Investigation of metal-ferroelectric interfaces at micro and nanometric level

(Investigarea interfeţelor metal- feroelectric la nivel micro şi nanometric)

IFA-CEA cooperation programPresenting: Dr. Lucian Pintilie

Project responsible from the Romanian part

IFA-CEA symposium 20 of October 2011, Magurele 1

IFA-CEA symposium 20 of October 2011, Magurele

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 1st year-deposition and characterization of epitaxial PZT films; conclusions regarding the charge compensation on the free surface

End of the 2nd year-formation of metal-PZT interface and characterization through surface/interace investigation techniques; charge compensation at the interface

End of the 3rd 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 team CEA team

Project leader(Name)

Dr. Pintilie Lucian Dr. LE RHUN Gwenaël

LaboratoryInstitutionAddressTel :Fax :e-mail:Head of laboratory

Laboratory Multifunctional Materials and StructuresNational Institute of Materials PhysicsAtomistilor 105bis, Magurele 077125, Romania+40-(0)21-3690185+40-(0)21-3690177pintilie@infim.roDr. Ionut EnculescuGrown 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 CEA17 rue des Martyrs, 38054 Grenoble Cedex 9, FRANCE+33-(0)4-38784042+40-(0)4-38782434gwenael.le-rhun@cea.frAID MarcGrown of STO on Si substrate, and of PZT on SRO/STO/Si; preliminary electrical characterization

RO team CEA teamDr. Lucian PintilieDr. Stancu Viorica (young researcher)Dr. Ioana PintilieDr. Cristian Mihail TeodorescuDrd. 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

-3 -2 -1 0 1 2 3

-40

-20

0

20

40

d33

(pm

/V)

Vdc

Local piezoelectric hysteresis

IFA-CEA symposium 20 of October 2011, Magurele 6

Nivel ASF Pozitie niveluri energetice (eV) in diferiti compusiPb Ti Zr PbO PbO2 TiO2 ZrO2 PbTiO3 PbZrO3 Au

O 1s 0.66 - - - 529.3 529.0 530.0 529.9 529.9 ? -Ti 2p 1.8 - 454 - - - 459.0 - 458.6 - -Zr 3d 2.1 178.9 - - - 183.3 - ? -Pb 4f 6.7 136.9 - - 137.6 137.4 - - 139.0 138.5 -Au 4f 4.95 - - - - - - - - - 83.8

Ipoteza 1: tot OIpoteza 2: fara O

(c4)Ipoteza 3:

fara O (c3 + c4)Componente

comp. at. %

total at. %

comp. at. %

total at. %

comp. at. %

total at. %

O 1s (1) 1.01 66.65 1.18 60.97 1.42 53.11O 1s (2) 36.73 43.02 51.68

O 1s (3) 14.32 16.77fara

[20.15]

O 1s (4) 14.59fara

[17.09]fara

[20.53]Ti 2p (1) 1.88 10.87 2.21 12.73 2.66 15.29Ti 2p (2) 4.04 4.73 5.69Ti 2p (3) 4.9 5.78 6.95Zr 3d (1) 0.66 3.56 0.77 4.17 0.92 5.02Zr 3d (2) 2.63 3.08 3.71Zr 3d (3) 0.274 0.32 0.38Pb 4f (1) 16.22 18.89 18.99 22.12 22.82 26.58Pb 4f (2) 2.18 2.55 3.07Pb 4f (3) 0.48 0.56 0.68Suma 99.914 117.05 140.66

Pb 1.31Ti 0.75Zr 0.25O 4.62

Pb 1.31Ti 0.75Zr 0.25O 3.61

Pb 1.31Ti 0.75Zr 0.25O 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, 044105 (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 PHYSICSN.G. Gheorghe, G.A. Lungu, C.M. Teodorescu, I. Pintilie, L. Trupina, C. Dragoi, “Photoelectron spectroscopy studies of pulsed laser deposited Pb(Zr,Ti)O3-δ single crystal films”, sent to PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS