LIGHT-EMISSION FROM CRYSTALLINE SILICON AND AMORPHOUS-SILICON OXIDE (SIOX) NANOPARTICLES

Bright orange-red light emission was observed from single crystal sili con nanoparticles and silicon oxide (SiOx) nanoparticles. The emission peak was recorded at about 1.5 eV both at room temperature and 77K. V arying the mean silicon particle size, we observed no effect of partic le diameter on the emission wavelength. Amorphous silicon oxide (SiOx) nanoparticles also showed essentially the same emission spectrum as t he crystalline particles. The absence of change in the photoluminescen ce (PL) spectrum with variations in particle size and crystallinity in dicates that quantum confinement is not the controlling PL mechanism. An examination of the hydrogen content with relation to the PL intensi ty showed no direct correlation; however, all samples did contain some hydrogen, so its effect on PL cannot be ruled out. To test for the pr esence of photoluminescent siloxene on the surface of the particles, n itric acid was applied; a violent reaction occurred with the silicon p articles, while the SiOx particles showed no reaction. Taken in conjun ction with the emission data, these experiments demonstrate that the P L of the SiOx is also not dependant on siloxene. Evidence points to an amorphous coating as the source of photoluminescence.