Molecular interaction of ozone with silicon nanocrystallites: a new method to excite visible luminescence

A new effect of luminescence excitation in porous silicon under ozone adsorption has been studied. Ozone-induced luminescence and photoluminescence (PL) intensities decay during ozone exposure showing strict correlation. Luminescence degradation is accompanied with oxide growth and Pb center generation in porous silicon as revealed by IR and ESR spectroscopy. The linear interrelation between emitted light flux and oxide concentration in the course of ozone adsorption is founded. The correlated shifts of ozone-induced and PL spectra are observed when the porosity is changed. A mechanism of the effect we propose is that dissociative ozone adsorption produces exothermic reaction of backbond oxidation of silicon crystallites. Then, a dissipating energy is utilized for interband carrier transitions in electronic extended states of nanometer-size silicon crystallites. The consequent radiative relaxation proceeds like in the case of photoexcitation.