Optical properties and electronic band lineup on Si of amorphous zirconium modified Bi2Zn2/3Nb4/3O7 thin films

Abstract

We have investigated optical and band alignment properties of pulsed laser deposited amorphous thin films of bismuth based monoclinic pyrochlore Bi2Zn2/3−x/3Nb4/3−2x/3ZrxO7 (Zr–BZN) where x=0.4 on quartz and silicon substrates, respectively. The optical parameters, such as complex refractive index (n−jk), energy bandgap (Eg), complex dielectric function (ε′-jε″), and complex conductivity (σ′-jσ″) and associated dispersion parameters were estimated from the UV–Visible transmission spectra. The analysis of refractive index dispersion confirmed the Wemple–DiDomenico single-effective-oscillator model for the direct inter-band transition. The valence band of Zr–BZN is found to be ∼0.1eV above that of silicon. The numerical values for conduction band offset ΔEC on silicon and optical bandgap Eg were estimated to be ∼2.46eV and ∼3.46eV, respectively for Zr–BZN samples. We determined a complete electron band offset dominated type II staggered band lineup of this high-k dielectric/semiconductor heterostructure, where a straight forward spatial confinement of electrons and holes is facilitated. These important results can play critical role and provide key insight for the practical applications of Zr–BZN material, especially in CMOS (complementary metal–oxide–semiconductor) logic and memory devices.