Investigation of metal-ferroelectric interfaces at micro and nanometric level (Investigarea interfeţelor metal- feroelectric la nivel micro şi nanometric) IFA-CEA cooperation program Presenting: Dr. Lucian Pintilie Project responsible from the Romanian part IFA-CEA symposium 20 of October 2011, Magurele 1

The main objective of the project will be to study the construction of the metal-ferroelectric interface and the dynamic of charge compensation in relation to polarization switching. The results will be compared to the results of the macroscopic electric measurements performed on standard metal- ferroelectric-metal (MFM) capacitors. Also, the metal-ferroelectric interface will be compared with the results reported for the free surface. Scope of the project Important milestones End of the 1 st year-deposition and characterization of epitaxial PZT films; conclusions regarding the charge compensation on the free surface End of the 2 nd year-formation of metal-PZT interface and characterization through surface/interace investigation techniques; charge compensation at the interface End of the 3 rd year-macroscopic-microscopic correlation 2

IFA-CEA symposium 20 of October 2011, Magurele 3 Teams and collaboration There is a common interest in the proposed topic. The responsible of the Romanian part has collaborated with Dr. Gweneal Le Rhun, member of the CEA team, during their workstages at MPI Halle, Germany. Dr. Pintilie was visiting scientists while dr. Le Rhun was a Humboldt fellow. A few common papers resulted from this collaboration (see the list below). The present project will help to develop the collaboration between the two teams to a new level. RO teamCEA team Project leader (Name) Dr. Pintilie LucianDr. LE RHUN Gwenaël Laboratory Institution Address Tel : Fax : Head of laboratory Laboratory Multifunctional Materials and Structures National Institute of Materials Physics Atomistilor 105bis, Magurele , Romania +40-(0) (0) Dr. Ionut Enculescu Grown of SRO layer on STO/Si substrates; grown of PZT/SRO on single crystal STO substrates; surface/interface investigation; electrical measurements with temperature; comparison with samples from France RF Components Laboratory CEA 17 rue des Martyrs, Grenoble Cedex 9, FRANCE +33-(0) (0) AID Marc Grown of STO on Si substrate, and of PZT on SRO/STO/Si; preliminary electrical characterization RO teamCEA team Dr. Lucian Pintilie Dr. Stancu Viorica (young researcher) Dr. Ioana Pintilie Dr. Cristian Mihail Teodorescu Drd. Cristina Dragoi (young researcher) Drd. Marius Husanu (young researcher) Drd. Lucian Trupina Dr. Gwenaël Le Rhun (young researcher) Dr. Emmanuel Defaÿ Shi YIN (young researcher)

IFA-CEA symposium 20 of October 2011, Magurele 4 Results: Romanian team AFM pictures of STO substrate (left), SRO film (middle) and PZT film (right) HR-TEM picture of the PZT-SRO-STO interfaces

IFA-CEA symposium 20 of October 2011, Magurele 5 The stability of the polarization on the bare surface Local piezoelectric hysteresis

IFA-CEA symposium 20 of October 2011, Magurele 6 NivelASFPozitie niveluri energetice (eV) in diferiti compusi PbTiZrPbOPbO 2 TiO 2 ZrO 2 PbTiO 3 PbZrO 3 Au O 1s ?- Ti 2p Zr 3d ?- Pb 4f Au 4f Ipoteza 1: tot O Ipoteza 2: fara O (c4) Ipoteza 3: fara O (c3 + c4) Compone nte comp. at. % total at. % comp. at. % total at. % comp. at. % total at. % O 1s (1) O 1s (2) O 1s (3) fara [20.15] O 1s (4)14.59 fara [17.09] fara [20.53] Ti 2p (1) Ti 2p (2) Ti 2p (3) Zr 3d (1) Zr 3d (2) Zr 3d (3) Pb 4f (1) Pb 4f (2) Pb 4f (3) Suma Pb 1.31 Ti 0.75 Zr 0.25 O 4.62 Pb 1.31 Ti 0.75 Zr 0.25 O 3.61 Pb 1.31 Ti 0.75 Zr 0.25 O 2.61 Results of XPS analysis: -surface is depleted in oxygen -some PbCO3 and PbO forms at the surface

IFA-CEA symposium 20 of October 2011, Magurele 7 Changes observed after treatment in oxygen plasma Behavior of short-circuit current for different electrodes

IFA-CEA symposium 20 of October 2011, Magurele 8 PFM studies on PZT52/48 films deposited in France, above the SRO film deposited in Romania by PLD

IFA-CEA symposium 20 of October 2011, Magurele 9 Results: French team Figure 1: RHEED images at the end of STO deposition Figure 2: 2θ/ω scan on PZT deposited on STO/Si Hysteresis and C-V curves for PZT52/48 films deposited by sol-gel in France, above the SRO layer deposited by PLD in Romania

IFA-CEA symposium 20 of October 2011, Magurele 10 Benefits of the collaboration Romanian team: - Has learned that STO can be epitaxially grown on Si - Has the opportunity to compare the results obtained on epitaxial PZT films grown by sol-gel with those of the films grown by PLD French team: -Can grow the PZT films on SRO layers, thus can develop metal- ferroelectric-metal structures - Has the opportunity to compare the results obtained on epitaxial PZT films grown by sol-gel with those of the films grown by PLD Observation: Due to some organizational problems on the French side, which generated delays in getting the financial support, it was not possible to exchange visits in the first year of the project.

IFA-CEA symposium 20 of October 2011, Magurele 11 Perspectives for the next years Foreseen common activities: - Finalizing the comparison of surface properties and PFM results on sol-gel and PLD deposited PZT52/48 films both on SRO/STO/Si and SRO/STO(sc) substrates -Testing common metals used in microelectronics (Cu, Au, Al) as electrodes and compare the results on sol-gel and PLD deposited films - Studying the electrode-PZT interface by various methods, with emphasis on PFM and PLD Publications: L. Pintilie, C. Dragoi, and I. Pintilie, “Interface controlled photovoltaic effect in epitaxial Pb(Zr,Ti)O3 films with tetragonal structure”, JOURNAL OF APPLIED PHYSICS 110, (2011) L. Pintilie, C. Dragoi, V. Stancu, G. Ibanescu, I. Pintilie, “Effect of microstructure and electrode interface on the hysteretic behavior of ferroelectric Pb(Zr,Ti)O3 thin films”, sent to JOURNAL OF PHYSICSD: APPLIED PHYSICS N.G. Gheorghe, G.A. Lungu, C.M. Teodorescu, I. Pintilie, L. Trupina, C. Dragoi, “Photoelectron spectroscopy studies of pulsed laser deposited Pb(Zr,Ti)O 3-δ single crystal films”, sent to PHYSICA STATUS SOLIDI- RAPID RESEARCH LETTERS