Optical properties of SiO2/nanocrystalline Si multilayers studied using spectroscopic ellipsometry

• Published in: Thin solid films 2005-04, Vol.476 (1), p.196-200
• Main Authors: LEE, Kang-Ju, KANG, Tae-Dong, LEE, Hosun, SEUNG HUI HONG, CHOI, Suk-Ho, SEONG, Tae-Yeon, KYUNG JOONG KIM, DAE WON MOON
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Physics; Semiconductors; Visible and ultraviolet spectra
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2004.09.037

Using variable--angle spectroscopic ellipsometry, we measure the pseudo--dielectric functions of as--deposited and annealed SiO2 /SiOx multilayers. The SiO2(2 nm)/SiOx(2 nm) multilayers are prepared under various deposition temperatures by ion beam sputtering. Annealing at temperatures above 1100 deg C leads to the formation of Si nanocrystals (nc--Si) in the SiOx layer of multilayers. Transmission electron microscopy images clearly demonstrate the existence of nc--Si. We assume a Tauc--Lorentz lineshape for the dielectric function of nc--Si, and use an effective medium approximation for SiO2/nc--Si multilayers as a mixture of nc--Si and SiO2. We successfully estimate the dielectric function of nc--Si and its volume fraction. We find that the volume fraction of nc--Si decreases after annealing, with increasing x in as--deposited SiOx layer. This result is compared to expected nc--Si volume fraction, which is estimated from the stoichiometry of SiOx.