X-ray investigation of nanostructured stain-etched porous silicon

Abstract

The structure of porous silicon layers was accurately investigated by diverse x-ray methods. A series of samples with etching times varying from 1 to 10 min was produced by chemical etch using a HF/ HNO 3 -based solution assisted with NaNO 2 . The porosity determined from low-angle x-ray reflectivity spectra was found to fluctuate from 35% to 55% as the etch proceeds. Reciprocal space mapping around the ͑004͒ Si lattice point revealed that the Si crystallites are deformed due to a distribution of in-plane compressive strain caused by the neighboring pores, which leads to an expansion of the perpendicular lattice parameter. No signature of mosaicity was found. The perpendicular strain could be precisely determined by fitting the x-ray-diffraction spectra, measured in the triple-axis configuration, to a set of Voigt and Gaussian distributions. These strain distributions are certainly associated with the different population of crystallite sizes formed during the stain etching process. We were able here to determine the temporal evolution of the strain inside the nanostructured porous silicon.

Evolution of porous silicon crystal structure during storage in ambient air

“…The Gaussian fit makes it possible to reveal three sub-peaks which correspond to different PS layers. Similar rocking curves were observed in [4] for PS layer prepared by the stain-etch technique. The different parts of the PS layer after its air storage for 2660 hours can be seen in the TEM image of Fig.…”

Simple method for measuring the porosity, thickness and refractive index of porous silicon, based on the Fabry-Pérot interference spectrum

“…Figure 5 shows that the critical angles of the PSi samples are smaller than that found for the silicon substrate. That is explained because of the lower density of PSi layer (11) . Table 3 shows the critical angles values of the PSi samples.…”

Porous Silicon Formation by Stain Etching

“…Other sources of nitrogen oxo ions such as NaNO 2 (Archer 1960;Melnikov et al 2008;Kelly et al 1994;Campbell et al 1995;Vázsonyi et al 2001;Abramof et al 2006Abramof et al , 2007, NO 2 (Archer 1960;Yoshioka 1969), NOBF 4 (Kelly et al 1994;Safi et al 2002), or NOHSO 4 (Patzig et al 2007) have been used, but these are essentially running off of the same chemistry. A variation on standard HNO 3 -based stain etching was demonstrated by Chen et al (1996Chen et al ( , 2001Li et al 1999).…”