Photoluminescence from SiOx layers containing amorphous silicon nanoparticles



The article summarizes the main results of a systematic study on the preparation of amorphous SiOx thin films with various contents (1.1≤ x ≤1.7) by thermal evaporation of SiO in vacuum, growth of amorphous Si nanoparticles by furnace annealing at 973 K for various times (5–200 min) and investigation of photoluminescence (PL) from the annealed films. Infrared (IR) transmission measurements prove the annealing-induced phase separation. Raman scattering data indicate the formation of pure amorphous Si phase. Intense room-temperature PL is detected from films with x ≥ 1.5, visible with a naked eye. Two PL bands are resolved, peaked at around 2.3 eV and in the range 1.6–2.2 eV. The former does not shift appreciably with varying annealing time and initial film composition. It is related to radiative recombination via defect states at the a-Si/SiOx interface. The maximum of the low-energy band shows a gradual red shift with decreasing x and increasing annealing time, i.e., with increasing nanoparticle size. This is related to carrier recombination in amorphous Si nanoparticles. Investigations of thermal quenching of the PL confirm the last assumption.

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Room-temperature PL spectra of SiOx films with four different compositions annealed in an Ar atmosphere at 973 K for 60 min. The dash-dot spectrum was measured on a film with x = 1.15 annealed for 30 min at 523 K.