Silicon rich oxide (SRO) films with different silicon excess were deposited by low pressure chemical vapor deposition (LPCVD) using SiH4 and N2O as the reactant gasses. A set of SRO films was implanted with silicon ions (SI-SRO). After thermal annealing, SRO and SI-SRO films with low Si excess showed a strong visible photoluminescence (PL) in the 1.4-2.1 eV range, characteristic of silicon nanocrystals (Si-nc's) formation. For SRO layers, a redshift of the PL peak was only observed by increasing the silicon excess from 4 to 5.1 at. %, no redshift took place when the silicon excess was 12.7 at. %. The SI-SRO films exhibited a similar behaviour. For implanted and non implanted samples, transmission electron microscopy analysis only showed silicon clusters when the silicon excess was higher than 5 at. %. It has been observed that the Si-clusters size was larger as the silicon excess increased and that the Si-clusters density increased when the SRO films were implanted. Therefore, a stronger PL response was observed in the SI-SRO films. The structural and optical properties of SRO and SI-SRO films have been related, suggesting that the emission could be associated to Si-clusters/defects interaction.
- Silicon clusters
- Silicon rich oxide