Stain etch films, porous silicon

Yamauchi Y, Sakurai T, Hirohata Y, Hino T, Nishikawa M (2002) Blue shift of photoluminescence spectrum of porous silicon by helium ion irradiation. Vacuum 66(3-4) 415—418 Zanoni R, Righini G, Mattogno G, Schirone L, Sotgiu G, Rallo F (1999) X-ray photoelectron spectroscopy characterization of stain-etched luminescent porous silicon films. J Lumin 80 159-162... 

The formation of porous layers in silicon by chemical etching in HF/HNO3 solutions was first reported at about the same time as electrochemical etching [101-104]. These so-called stain etch films are characterized by rough or porous surfaces, typically < 500 A in thickness. Recent work has shown that these stain etch films exhibit strong visible photoluminescence, similar to the emission observed from electrochemically etched porous silicon layers. 

D. Dimova-Malinovska, M. Sendova-Vassileva, N. Tzenov, and M. Kamenova, Preparation of thin porous silicon by stain etching. Thin Solid Films 297, 9, 1997. 

The very first studies of mesoporous silicon noted the different colors of anodized and so-called stain films (Uhlir 1956 Turner 1958 Archer 1960). Uhlir referred to his surfaces as having a matte black, brown or red deposif (Uhlir 1956). Turner commented that several orders of interference colors can be seen as the film thickens (Turner 1958). The first use of such colored silicon in the late 1950s was in p-n junction delineation (lies and Coppen 1958 Whoriskey 1958 Robbins 1962). Porous silicon, with its lower refractive index than solid silicon, induces optical interference effects as etched films on wafers. A colorimetric analysis for layer thicknesses below 500 nm, at quantified porosities, showed that interference color directly related to the optical thickness of anodized singlelayer structures (Lazarouk et al. 1997). Figure 1 shows examples for stain-etched p + wafers. The visual color of a given layer can be further changed by plasmonic effects of deposited metal nanoparticles (Lublow et al. 2012) or through controlled oxidation of the silicon skeleton. 

Schirone L, Sotgiu G, Parisini A, Montecchi M (1997) Optical and morphological properties of stain-etched porous silicon films for anti-reflection coatings of photovoltaic devices. Sohd State Phenom 54 59... 

Xu YK, Adachi S (2008) Properties of light-emitting porous silicon formed by stain etching in HF/KIO3 solution under light illumination. J Appl Phys 103 103512-1-6 Yamamoto N, Takai H (2000) Visible luminescenee from photo-chemically etched sihcon. Thin Solid Films 359 184-187... 

Fig. 1 Four Si(lOO) substrates stain etched for different times to produce homogeneous smooth films of different depths, hence different colors caused by thin film interference in the porous silicon layers...

Diaz-Herrera B, Jimenez-Rodriguez E, Gonzalez-Diaz B, Montesdeoca-Santana A, Velazquez JJ, Guerrero-Lemus R (2011) Combined up conversion, down conversion and down shifting photo-luminescence of low cost erbium-ytterbium co-doped porous silicon produced by stain etching. Thin Solid Films 519 6110-6114... 

Kelly MT, Chun JKM, Bocarsly AB (1994) High efficiency chemical etchant for the formation of luminescent porous silicon. Appl Phys Lett 64 1693-1695 Kidder JN Jr, Williams PS, Pearsall TP, Schwartz DT, Nosho BZ (1992) Comparison of light emission from stain-etch and anodic-etch silicon films. Appl Phys Lett 61 2896-2898 Koker L, Wellner A, Sherratt PAJ, Neuendorf R, Kolasinski KW (2002) Laser-assisted formation of porous silicon in diverse fluoride solutions hexafluorosilicate deposition. J Phys Chem B 106 4424-4431... 

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