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

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 chemic...

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Bibliographic Details
Published in:Thin solid films 2013-10, Vol.545, p.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: Article
Language:English
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
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Summary: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.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2013.04.092