Band bending in Au/Pb(Zr,Ti)O3 investigated by X-ray photoelectron spectroscopy: Dependence on the initial state of the film

• Published in: Thin solid films Vol. 545; pp. 13 - 21
• Main Authors: Apostol, Nicoleta G., Stoflea, Laura E., Lungu, George A., Tanase, Liviu C., Chirila, Cristina, Frunza, Ligia, Pintilie, Lucian, Teodorescu, Cristian M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 31.10.2013; Elsevier
• Subjects: Band bending; Bending; Charge; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Deposition; Dielectric thin films; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Ferroelectrics; Formations; Gold; Lead zirconate titanates; Physics; Polarization; Schottky barrier; Surface charge; Surface double layers, schottky barriers, and work functions; Titanium; X-ray photoelectron spectroscopy; Surface charge; Band bending; Ferroelectrics; X-ray photoelectron spectroscopy; Schottky barrier; Buffer layer; Work functions; Schottky barriers; PZT; Core levels; Thin films; Interfaces; Ferroelectric materials; Binding energy; Bending; Ferroelectric thin films; X-ray photoelectron spectra
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.04.092

This work presents a systematic investigation by X-ray photoelectron spectroscopy of the mechanisms of interface formation and band bending for Au/Pb(Zr,Ti)O3 (PZT) layers grown on SrTiO3(001) with a SrRuO3 buffer layer, as function on the initial state of the PZT surface. After isolating the chemical effects, such as the formation of metal Pb at some surfaces, the evolution of the core levels with Au deposition allows one to simultaneously investigate the Schottky barrier formation and the built-in potential effects (charging induced by the static ferroelectric polarization). Areas of the sample with outwards P(+) and no polarization perpendicular to the surface P(0) are identified for all samples. Only the freshly prepared sample exhibited inward polarization areas P(−). The built-in potential is on the order of 0.9eV, while the Schottky band bending ranges from 0.2 to 0.6eV towards lower absolute energies, therefore indicating that the work function of PZT exceeds that of Au deposited. We report also a chemically differentiate value of the built-in potential, manifested by a preferential distribution of the charge accumulated at the surface on Ti and O atoms. The O 1s and Ti 2p core levels manifest quite strong variations with the Au thickness for freshly prepared samples, resulting in shifts on the order of 2eV towards lower binding energies. Au deposited on areas with an outward polarization is positively charged by the same potential as atoms from the PZT film (0.8–0.9eV), whereas Au deposited on areas with an inward polarization forms a continuous grounded layer, which progressively pumps the accumulated charge and removes the polarization of these areas. •Assessment by XPS of areas with different ferroelectric polarization.•Inwards polarized areas identified only on freshly prepared substrates.•Follow-up of the Schottky barrier formed at Au/PZT(001) interfaces.•Inwards polarized areas exhibit higher binding energy shifts with Au deposition.•The depolarising charge is located preferentially on titanium and oxygen.