Ferroelectric films for optical and piezoelectric applications (NNS.4191)

Ferroelectric thin films are important materials for integrated optical and piezoelectric applications (e.g. switches, actuators, sensors). A crucial aspect for all possible future large scale production and application is the dependence of the macroscopic properties on the film composition and microstructure. Potentially MOCVD is the best technique for industrial upscaling. This proposal aims to combine the efforts at RIM (fundamental study of relation between growth and ferroelectric and optical properties) with those of MESA (options for microelectromechanical and optical devices).
At RIM films of (Pb,La)(Zr,Ti)O₃ (PLZT) and BaTiO₃ (BT) will be prepared. MOCVD for the thickness range (0.5-5 microm.) envisaged, together with the study of the relation between properties and microstructure (how can these be controlled?), are the chalenges. For piezoelectric applications deposition will be carried out on Pt-coated Si-substrates; for optical both polycrystalline and lattice-matched substrates will be used. Information about microstructure, interface roughness, polarization state, domain studies, etc. will be obtained by measuring a.o. ellipsometry and the SHG-response.
At MESA-IO the films will be characterised (complex) index of refraction n,k and the linear electro-optic coefficient, the absorption in the wavelength range 400-1550 nm. An optical demonstrator consisting of an electro-optic modulator will be designed and fabricated. At MESA-M the piezoelectric properties will be determined. Three different types of demonstrators (micro-valve, impact sensor, force sensor) will be produced.

Resultaten van het onderzoek

PbZr_xTi_1-xO₃ thin films have been successfully deposited by MOCVD at RIM on both platinized silicon substrates and SrTiO₃ crystals. The polycrystalline films on platinized substrates are up to now from 50 to 300 nm thick. The films are deposited in the appropriate stochiometry and exhibit ferroelectric properties (Figures 1, 2). Structural and morphological studies have been performed by XRD and SEM. The platinized silicon wafers have also been studied: diffusion of the Ti adhesion layer, roughness, etc.. induce an interfacial layer between the Pt substrate and the PZT film. The piezoelectric coefficient of 100 nm thick polycrystalline films, measured by cantilever deflection with a Mach Zehnder Interferometer, was found to be: d₃₁= - 65 pC/N. The PZT films on (001) SrTiO₃ crystals are 60 to 130 nm thick and allow optical measurements (Figure 3). We will carry on with the PZT growth on SrTiO₃ and optical properties.

Publicaties

• "MOCVD PbZr_xTi_1-xO₃ Thin Films on Platinized Silicon Wafers and SrTiO₃ Crystals : Growth and Optical Properties", Mona P. Moret, Marijn A.C. devillers, Andy R.A. Zauner, Edwin Aret, Paul R. Hageman, Poul K. Larsen, submitted to Integrated Ferroelectrics (ISIF 2001 proceedings)
• "Local Probing of the polarization state in thin Pb(ZrTi)O3 films during polarization reversal" E.D. Mishina, N.E. Sherstyuk, E.Ph. Pevtsov, K.A. Vorotilov, S.A. Sigov, M.P. Moret, ,S.A. Rössinger, P.K. Larsen, and Th. Rasing, Appl.Phys.Letters 78 (6), 796 - 798, (2001)
• "MOCVD Growth and Characterization of PbTiO₃ Thin Films on Pt/Ti/SiO₂/Si Substrates", M.P.Moret, S.A. Rössinger, P.R. Hageman, S.I. Misat M.A.C. Devillers, H.van der Linden, E. Haverkamp, W.H.M. Corbeek, P.K. Larsen, Integrated Ferroelectrics 31, 305-314, (2000)
• "Incorporation of Pb, Ti and Zr into MOCVD Grown PbZr_xTi_1-xO₃ thin films" S.A. Rössinger, M.P.Moret, S.I. Misat, P.R. Hageman, H van der Linden, E. Haverkamp, W.H.M. Corbeek, and PK. Larsen, Integrated Ferroelectrics 30, 71-79, (2000)
• "Interfacial Layer Observed by Ellipsometry in MOCVD Grown Pb(Zr,Ti)O₃ Thin Films" M.P.Moret, S.A. Rssinger, P.R. Hageman, M.A. devillers, H.van der Linden, E. Haverkamp, P.K. Larsen, and N. Duan Ferroelectrics 241, 149-158 (2000)

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Laatste wijziging: 03-05-2001
Reacties naar webmaster@stw.nl

Gebruikers

Er zijn vijf bedrijven bij dit project betrokken.

Projectleider

Prof.dr. P.K. Larsen
Katholieke Universiteit Nijmegen
Faculteit Natuurkunde
Research Institute for Materials
Toernooiveld
6525 ED NIJMEGEN.

Status van het project

Gestart	: 16-11-1997
Einddatum	: 01-03-2003

Trefwoorden

IC-technologie, microsysteemtechnologie, geïntegreerde optica, depositietechniek, SHG (second harmonic generation), microelectronica, ferroelectrisch, piezo-effect, krachtsensor, MOCVD, materialen, electro-optica, perovskite.

PbZr_xTi_1-xO₃ thin films on SrTiO₃ : optical properties

Figure 3: Optical properties of the PZT films on SrTiO_3. The refractive index was measured by ellipsometry at labda= 500, 600, 700, 800 nm ) and the data were interpolated by a Cauchy fit and extrapolated up to 2000 nm.