Praseodymium silicate formed by postdeposition high-temperature annealing

Abstract

Praseodymium silicate (Pr silicate) has been synthesized by molecular-beam deposition of Pr2O3 layers on Si(111) substrates and subsequent high-temperature postdeposition annealing at 1000 °C. This thermal treatment drastically changes the film texture from the crystalline Pr2O3 epitaxially grown on Si, into Pr silicate with completely amorphized structures, resulting from intermixing of Si from the substrate. It was found that the electrical characteristics of Pr silicate were critically dependent on the quality of the as-deposited Pr2O3 films. A typical dielectric constant and a leakage current density of Pr silicate grown under an optimal condition were, respectively, 19.7 and 3×10−9Acm−2 at +1 V relative to the flatband voltage for an equivalent oxide thickness of 1.9 nm. Using x-ray photoelectron spectroscopy, a valence-band offset at the Pr-silicate/Si(111) interface of 2.75 eV and a band gap of 6.50 eV were obtained. The large band gap and the highly symmetric band alignment account for the observed low leakage current density.