Toward Design Rules for Multilayer Ferroelectric Energy Storage Capacitors - A Study Based on Lead-Free and Relaxor-Ferroelectric/Paraelectric Multilayer Devices.

Future pulsed-power electronic systems based on dielectric capacitors require the use of environment-friendly materials with high energy-storage performance that can operate efficiently and reliably in harsh environments. Here, a study of multilayer structures, combining paraelectric-like BaSrTiO (BST) with relaxor-ferroelectric BaZrTiO (BZT) layers on SrTiO-buffered Si substrates, with the goal to optimize the high energy-storage performance is presented. The energy-storage properties of various stackings are investigated and an extremely large maximum recoverable energy storage density of ≈165.

Interfacial dielectric layer as an origin of polarization fatigue in ferroelectric capacitors.

Origins of polarization fatigue in ferroelectric capacitors under electric field cycling still remain unclear. Here, we experimentally identify origins of polarization fatigue in ferroelectric PbZrTiO (PZT) thin-film capacitors by investigating their fatigue behaviours and interface structures. The PZT layers are epitaxially grown on SrRuO-buffered SrTiO substrates by a pulsed laser deposition (PLD), and the capacitor top-electrodes are various, including SrRuO (SRO) made by in-situ PLD, Pt by in-situ PLD (Pt-inPLD) and ex-situ sputtering (Pt-sputtered).

Large piezoelectric strain with ultra-low strain hysteresis in highly c-axis oriented Pb(ZrTi)O films with columnar growth on amorphous glass substrates.

Thin films of PbZr.Ti.O (PZT) with largely detached columnar grains, deposited by pulsed laser deposition (PLD) on amorphous glass substrates covered with CaNbO nanosheets as growth template and using LaNiO electrode layers, are shown to exhibit very high unipolar piezoelectric strain and ultra-low strain hysteresis.

Controlling Piezoelectric Responses in Pb(ZrTi)O Films through Deposition Conditions and Nanosheet Buffer Layers on Glass.

Nanosheet CaNbO (CNOns) layers were deposited on ultralow expansion glass substrates by the Langmuir-Blodgett method to obtain preferential (001)-oriented growth of Pb(ZrTi)O (PZT) thin films using pulsed laser deposition (PLD) to enhance the ferroelectric and piezoelectric properties of the films. The PLD deposition temperature and repetition frequency used for the deposition of the PZT films were found to play a key role in the precise control of the microstructure and therefore of the ferroelectric and piezoelectric properties. A film deposited at a high repetition frequency has a columnar grain structure, which helps to increase the longitudinal piezoelectric coefficient (d).

Strongly Enhanced Piezoelectric Response in Lead Zirconate Titanate Films with Vertically Aligned Columnar Grains.

Pb(ZrTi)O (PZT) films with (001) orientation were deposited on Pt(111)/Ti/SiO/Si(100) substrates using pulsed laser deposition. Variation of the laser pulse rate during the deposition of the PZT films was found to play a key role in the control of the microstructure and to change strongly the piezoelectric response of the thin film. The film deposited at low pulse rate has a denser columnar microstructure, which improves the transverse piezoelectric coefficient (d) and ferroelectric remanent polarization (P), whereas the less densely packed columnar grains in the film deposited at high pulse rates give rise to a significantly higher longitudinal piezoelectric coefficient (d) value.

Properties of epitaxial, (001)- and (110)-oriented (PbMgNbO)-(PbTiO) films on silicon described by polarization rotation.

Epitaxial (PbMgNbO)-(PbTiO) (PMN-PT) films with different out-of-plane orientations were prepared using a CeO/yttria stabilized ZrO bilayer buffer and symmetric SrRuO electrodes on silicon substrates by pulsed laser deposition. The orientation of the SrRuO bottom electrode, either (110) or (001), was controlled by the deposition conditions and the subsequent PMN-PT layer followed the orientation of the bottom electrode. The ferroelectric, dielectric and piezoelectric properties of the (SrRuO/PMN-PT/SrRuO) ferroelectric capacitors exhibit orientation dependence.

Highly Oriented Growth of Piezoelectric Thin Films on Silicon Using Two-Dimensional Nanosheets as Growth Template Layer.

CaNbO (CNOns) and TiO (TiOns) metal oxide nanosheets (ns) are used as a buffer layer for epitaxial growth of piezoelectric capacitor stacks on Si and Pt/Ti/SiO/Si (Pt/Si) substrates. Highly (001)- and (110)-oriented Pb(ZrTi)O (PZT) films are achieved by utilizing CNOns and TiOns, respectively. The piezoelectric capacitors are characterized by polarization and piezoelectric hysteresis loops and by fatigue measurements.

Intrinsic stability of ferroelectric and piezoelectric properties of epitaxial PbZrTiO thin films on silicon in relation to grain tilt.

Piezoelectric thin films of PbZrTiO were grown on Si substrates in four different ways, resulting in different crystalline structures, as determined by x-ray analysis. The crystalline structures were different in the spread in tilt angle and the in-plane alignment of the crystal planes between different grains. It is found that the deviations of the ferroelectric polarization loop from that of the ideal rectangular loop (reduction of the remanent polarization with respect to the saturation polarization, dielectric constant of the film, slanting of the loop, coercive field value) all scale with the average tilt angle.

High-temperature magnetic insulating phase in ultrathin La0.67Sr0.33MnO3 films.

We present a study of the thickness dependence of magnetism and electrical conductivity in ultrathin La0.67Sr0.33MnO3 films grown on SrTiO3 (110) substrates.

Josephson junctions and DC SQUIDS based on Nb/Al technology.

A process for fabricating high-quality Josephson junctions and DC SQUIDs on basis of Nb/Al technology has been developed. DC magnetron sputtering is used for the deposition of the metal layers and the barrier is formed by thermal oxidation of the Al-layer. The junction area of 5 microns x 5 microns is obtained using anodisation.