Temporal Stabilization of Porous Silicon Through Oxidation

It was also observed that the creation of nonradiative dangling bonds inCTeases the cioss-condnc-tivity of the PSi-Si structures. The appearance in porous silicon of a large number of defects, which are the consequence of broken silicon bonds on the surface of nanostructures, is registered by the method of electron paramagnetic resonance (Meyer et al. 1993). 

2 Temporal Stabilization of Porous Silicon Through Oxidation 

In the previous section it was concluded that, due to strong temporal instability of PSi properties, the design of the methods acceptable for their stabilization is a task of great importance for development of all types of gas sensors (Korotcenkov and Cho 2010a). After much research it was established that the oxidation is one of the most effective methods for stabilization of the properties of PSi, including optical, photoluminescence and sensing characteristics (Canhman 1997 GeUoz etal. 2005 Pirasteh et al. 2006). 

Source Reprinted with permission from Korotcenkov and Cho (2010b). Copyright 2010 Taylor and Frances 

Research has shown that for obtaining dense SiO from a PSi layer, the dimensions of the pores should balance the volume expansion during the thermal oxidation by a factor of 2.27 and by a pore wall thin enough to be fully oxidized. It was found that this condition can be achieved when the PSi porosity is in the range 55-90 % (Maccagnani et al. 1998). A layer of lower porosity will never be fully oxidized, while an increased porosity would give a very fragile macro-PSi structure and consequently a very weak porous SiO.  

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