IR absorption analysis of oxidation behaviors of nano-composite phases with β-FeSi₂nanocrystals and Si

Abstract

We have investigated oxidation behaviors of nano-composite phase with -FeSi2 nanocrystals (-NCs) and Si on Si substrates. IR absorption measurements revealed that only oxidation of Si into SiO2 proceeded in the nano-composite phase. This fact is very important for realization of a novel composite phase with -NCs and SiO2, which may contribute to enhancement of light emission and to prevent a large thermal quenching of light emission observed in the composite phase with -NCs and Si.

Enhancement of photoluminescence from nanocrystal β-FeSi2/SiO2 composite and relaxation of thermal quenching

“…The formation of β-NC=Si composites was confirmed by far-infrared absorption measurements, because a β-NC=Si composite has its specific phonon spectrum different from those of β-FeSi 2 precipitates and thin films. 33) In our preliminary work, 45) we have found the selective oxidation of Si in β-NC=Si composites on the basis of midand far-IR absorption spectra and the growth of only SiO 2 during oxidation at 900 °C in air. The β-NC=Si composites synthesized by annealing at 800 °C for 2 h were employed as a starting material for oxidation.…”

“…The composite with β-FeSi 2 =SiO 2 heterojunctions is a promising candidate that may be synthesized directly from β-FeSi 2 =Si composites by the selective oxidation of Si. 45) In the β-FeSi 2 =SiO 2 heterojunctions, the ΔE v of ∼3.58 eV can be expected and may be sufficient to confine holes in β-FeSi 2 wells at RT. It has already been reported that β-FeSi 2 nanocrystals (β-NC) embedded in SiO 2 (i.e., β-NC=SiO 2 composite) can be synthesized by the sample oxidation of β-FeSi 2 =Si heterojunctions in dry air at 900 °C and evident PL was successfully observed at 250 K. 46) Moreover, in SiO 2 growth during the oxidation of β-FeSi 2 =Si, no structural or quantitative changes in β-NCs were found by infrared absorption measurements, and it was pointed out that Si was selectively oxidized.…”

Photoluminescence property of nano-composite phases of β-FeSi₂ nanocrystals embedded in SiO₂

“…From an electronic view point, the formation of SiO2 at the surface is very important to make the radiative recombination between electrons and holes larger, because SiO2 has a larger band-gap and can make larger band offsets (Ec, Ev) with -FeSi2 than Si. FTIR study of oxidation of nano-composite phase revealed that only Si phase can be oxidized into SiO2 and promising nano-composite of -NCs embedded in SiO2 [3]. In this study, photoluminescence property of nano-composite of -NCs embedded in SiO2 (-NCs/SiO2) was investigated toward possible light emission near room temperature.…”