Properties of hydrogenated amorphous silicon suboxide alloys with visible room-temperature photoluminescence

A systematic investigation of hydrogenated amorphous substoichiometric silicon oxide films (a-SiOx:H) is presented. The a-SiOx:H films were prepared by dc magnetron sputtering and were subsequently annealed at temperatures ranging from 300 to 900 degrees C. No formation of nanocrystals is detectable either with X-ray diffraction or with Raman scattering under any annealing conditions. The infrared spectra of the alloys are studied in detail. The SiOx films show visible photoluminescence (PL) at room temperature similar in spectral shape to that seen for porous silicon. The PL intensity-increases upon annealing up to 500 degrees C before decreasing at higher temperatures. A correlation between the luminescence intensity at 700 mm and an infrared absorption band at 880 cm(-1) is found. The assignment of this absorption band at 880 cm(-1) has been clearified as partially oxygen related via hydrogen-deuterium exchange. Optically detected magnetic resonance reveals the existence of triplet excitons with a dipolar radius of 4-5 Angstrom which is associated with the radiative state giving rise to visible luminescence.