In Situ Formation of Nanoporous Silicon on a Silicon Wafer via the Magnesiothermic Reduction Reaction (MRR) of Diatomaceous Earth

Abstract

Successful direct route production of silicon nanostructures from diatomaceous earth (DE) on a single crystalline silicon wafer via the magnesiothermic reduction reaction is reported. The formed porous coating of 6 µm overall thickness contains silicon as the majority phase along with minor traces of Mg, as evident from SEM-EDS and the Focused Ion Beam (FIB) analysis. Raman peaks of silicon at 519 cm−1 and 925 cm−1 were found in both the film and wafer substrate, and significant intensity variation was observed, consistent with the SEM observation of the directly formed silicon nanoflake layer. Microstructural analysis of the flakes reveals the presence of pores and cavities partially retained from the precursor diatomite powder. A considerable reduction in surface reflectivity was observed for the silicon nanoflakes, from 45% for silicon wafer to below 15%. The results open possibilities for producing nanostructured silicon with a vast range of functionalities.

On the diatomite-based nanostructure-preserving material synthesis for energy applications

“…The use of an inorganic salt for scavenging excess heat produced from the MRR of diatomite was reported by Luo et al 182 In their work, the use of NaCl resulted in a product silicon with cylindrical architectural features retained from the precursor diatomite. This particular trend has been reported in a number of studies, 36,112,[183][184][185] suggesting an effective way to control the overall temperature in the MRR. This high purity silicon had a rough surface occupied with ultrane Si particles (F10 nm).…”

“…Following this great lead, a number of works centered on diatomite made use of inorganic salts to complement the already favored MRR process. 36,112,[182][183][184][185] In all these reports, the reductant used was magnesium. The ready availability, low cost, low toxicity and low melting temperature make magnesium the most preferred reductant among the lot.…”

“…To obtain pure silicon aer the MRR, HCl is frequently used to dissolve MgO and further rinsing with deionized water. In quite a number of works, 36,112,182,183 HF was used following HCl washing to dissolve all unreacted silica as a way to obtain pure Si. In the work of Shen et al 186 only HCl was reported, suggesting an eco-friendlier approach but also accounting for the traces of unreacted silica in the porous silicon powder as detected by Raman spectroscopy.…”

FEM exploration of the potential of silica diatom frustules for vibrational MEMS applications

“…To confirm the reliability of our results, we used the analytical results of Shang [31]. Using the Naghdi-Reissner shell theory and Legendre functions, an analytical solution was obtained for vibration frequencies of sphericalcylindrical shells that was expressed in the form: More detailed matching of numerically derived correlations to analytical solutions is unrealistic, for several reasons:…”

“…: 3 / ;.It can be seen from above that the principal leading terms/ 0 are captured correctly. The term denoted by Shang[31] as = ( , ) that accounts for morphological details of the shell, in our notation is given by 7 ;, benefitting from the more precise and specific identification of dependence on t and d.…”