Arnaud-Gides Moussavou

Towards the integration of epitaxially grown KTN thin films in silicon technology

The use of a high quality SrTiO 3 buffer layer was investigated in order to give access to the integration in standard silicon technology of KTa 1 − x Nb x O 3 thin films, grown by pulsed laser deposition. The buffer layer was previously epitaxially grown onto Si substrates by molecular beam epitaxy, using a process implying seed and sacrificial layers of strontium. The 40 nm thick SrTiO 3 underlayer acts together as a matching layer, a seed layer and an anti-diffusion barrier, preventing the formation of the undesired competing pyrochlore phase. High crystalline quality perovskite single-phase epitaxial KTa 1 − x Nb x O 3 thin films were reproducibly obtained by the use of this process.

KTa0.5Nb0.5O3 ferroelectric thin films: processing, characterization and application to microwave agile devices

This paper is aimed at demonstrating the high capabilities of KTa0.5Nb0.5O3 thin films for microwave agility applications. Tunable capacitors, resonators and phase shifters were realized with KTN materials. Their high frequency measurements showed, in particular, the very high tuning factors of these films under quite low electric field.

Study of planar transmission lines printed on a ferroelectric thin Film: Optimum tunability and figure of merit

In this paper, we report on simulation results at 10 GHz of different configurations of planar transmission lines (TL) printed on a ferroelectric thin film deposited on sapphire and lanthanum aluminate substrates. The ferroelectric material is KTa0.5Nb0.5O3 (KTN) and its film permittivity is supposed to vary from 700 to 500. First, we present the analyses results of KTN thin films coated considered substrates. Then the main properties of microstrip (MS), coplanar waveguide (CPW) and coplanar strips (CS) are computed as a function of the physical and electrical parameters. Their tunability and figure of merit are defined and compared. CPW and CS lines present a tunability (¿eff/effmax) of about 16 % for a gap value g = 30 ¿m. The MS lines show a much less tunability of 2%. The figure of merit of CPW and CS configurations are of 6.3 and 12.2 %/dB for a gap value of 30 ¿m, respectively. By increasing the gap, these figures of merit can be improved up to the limiting values of 8.7 and 15.4 %/dB, respectively.