Surface Wettability of Oxygen Plasma Treated Porous Silicon

Figure 5

Schematic of oxygen species O* diffusing into the pores. In the pore of small radius 𝑟 (left pore), the concentration of O* inside the pore [O*]_pore is dependent on 𝑟 due to collision with pore walls based on Knudsen model, while for pore size of sufficiently large 𝑟 (right pore), [O*]_pore is almost equal to the bulk O* concentration in the chamber [O*]_bulk.