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

Abstract

A systematic investigation of hydrogenated amorphous substoichiometric silicon oxide films (a-SiO_x: H) is presented. The a-SiO_x: H films were prepared by dc magnetron sputtering and were subsequently annealed at temperatures ranging from 300 to 900°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 SiO_x 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°C before decreasing at higher temperatures. A correlation between the luminescence intensity at 700 nm and an infrared absorption band at 880cm⁻¹ is found. The assignment of this absorption band at 880cm⁻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 Å which is associated with the radiative state giving rise to visible luminescence.