a b s t r a c tWe have investigated optical and band alignment properties of pulsed laser deposited amorphous thin films of bismuth based monoclinic pyrochlore Bi 2 Zn 2/3Àx/3 Nb 4/3À2x/3 Zr x O 7 (Zr-BZN) where x = 0.4 on quartz and silicon substrates, respectively. The optical parameters, such as complex refractive index (n À jk), energy bandgap (E g ), complex dielectric function (e 0 À je 00 ), and complex conductivity (r 0 À jr 00 ) 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 $0.1 eV above that of silicon. The numerical values for conduction band offset DE C on silicon and optical bandgap E g were estimated to be $2.46 eV and $3.46 eV, 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.