Fig. 1. Cross-sectional view of the porous silicon based micro-direct ethanol fuel cell (DEFC) stack. The macroporous Si layer provides channels for contact of air and fuel with the electrodes. Reprinted with permission from S. Aravamudhan, A. R. A. Rahman, S. Bhansali, Sens. Actuators A 2005, 123–124, 497.

Fig. 2. Hole injection can occur via an acceptor level such as A⁺, that lies below the VBM but not one such as B⁺ that lies above it.

Fig. 3. The PL from films etched with Fe³⁺ (E₀ = 0.47 V versus the standard calomel electrode (SCE)) peaks at 696 nm, compared to 654 nm for HNO₃ (E₀ = 0.66 V) and 604 nm for .

Fig. 4. Experimental energy diagram of the interface between Si and a blank fluoride solution (- - -) at pH 2 and fluoride solution (—) in the presence of 1 mM Pt²⁺/Pt. Reprinted with permission from P. Gorostiza, P. Allongue, R. Diaz, J.R. Morante, F. Sanz, J. Phys. Chem. B 2003, 107, 6454.

Fig. 5. A cross-sectional electron micrograph of a por-Si film composed of vertical Si nanowires. The film was created by etching in a 4.6 mol dm⁻³ HF + 0.02 mol dm⁻³ AgNO₃ solution for 60 min at 50 °C. Reprinted with permission from K. Q. Peng, Z. P. Huang, J. Zhu, Adv. Mater. 2004, 16, 73.