Porous silicon oxidation

M. Yamana, N. Kashiwazaki, A. Kinoshita, T. Nakano, M. Yamamoto, and C. W. Walton, Porous silicon oxide formation by the electrochemical treatment of a porous silicon layer, J. Electrochem. Soc. 137, 2925,1990. 

A. Prasad, S. Balakrishnan, S. K. Jain, and G. C. Jain, Porous silicon oxide anti-reflection coating for... 

Riikonen J, Salomaki M, van Wonderen J, Kemell M, Xu W, Korhonen O, Ritala M, MacMillan F, Salonen J, Lehto VP (2012) Surface chemistry, reactivity, and pore structure of porous silicon oxidized by various methods. Langmuir 28(28) 10573-10583. doi 10.1021/la301642w... 

Salonen J, Lehto VP, Bjorkqvist M, Laine E (1999a) A role of illumination during etching to porous silicon oxidation. Appl Phys Lett 75(6) 826-828... 

The temperature of the flame and the amount of gas generated during the nano-explosion were also experimentally investigated (Mason et al. 2009). The nominal maximum flame temperature for most porous silicon oxidizer systems is about 3,000 K, with the oxidant sulfur an exception where the flame temperature is only 1,600 K. The maximum gas production of the porous silicon explosives ranged from 650 cm /g of reactant for sulfur to 4,800 cm /g of reactant for NaC104. 

When porous silicon is immersed in an aqueous solution containing noble metal ions such as silver and copper, the metal is deposited on porous silicon. Oxidation of the porous silicon surface is confirmed by IR spectroscopy (Hilliard et al. 1994) and XPS spectroscopy (Jeske et al. 1995). In contrast, displacement reaction does not take place in deposition of less-noble metals such as nickel... 

Prasad A, Balakrishnan S, Jain SK et al (1982) Porous silicon oxide anti-reflection coating for solar cells. J Electron Chem Soc 129 596-599... 

Canham LT, Aston R (2003) Particles comprising porous and/or polycrystalline silicon or multilayer porous silicon oxide mirrors sunscreen agents. United States Patent Apphcation USP 20030170280Al... 

K. Nan, etal. Porous silicon oxide-PLGA composite microspheres for sustained ocular delivery of daunorubicin. Acta Biomater, 2014, http //dx.doi.Org/10.1016/j.actbio.2014.04.024. 

Many theories on the formation mechanisms of PS emerged since then. Beale et al.12 proposed that the material in the PS is depleted of carriers and the presence of a depletion layer is responsible for current localization at pore tips where the field is intensified. Smith et al.13-15 described the morphology of PS based on the hypothesis that the rate of pore growth is limited by diffusion of holes to the growing pore tip. Unagami16 postulated that the formation of PS is promoted by the deposition of a passive silicic acid on the pore walls resulting in the preferential dissolution at the pore tips. Alternatively, Parkhutik et al.17 suggested that a passive film composed of silicon fluoride and silicon oxide is between PS and silicon substrate and that the formation of PS is similar to that of porous alumina. 

To understand the electrochemical behavior of silicon, however, the formation and the properties of anodic oxides are important The formation of an anodic oxide on silicon electrodes in HF and HF-free electrolytes will therefore be discussed in detail in this chapter. The formation of native and chemical oxides is closely related to the electrochemical formation process and will be reviewed briefly. The anodic oxidation of porous silicon layers is closely related to the morphology and the luminescent properties of this material and is therefore discussed in Section 7.6. 

NHE OCP ONO OPS PCD PDS PL PLE PMMA PP PP PS PSG PSL PTFE PVC PVDF normal hydrogen electrode (= SHE) open circuit potential oxide-nitride-oxide dielectric oxidized porous silicon photoconductive decay photothermal displacement spectroscopy photoluminescence photoluminescence excitation spectroscopy polymethyl methacrylate passivation potential polypropylene porous silicon phosphosilicate glass porous silicon layer polytetrafluoroethylene polyvinyl chloride polyvinylidene fluoride... 

It is worth mentioning that the photooxidation of porous silicon behaves differently [49]. Indeed, ETIR spectra show that there is a tremendous increase in vsi o, without a correspondingly large loss of vsi H peak intensity. The decrease of the vsi H band is offset by an increase in the vosi—h band, resulting in no net loss of hydride species on the surface during the course of the photooxidation reaction. These data apparently suggest that oxidation does not result in the removal of H atoms, implying that Si—Si bonds are attacked directly. 

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