Activation of blue emission from oxidized porous silicon by annealing in water vapor

It is reported that annealing of oxidized porous silicon in water vapor at about 250 °C drastically enhances its blue emission. Infrared absorption studies indicate that this annealing increases all the absorption peaks related to O–H vibrations, except for that of free silanol which disappears completely. No traces of carbon-related signals are observed. The latter result makes a clear objection to blue-band luminescence models based on adsorbed carbon compounds. Although the possibility of silanol-related origins cannot be ruled out, we suggest that some passivation effect of adsorbed hydroxyls on Si nanostructures surrounded by SiO₂ is also likely. © 1998 American Institute of Physics.