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Stockholm, S-100 44, Sweden.

ABSTRACT Highly c-axis oriented Na 0.5 K0.5 NbO 3 (NKN) films have been prepared on thermally grown thin SiO 2 template layer onto Si(001) wafer by pulsed laser deposition technique. Xray diffraction 0-20-scan data show multiple-cell structuring along the polar axis in NKN films grown onto SiO 2 with thickness up to 45 nm. On the other hand, the film deposited onto amorphous ceramic (Coming) glass is a mixture of slightly c-axis oriented NKN and pyrochlore phases, while the film onto Pt(lll)/Ti/SiO 2/Si(001) shows perfect [111] orientation. This implies small amount of SiO 2 crystallites distributed in amorphous silica matrix inherits Si(001) orientation and serves as a key factor in highly oriented growth of NKN films. Au upper electrodes have been defined on the top of NKN(270nm)/SiO2/Si structures to investigate Metal-Ferroelectric-Insulator-Silicon (MFIS) diode characteristics for Field Effect Transistor (MFIS-FET) nonvolatile memory applications. C-V measurements yield memory window of 4.14 V at 10 V of gate voltage.

INTRODUCTION Silicon, the essential material of the semiconductor industry, is one of the most desirable substrate. Recent years there have seen extensive studies on the synthesis of perovskite materials: high temperature superconductors, giant and colossal magnetoresistors, and ferroelectrics for integration with semiconductor devices. One of the main difficulties in fabrication of high quality multi-component oxide film directly onto Si substrate lies in interdiffusion of cations through the film-substrate interface, though there is a favourable pseudoepitaxial affinity between the size of the edge of Si cubic cell and the diagonal of the perovskite unit cell in (ab) plane. Therefore a lot of materials such as yttrium stabilized zirconia (YSZ), CeO 2, MgO, and SrTiO 3 have been introduced as a buffer layer between Si substrate and perovskite films. [1] However, the fabrication of a buffer layer of exceptional quality has turned out a very difficult problem. Thermally grown Si0 2 film seems to be the ideal buffer layer since it shows a remarkably small number of electronic defects [2], hence superior performances, i.e. capacitance-voltage (C-V) and current-voltage (I-V) characteristics are expected in SiO2/Si structure based devices. Nevertheless, only few studies on crystalline relation between perovskite thin film and SiOjSi substrates have been reported. In this article, we present highly c-axis oriented NKN thin films on thermally grown ultra-thin Si0 2 layer onto Si(001) wafers, and memory properties of Au/NKN/Si0 2/Si (MFIS) structure.

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Mat. Res. Soc. Symp. Proc. Vol. 623 © 2000 Materials Research Society

EXPERIMENTAL PROCEDURES Thin SiO 2 layers with various thickness from native to 45 nm have been thermally grown onto Si(001) substrates. The details of oxidation processes are described elsewhere. [3] A KrF excimer laser (Lambda physik-300, X = 248 nm, pulse width of 25 nm) has been used to ablate stoichiometric NKN target with the energy density of 4-