (PS) was carefully investigated by the AFM characterization. The results showed that no pores were present on PS surface which was prepared under the higher concentration of HF (10%). However, the pores were gradually visible with the HF concentration reduction. The main pores diameter was about 100 nm, when the concentration is 5.71%. The data of surface roughness and the main height distribution of the hill both showed an increase with the reduction of concentration, from 6.39 nm increase to 16.9 nm and from 30 nm increase to 90 nm, respectively, which implied that the pores were better exposed under the lower HF concentration.