Relationship between the Photoluminescence Spectra and IR Spectroscopy of Mesoporous Silicon Samples during Long-Term Storage: The Effect of Immersion in an Aqueous Fe(NO3)3 Solutions

The article provides a comparative analysis of changes in the PL spectra and infrared spectroscopy (IR) with reference and immersion samples of mesoporous silicon during long-term storage in air at room temperature. Immersion was carried out in an aqueous solution of iron nitrate (Fe (NO3)3) with a concentration of 0.2 M and 0.5 M with three times: 5, 10 and 20 minutes. An analysis of the FIR data for etalon and immersion samples showed a number of features found during long-term storage of mesoporous silicon: (1) a sharp decrease in the density of hydride bonds; (2) the polynomial nature of the growth of O3-SiH and Si-OH bonds saturating dangling bonds; and (3) the polynomial growth of silicon dioxide with the formation of oxygen defects. It was found that after immersion in a solution of 0.5 M Fe (NO3)3 for 10 minutes, a more intense increase in the PL in mesoporous silicon is observed while maintaining its nanostructure after 200 days of storage compared with the etalon sample, for which a weak quantum size confinement (QSC) is observed. The main mechanism of photoluminescence increase in mesoporous silicon during long-term storage is radiative recombination from oxygen defect levels, not from a QSC effect.