Comparative Analysis of the Effect of Immersion of Porous Silicon in Aqueous Solutions of Li and Fe Salts on the Stability, Peak Position and Intensity of its Photoluminescence

Abstract

In the process of comparative studies of immersing layers of porous silicon (PS) in aqueous solutions of LiBr and Fe (NO3)3 with subsequent long-term storage up to 150 days, it is established that there exists: (1) the range of concentrations of LiBr (S/2 - S/4) and Fe (NO3)3 (0.2 M), which provide the maximum increase in the intensity of PL; (2) at low concentrations of both salts, a blue shift of the PL peaks and an increase in their intensity are observed during the long-term storage, which is associated with a decrease in the size of the NC in the PS and the influence of silicon bonds with lithium or iron ions; (3) full protection of the PS layer is observed in case of immersion in Fe (NO3)3 with a concentration of 0.7M - 0.8M.

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

“…3 a), but appears in the working m/por-Si sample with an immersion time of 20 minutes, which indicates the formation of Si-O-Li bonds (Fig. 3 (b, c)), as in [6]. and Si-OH, 3400 cm -1 (f).…”

“…Silicon samples were anodized under the following conditions: current density of 10 mA/cm 2 and duration of 5 minutes in a solution of HF:CH3OH = 2:1. This ensured the formation of the m/por-Si layer with a porosity of about 55% and a thickness of 4 μm [6]. After anodizing, each sample was washed in deionized water, dried in a stream of dry nitrogen at room temperature.…”

“…After immersion in a LiBr aqueous solution, all three samples of the S/3 series were dried in a stream of dry nitrogen at room temperature without additional rinsing in deionized water. The equipment and methods for measuring the PL and IR spectra are described in [6]. The PL spectra and transmission spectra were recorded at T = 20 °C for 171-200 days.…”

“…The second problem is the change in the properties of por-Si during long-term storage in atmospheric conditions due to oxidation, which affects the stability of future sensor devices. One of the possibilities for preserving por-Si layers is their processing in salt solutions, for example, lithium bromide (LiBr) [5,6]. Studies have shown that for mesoporous Si (m/por-Si), in contrast to nanoporous Si [7], photoluminescence (PL) intensity increases with storage time, but a detailed analysis of the effect of immersion in an aqueous LiBr solution on the intensity has not been carried out.…”

“…In this work, we studied the effect of the storage duration of m/por-Si layers treated by immersion with various durations (5, 10, and 20 minutes) in an aqueous LiBr solution with the previously established optimal concentration [6], and etalon m/por-Si sample on the PL intensity and changes in the intensity of absorption peaks in the infrared (IR) spectrum on various siliconhydrogen, silicon-oxygen and silicon-hydroxyl groups.…”