Photoluminescence property of nano-composite phases of β-FeSi₂nanocrystals embedded in SiO₂

Abstract

We have investigated photoluminescence (PL) behaviors of nano-composite phase of -NCs embedded in SiO2 (-NCs/SiO2). The inhomogeneous spectra consisting of the A, B and C emission bands were observed. PL enhancement also was confirmed in comparison with -NCs/Si. Under high pumping rate, we observed PL spectra near room temperatures (~270 K). This fact means that oxidation of the nano-composite phase can contribute to reduction of thermal quenching, which may come from increase of band offsets around NCs. .

Analysis of oxidation behavior in nanocrystal β-FeSi2/Si composites by rutherford backscattering spectrometry and computation of diffusion flux

“…The diffusion fluxes of Si and O and their time dependence were computed. [3]. This result can be understood from a big difference in amount of diffusion fluxes between Si and O atoms as shown in Figs.3 (a)-(d).…”

“…One of candidates is a -FeSi2/SiO2 heterojunction, which may be easy to synthesize from -FeSi2/Si heterojunctions by sample oxidation. Nakamura et al have reported synthesis of nanocrystal -FeSi2 (NC-) embedded in SiO2 by using oxidation of samples in air, and they succeeded in observation of evident photoluminescence at 250 K [3]. Moreover, Morita et al [4] have reported time dependent growth of SiO2 in oxidation of -FeSi2/Si, and they found no structural and quantitative changes of NC- by using infrared absorption (IRA) measurements, and pointed that selective oxidation took place in the sample.…”

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

“…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. Such a selective oxidation is valuable for the synthesis of β-NC=SiO 2 composites from β-FeSi 2 =Si heterojunctions, and band offsets sufficiently large to confine electrons and holes in the well even above RT can be realized.…”

Photoluminescence enhancement of β-FeSi₂ nanocrystals controlled by transport of holes in Cu-doped n-type Si substrates

“…In the nano-composite in Si, we can not expect the valence band offset between -NCs and Si enough to make sufficient confinement of holes in -NCs near room temperature. Replacing Si with SiO2 has contributed to make both band offsets larger and thermal quenching (damping) of light emission smaller [1]. However, such a replacement may be unfavorable since Si substrates embedding -NCs is a crucial material for considerable applications.…”