Photoluminescence mechanisms in porous oxidized Si were investigated. We observed marked enhancement in the photoluminescence intensity of porous Si when it was oxidized at high temperatures from 800 to 900thinsp;deg;C in dry oxygen. The photoluminescence decay of both ashyphen;prepared and dryhyphen;oxidized porous Si was intrinsically nonexponential. As reported by other groups, the photoluminescence lifetime, defined as 1/etimes, decreased as the emission energy increased for ashyphen;prepared samples, and were from 60 to 200 mgr;s. The spread in lifetimes is usually interpreted in terms of the size distribution of Si microcrystals, and the long lifetime on a microsecond time scale is explained by a carrierrsquo;s tunneling model. The photoluminescence lifetime for dryhyphen;oxidized porous Si, however, did not depend on the emission energy and was about 100 mgr;s. The result clearly shows the presence of radiative recombination processes via luminescence centers, especially in dryhyphen;oxidized porous Si.
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