Fig. 1. Optical microscope topography of black silicon samples obtained with various preparation parameters. Scan line spacing are 180 μm (a), 100 μm (b), 4 μm (c), respectivly; Orthogonal scanning: Scan line spacing are 180 μm (d), 100 μm (e), 4 μm (f), respectively

Fig. 2. Sectional SEM image of black silicon sample

Fig. 3. Silicon surface reflection spectra with different scanning spacing by orthogonal scanning

Fig. 4. PL spectra of black silicon prepared by line scanning before and after step oxygen blowing annealing

Fig. 5. (a) PL spectra of black silicon prepared by orthogonal scanning before and after step oxygen blowing annealing;(b) TEM image of black silicon quantum dots prepared by orthogonal scanning method

Fig. 6. Local state emission of black silicon at 630 nm. (a) PL spectra; (b) Physical model