Stabilizing Light Emission of Porous Silicon by In-situ Treatment

Abstract

The photoluminescence of porous silicon prepared by etching in an aqueous solution of hydrofluoric acid mixed with phosphoric and that with nitric acid were red and orange, respectively. The optical characteristics were stable under laser illumination or when stored in air for the aging test. For etching in an aqueous hydrofluoric acid/phosphoric acid electrolyte, the stability is attributed to the existence of Si-P and P-O-Si bonds formed on the porous silicon surface. For etching in an aqueous hydrofluoric acid/nitric acid electrolyte, it is attributed to more Si-O bonds formed on the porous silicon surface.

Silicon Porosification: State of the Art

“…12,41,369 This set contains everything not included in the list above, but so far they had little practical significance. Examples, which can be found in the literature, include H 3 PO 4 with a small amount of HF, 38,370 absolutely water free organic electrolytes, 15 and diluted HF with CrO 4 −2 . 371 It is important to mention here that all of the above mentioned electrolytes are extremely dangerous liquids and must be used and disposed of with care.…”

“…The effect of "aging" on both the composition and structure of porous Si are now well documented. 88,114,[517][518][519][520] Changes in material properties, such as electrical resistivity and strain, and optical properties, such as Downloaded by [Stanford University Libraries] at 04: 49 11 October 2012 refractive index and photoluminescence, accompany the ageing processl (see Table 11). According to Canham, 527 the "aging" of porous silicon results from the reaction of the material with its environment: the surrounding ambient and sometimes the containment vessel, usually via oxidation of PSi internal surface.…”

How to Improve the Performance of Porous Silicon‐Based Gas and Vapor Sensors? Approaches and Achievements

“…For example, it is well known that at room temperature and an environment of about 7 nm layer of SiO 2 can be formed over time on the surface of silicon. Oxidation, as reported by Bjorkqvist et al, is a very slow process at room temperature and, thus, leads to constant changes in the composition, structure, and physical parameters of PSi layers . Consequently, the properties of highly porous devices based on silicon and PSi, such as electrical resistivity, mechanical strain, and optical properties, such as RI and PL, are not stable over time, especially in the initial stages of operation after manufacture (see Figure ).…”

Thermal Properties of Porous Silicon

“…As stated previously, PSi slowly reacts with the ambient air and consequently its chemical composition and its properties evolve continuously with storage time. The effects of "aging" on both the composition and structure of PSi are now well-documented (Sham et al 1992;Xie et al 1992;Zhu et al 1992;Chelyadinsky et al 1997;Dolino and Bellet 1997;Lee and Tu 2007;Sorokin et al 2010). For example, as early as 1965 Beckmann (1965) had recorded the pronounced "ageing" (slow oxidation) of films that were stored in ambient air for prolonged periods.…”