Xuedong Li

Influence of electrode configuration on dielectric properties of ferroelectric films with interdigital and parallel plate electrodes

The interdigital electrodes (IDEs) and parallel plate electrodes (PPEs) were prepared by photolithographic techniques and dc sputtering on rf magnetron sputtered lanthanum-modified lead titanate (PLT) films, respectively. The PLT films with IDEs and PPEs exhibit almost the same permittivity at 1kHz, while the dielectric constant and loss of PLT films with IDE decrease faster than those of the films with PPE as increasing the frequency. The permittivity of the films with IDE can be calculated using a previously developed analytical model. The reasons for the impact of the IDE and PPE on dielectric properties of the films were discussed.

Preparation and charaterization of high (100) oriented PSTT5 thin flims by RF sputtering technology

0.95Pb(Sc<inf>0.5</inf>Ta<inf>0.5</inf>)O<inf>3</inf>-0.05PbTiO<inf>3</inf>(PSTT5) thin films were prepared on LaNiO<inf>3</inf>(LNO)/SiO<inf>2</inf>/Si substrate by RF sputtering technology. After sputtering, the PSTT5 thin films were annealed by normal one-step rapid thermal annealing (OSRTA) or a renovation of two-step rapid thermal annealing (TSRTA). The PSTT5 films annealed by TSA show high (100) orientation, high phase purity, sufficient crystallization and enhanced ferroelectric properties. The TSRTA mechanism was also discussed.

Effect of two-steps RTA on the properties of PSTT5 thin films

0.95Pb(Sc<inf>0.5</inf>Ta<inf>0.5</inf>)O<inf>3</inf>-0.05PbTiO<inf>3</inf> (PSTT5) ferroelectric thin films have been prepared by RF magnetron sputtering on LSCO/Pt/Ti/ SiO<inf>2</inf>/Si(100) substrates. A new two-steps rapid thermal annealing (TSRTA) was developed. TSRTA and conventional rapid thermal annealing (CRTA) were both used to anneal PSTT5 thin films. The XRD patterns shows that the PSTT5 thin films annealed by TSRTA would form pure perovskite structure and show highly (220) oriented. The ferroelectric measurements indicate that the PSTT5 thin films annealed by TSRTA possess better ferroelectric property. The 2P<inf>r</inf> of the PSTT5 thin films annealed by TSRTA can be 25.4µC/cm².

Enhanced dielectric and ferroelectric properties of Pb(Zr0.8Ti0.2)O3∕Pb(Zr0.2Ti0.8)O3 multilayer films

A series of Pb(Zr1−xTix)O3 multilayer films consisted of Pb(Zr0.8Ti0.2)O3 and Pb(Zr0.2Ti0.8)O3 were deposited on Pt∕Ti∕SiO2∕Si substrates by using radio frequency magnetron sputtering. All the films comprise six periodicities of Pb(Zr0.8Ti0.2)O3∕Pb(Zr0.2Ti0.8)O3 with periodicity thickness of 133nm, but the layer thicknesses of rhombohedral phase and tetragonal phase in one periodicity are varied. The films with two layer thickness ratio of 1:3 possess enhanced dielectric and ferroelectric properties: dielectric constant er=328 at 10kHz, dielectric loss tgδ=0.0098, and sharply enhanced remanent polarization Pr=32.6μC∕cm2. The layer structure and interlayer stress of Pb(Zr1−xTix)O3 multilayer films play important roles in the electric enhancement.A series of Pb(Zr{sub 1-x}Ti{sub x})O{sub 3} multilayer films consisted of Pb(Zr{sub 0.8}Ti{sub 0.2})O{sub 3} and Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} were deposited on Pt/Ti/SiO{sub 2}/Si substrates by using radio frequency magnetron sputtering. All the films comprise six periodicities of Pb(Zr{sub 0.8}Ti{sub 0.2})O{sub 3}/Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} with periodicity thickness of 133 nm, but the layer thicknesses of rhombohedral phase and tetragonal phase in one periodicity are varied. The films with two layer thickness ratio of 1:3 possess enhanced dielectric and ferroelectric properties: dielectric constant {epsilon}{sub r}=328 at 10 kHz, dielectric loss tg{delta}=0.0098, and sharply enhanced remanent polarization P{sub r}=32.6 {mu}C/cm{sup 2}. The layer structure and interlayer stress of Pb(Zr{sub 1-x}Ti{sub x})O{sub 3} multilayer films play important roles in the electric enhancement.

Dielectric and Ferroelectric Behaviors of (100)-Oriented 0.9Pb(Sc0.5Ta0.5)O3-0.1PbTiO3 Thin Films

0.9Pb(Sc0.5Ta0.5)O3-0.1PbTiO3 (PSTT10) thin films were deposited on Si(1 0 0) substrate with a LaNiO3 buffer layer by RF magnetron sputtering technique and post annealed by a two-steps rapid thermal annealing method. Dielectric, ferroelectric behaviors and surface morphology of the films were analyzed. The films show good ferroelectric and dielectric properties which is similar to the PSTT5 thin films. The leakage current behavior of the films is according with Ohm law in a low electric field region, while it satisfies a space-charge limited conduction in a medium electric field region. With the increasing of frequency, the dielectric constant decrease and the dielectric loss increase, which shows a typical relaxor behavior. The dielectric constant of the films in low frequency band can be explained as Rayleigh law. The films exhibits crack free and uniform surface, with roughness of about 17 nm.

Effect of different annealing methods on the properties of PSTT thin films

0.95Pb(Sc<inf>0.5</inf>Ta<inf>0.5</inf>)O<inf>3</inf>-0.05PbTiO<inf>3</inf>(PSTT5) thin films were prepared on LaNiO<inf>3</inf>/SiO<inf>2</inf>/Si substrate by RF sputtering, and the films were annealed by one-step rapid thermal annealing (OSRTA) and two-steps rapid thermal annealing (TSRTA), respectively. Results show that an appropriate repeated heat treatment could improve ferroelectric and dielectric properties of PSTT5 film, P<inf>r</inf> and E<inf>c</inf> of PSTT5 thin films annealed by optimal conditions are 11.88µC/cm² and 53.71 kV/cm, respectively.

The Effect of Substrate Clamping on Laminated Magnetoelectric Composite

Abstract laminated composites on silicon or magnesium oxide substrates. The magnetoelectric voltage coefficient is calculated as function of interface coupling factor k, volume ratio of piezoelectrics to piezomagnetic, and volume ratio of substrates to composite. It was found that the magnetoelectric voltage coefficient decreases as the interface coupling factor k weakens, while the volume ratio of piezoelectrics to piezomagnetic vmax shifts to lead-rich compositions. The magnetoelectric voltage coefficient of laminated composites decreases sharply with increasing substrates thickness ratio, which shows strong substrate clamping effect to the magnetoelectric composite.