High-frequency characterisation of ferroelectric thin film capacitors and their integration for frequency tunable antennas

International audienc

Tungsten based electrodes for stacked capacitor ferroelectric memories

Fabrication of high-density ferroelectric memories requires the growth of the ferroelectric material on the drain contact metal. In standard 0.5 mum technology, tungsten plugs are applied to connect the drain contacts to the first metallization level. In this work, we investigated electrode systems to be applied between sputter deposited, ferroelectric PbZr0.35Ti0.65O3 (PZT) and tungsten. Besides the obvious barrier function of such an electrode system, the texture of the PZT is of interest as well. The roughness of chemical vapor deposition (CVD) of W layer before and after etch-back by dry etching resulted in an increased leakage current of the ferroelectric capacitor. The problem could be solved by chemical mechanical polishing (CMP) of the tungsten film

Epitaxial growth of iridium thin films: a comparison between plasma vs. laser processing

International audienc

Influence of microstructure and Ba/Sr ratio on high tunability of (Ba,Sr)TiO3 thin film based-capacitors

National audienc

Electrode interface controlled electrical properties in epitaxial Pb(Zr0.52Ti0.48)O-3 films grown on Si substrates with SrTiO3 buffer layer

International audienceElectrical properties of ferroelectric capacitors based on PbZr0.52Ti0.48O3 thin films grown by pulsed laser deposition on silicon substrate with SrTiO3 buffer layer grown by molecular beam epitaxy were studied. A SrRuO3 layer was deposited as bottom electrode also by pulse laser deposition and Pt, Ir, Ru, SrRuO3 were used as top contacts. Electrical characterization comprised hysteresis and capacitance-voltage measurements in the temperature range from 150 K to 400 K. It was found that the macroscopic electrical properties are affected by the electrode interface, by the choice of the top electrode. However, even for metals with very different work functions (e.g. Pt and SrRuO3) the properties of the top and bottom electrode interfaces remain fairly symmetric suggesting a strong influence from the bound polarization charges located near the interface. (C) 2015 Elsevier B.V. All rights reserved

Laser processing of para-/ferro-electric ceramics as thin films for highly-tunable microcapacitors

International audienc

Comparison between the ferroelectric/electric properties of the PbZr0.52Ti0.48O3 films grown on Si (100) and on STO (100) substrates

International audienceFerroelectric/electric properties of PbZr0.52Ti0.48O3 (PZT) thin films grown by pulsed laser deposition (PLD) on two different substrates, Si (001) and SrTiO3 (STO) (001), were comparatively analyzed. The structural characterization has revealed the epitaxial relationship between the grown layers and the two types of substrates, with larger density of structural defects for the films deposited on Si (001) with buffer STO layer. The ferroelectric/electric properties are also different, with lower remnant polarization (about half of the value obtained on STO substrate), higher dielectric constant (about two times larger), and lower leakage current (about two orders of magnitude lower) for the PZT films deposited on Si (001) compared to those deposited on (001) STO substrates. Nevertheless, the results show that the use of a STO buffer layer on Si can be a solution to obtain good quality PZT capacitor structures without using expensive single-crystal oxide substrates. In this way, applications based on PZT capacitors (e.g. non-volatile memories, pyroelectric detectors, light switches, etc.) would be more easily integrated directly on Si wafers

Pulsed laser deposition of thin film capacitors with applications in highly tunable digital and analogic microwave devices

International audienc

Para-/ferro-electric films grown by pulsed laser deposition for various configurations of high frequency tunable microcapacitors

International audienc

CO adsorption, reduction and oxidation on Pb(Zr,Ti)O3(001) surfaces associated with negatively charged gold nanoparticles

Gold is deposited on atomically clean, inwards polarized, ferroelectric lead zirco-titanate deposited by pulsed laser deposition on strontium titanate (001) single crystal, then carbon monoxide adsorption and desorption experiments are investigated by in situ fast photoelectron spectroscopy using synchrotron radiation. Atomic force microscopy and high resolution photoelectron spectroscopy are consistent with the formation of 50\u2013100 nm nanoparticles, and their Au 4f core levels point to a negative charge state of gold. As compared with a similar experiment performed on ferroelectric lead zirco-titanate with similar polarization state and without gold, the saturation coverage after exposure to carbon monoxide increases by about 68 %, and also most of the additional carbon is found in oxidized state. Desorption experiments with in situ follow-up by photoelectron spectroscopy are performed as function of temperature, and the neutral carbon intensity decreases when the ferroelectric polarization decreases, while the components corresponding to oxidized carbon remain unchanged. It looks that neutral carbon adsorption is strictly related to the polarization of the ferroelectric film, while carbon still found in molecular form is related to its carbonyl bonding on metal nanoparticles, independent of the polarization state of the substrate. Desorbed carbon at higher temperature uptakes oxygen from the substrate