Please cite this article in press as: M.A. Hus ¸ anu, et al., Photoelectron spectroscopy and spectro-microscopy of Pb(Zr,Ti)O 3 (1 1 1) thin layers: Imaging ferroelectric domains with binding energy contrast, Appl. Surf. Sci. (2015), http://dx.doi.org/10.1016/j.apsusc.2015.01.153 Applied Surface Science xxx (2015) xxx–xxx Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc Photoelectron spectroscopy and spectro-microscopy of Pb(Zr,Ti)O 3 (1 1 1) thin layers: Imaging ferroelectric domains with binding energy contrast Marius A. Hus ¸ anu a , Dana G. Popescu a , Cristian A. Tache a , Nicoleta G. Apostol a,b , Alexei Barinov b , Silvano Lizzit b , Paolo Lacovig b , Cristian M. Teodorescu a,∗ a National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele-Ilfov, Romania b Elettra Sincrotrone Trieste, S.S. 14 – km 163,5, Area Science Park, 34169 Basovizza-Trieste, Italy a r t i c l e i n f o Article history: Received 14 November 2014 Received in revised form 18 January 2015 Accepted 20 January 2015 Keywords: Ferroelectrics X-ray photoelectron spectroscopy Photoelectron spectro-microscopy Band bending Depolarization Metal segregation a b s t r a c t The ability of photoelectron spectro-microscopy with sub-micrometer lateral resolution to identify fer- roelectric domains by analysis of surface band bendings is demonstrated on lead zirco-titanate PZT(1 1 1) thin films grown by pulsed laser deposition. Conventional synchrotron radiation X-ray photoelectron spectroscopy allowed one to derive the surface composition of the sample and evidenced shifts toward higher binding energy when the sample is subject to intense soft X-ray beam. A basic model is developed which supposes that photogenerated carriers reduce the depolarization field, yielding a lower torque applied to the ferroelectric polarization. As a consequence, the out-of-plane component of the polariza- tion increases. Domain migration during irradiation with soft X-ray is inferred from the relative amplitude of the components with different binding energy. When the flux density of soft X-ray is on the order of 10 11 photons/(s m 2 ), metal Pb clusters are formed at the surface on areas with the out-of-plane component of the polarization pointing outwards only. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Ferroelectrics have been intensively investigated in the past in view of their applications in microelectronics [1,2], and amongst the ferroelectric used nowadays, lead zirco-titanate (PZT) is prob- ably the most investigated [2], owing also to its high Curie temperature and remarkable polarization, sometimes exceeding 1 ◦ C/m 2 [3]. However, the depolarization of these materials and their temporal instability is still an issue, therefore for non-volatile memories still the floated gate concept is the most used nowadays. In turn, recent years brought intensive studies of ferroelectrics in view of their applications in catalysis [4], photocatalysis [5] and photovoltaics [6]. The interest of using ferroelectrics in chemistry and photochemistry is easy to understand, since the presence of an internal electric field yields to an efficient electron–hole sepa- ration with no need for a rectifying contact; also, the surface band bendings promote ferroelectric surfaces as active entities for both oxidation and reduction processes [7]. Moreover, it is well known that electron–hole recombination is the basic issue of the efficiency ∗ Corresponding author. Tel.: +40 213690170. E-mail address: teodorescu@infim.ro (C.M. Teodorescu). of any photocatalyst. Molecular adsorption at ferroelectric surfaces was also found to be greatly influenced by the out-of-plane polar- ization state of the surface [8,9]. It is clear that efforts are needed to understand both the interaction between molecules and ferro- electric surfaces and also of the ferroelectric surfaces themselves, particularly in what concerns the effects of the depolarization fields [10] and of domain wall migration [3,11]. For the latter, high reso- lution transmission electron microscopy is the principle tool [3,10]. In turn, for catalysis and for molecular reactions at surfaces X- ray photoelectron spectroscopy (XPS) is amongst the widest used method [12]. The basic information that can be provided by XPS are the sample composition and the chemical compounds formed in a layer with thickness on the order of the inelastic mean free path (IMFP) of the photoelectrons, which ranges between 0.5 and 2 nm [12,13]. Taking into account the surface sensitivity of XPS, a new development was made during the last years on the ability of this technique to derive surface band bendings [14]. This method was extended to the case of free ferroelectric surfaces [9,15–17] and of metals deposited on these surfaces [15,18–20], by taking into account the recent developments in the area of preparation of single crystal epitaxial ferroelectric layers by modern techniques, such as pulsed laser deposition (PLD) [3,9,10,13,16–20]. The basic idea behind such determination is the model where a compensated http://dx.doi.org/10.1016/j.apsusc.2015.01.153 0169-4332/© 2015 Elsevier B.V. All rights reserved.