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Abstract
Effects of vacuum and ambient thermal annealing and ageing on the photoluminescence (PL) spectra of porous silicon (po-Si) have been investigated. Isochronal anneals up to 300°C were done and PL spectra were recorded and compared to the un-annealed specimens. Minimal changes are induced for anneals below approximately 125°C; however, significant reduction in PL intensity occurs following anneals at T ≥ 200°C. Deconvolution of the PL spectra into five distinct Gaussian bands reveals that at least two of the bands are attributable to non-quantum confinement mechanisms. Specifically, bands appearing at 1.58 and 1.78 eV are ascribed to non-bridging oxygen hole related defects. Recovery of PL intensity following thermal annealing occurs over a period of several days at a rate that is dependent upon annealing temperature and environment. Passivation of Si dangling bonds on the po-Si surface via effusion of hydrogen and incorporation of oxygen is responsible for the observed variations in PL intensity.
Acknowledgements
This research was supported in part by the Laboratory's Directed Research and Development Program and in part by the US Department of Energy, Office of Basic Energy Sciences.