Ralph Klarmann

PLD of Pb(Zr,Ti)O3 films: Phase formation on various substrates

Abstract Pulsed laser deposition (PLD) was used to deposit Pb(Zr 52 Ti 48 )O 3 (PZT-5A) thin films on various substrates (SrTiO 3 , MgO, polycrystalline Yttria-stabilized ZrO 2 (YSZ) and Al 2 O 3 ). Furthermore, epitaxial YBa 2 Cu 3 O 7− x on SrTiO 3 /Al 2 O 3 , which is serving as bottom electrode, was covered with PZT by PLD. The phase formation of two phases of PZT, the stable ABO 3 with perovskite structure and the metastable A 2 B 2 O 6 O phase with pyrochlore structure, was investigated by XRD in dependence of substrate material, deposition temperature and film thickness. The ferroelectric P(E)-hysteresis of the films was measured and discussed with respect to the above mentioned points. A favoring of the perovskite phase formation was found on SrTiO 3 , a mixture of perovskite and pyrochlore on MgO, whereas YSZ substrates lead to the growth of 100% pyrochlore films under comparable deposition conditions. On polycrystalline Al 2 O 3 substrates an additional YBCO layer allows the deposition of almost pure perovskite PZT.

Patterning of YBCO thin films by ion implantation and magneto-optical investigations

Abstract YBa 2 Cu 3 O 7− δ thin films deposited by pulsed laser deposition were patterned by ion implantation. The patterning technique is based on the local disordering of the crystal structure due to elastic collisions of the implanted O + -ions and thus on a strong breakdown of superconductivity in the irradiated areas. With this patterning method circular and meandering structures with a size of 1 mm were prepared for investigations regarding high current applications. O + -ions with an energy of 180 keV were used to avoid a contamination of the film. The achieved structures were investigated concerning a dependence on the dose by means of RBS, XRD, AFM and magneto-optical characterization. Using a fluence of 5×10 14 O + /cm 2 a fully planar and stable structure can be obtained. The patterning depth can be adjusted by varying the implantation energy. So this technique was also used successfully on YBCO thin films covered already with a 200 nm Au top layer.

Pulsed laser deposition of YBCO thin films on 7×20-cm2 substrates

Abstract A specially designed and patented setup has been built up for Pulsed Laser Deposition (PLD) of homogeneous YBa 2 Cu 3 O 7− x (YBCO)-films on substrates as large as 7×20 cm 2 . YBCO films have been deposited on small substrates (SrTiO 3 , LaAlO 3 and buffered polycrystalline YSZ). Their structural and superconducting properties have been measured. The mean values of the transition temperatures and the critical current densities at T =77 K and zero magnetic field on single crystal substrates are 90 K and 4.3 MA/cm 2 , respectively. The YBCO films on buffered polycrystalline YSZ substrates reach critical current densities up to 1.1 MA/cm 2 at T =77 K and B =0 T.

Correlation between structural, ferroelectric and dielectric properties of laser ablated (Pb0.92La0.08)(Zr0.65Ti0.35)O3 - thin-films on high-grade steel hastelloy

Abstract High-grade steel Hastelloy was covered with (Pb0.92La0.08)(Zr0.65Ti0.35)O3 (PLZT) by Pulsed Laser Deposition (PLD). The direct deposition of the ferroelectric thin film on the substrate material - without additional buffer layers or bottom electrodes beneath the PZT - leads to a simple bicomponental system. The deposited films were characterized with respect to their structural properties (XRD, AFM) and showed excellent ferroelectric behavior [P(E) hysteresis]. Furthermore the fatigue, retention and ageing behavior of PLZT on Hastelloy was investigated and showed strong correlations to the structural measurements. Dielectric spectroscopy was used to investigate the frequency and temperature dependence of the permittivity ε. These measurements were discussed with respect to the above mentioned points.

Influence of ion implantation on the ferroelectric properties of Pb(Zr,Ti)O/sub 3/ films

Pulsed laser deposition (PLD) was used to deposit Pb(Zr,Ti)O/sub 3/ (PZT) and (Pb,La)(Zr,Ti)O/sub 3/ (PLZT) thin films on YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO)//MgO and on technical substrates (high-grade steel Hastelloy). As a typical characterization of ferroelectric materials the P(E) hysteresis loop reflects the mobility of ferroelectric domain walls. We investigate the influence of ion implantation on the ferroelectric behaviour of thin PZT-films produced by PLD. The species of implanted ions (O/sup +/,Ca/sup +/) and the doses (10/sup 14/-10/sup 16/ cm/sup -2/, 180 keV) were varied to study the influence of the introduced atoms and defects on the ferroelectric properties. The films were investigated by XRD, RBS/Channeling and a RT-66A ferroelectric tester. The influence of thermal treatment of the implanted PZT-films on their ferroelectric properties will be discussed above the background of the induced structural defects and the implanted ions itself.

Ferroelectric properties of Pb(Zr,Ti)O/sub 3/-films on technical substrates

Pulsed laser deposition (PLD) was used to deposit Pb(Zr,Ti)O/sub 3/ (PZT) based oxide ceramics on various technical substrates (polycrystalline Al/sub 2/O/sub 3/, high-grade steel Hastelloy). Most work in the ferroelectric field up to now has been directed towards single crystalline substrates. For the purpose of a ferroelectric print-process application our research presently concentrates on technical and low-cost substrates.