Hyun Woo Chung

Effect of double-sided (Pb0.72La0.28)Ti0.93O3 buffer layers on the ferroelectric properties of Pb(Zr0.52Ti0.48)O3 thin films

We deposited the Pb(Zr0.52Ti0.48)O3 (PZT) thin films with single and double-sided (Pb0.72La0.28)Ti0.93O3 (PLT) buffers by using a pulsed-laser deposition method. With the PLT buffer layers, the remanent polarization values increased, and a remanent polarization value of 33.4μC∕cm2 was obtained when 10-nm-thick double-sided PLT buffer layers were used. While the coercive field of films slightly increased only with a single-sided PLT buffer, it decreased again by adding the top PLT buffer layer. The film with double-sided PLT buffer also exhibited good fatigue endurance after 109 switching cycles even without oxide electrodes, mainly because the accumulated charges were compensated at the interface junction between the PLT buffer layer and the electrode.

Photophysical properties of N-confused hexaphyrins: effects of confusion of pyrrole rings and molecular shape on electronic structures

Doubly and triply N-confused hexaphyrins revealed quite unique photophysical properties arising from confusion of pyrrole rings in the macrocycle, and the molecular shape when compared with their parent regular hexaphyrin molecules.

Comparison of forming gas effects on the ferroelectric properties between more-oriented and less-oriented Pb(Zr0.52Ti0.48)O3 thin films

More-oriented and less-oriented Pb(Zr0.52Ti0.48)O3 (PZT) thin films were deposited by using a pulsed-laser deposition method on a Pt∕Ti∕SiO2∕Si substrate with (Pb0.72La0.28)Ti0.93O3 buffer and on a Pt∕Ti∕SiO2∕Si substrate without buffer, respectively, which were observed by x-ray diffraction patterns. These films were annealed in H2-contained ambient for 30 min at the substrate temperature of 400 °C to evaluate the forming gas annealing effects. The comparative studies on the ferroelectric properties of these two films were carried out that showed that ferroelectric properties such as remanent polarization did not change in the case of the more-oriented PZT film, whereas the remanent polarization value of the less-oriented lead zirconate titanate (PZT) film degraded from 20.8 to 7.3μC∕cm2. The leakage current became higher in both cases, but that of the more-oriented PZT film had the moderate value of the 10−6 order of A∕cm2. This is mainly because the hydrogen atoms that cause the degradation of PZT film...

Hydrogen resistive double-side (Pb0.72La0.28)Ti0.93O3 buffered Pb(Zr0.52Ti0.48)O3 thin films

The hydrogen annealing effect and the fatigue resistance of the Pb(Zr0.52Ti0.48)O3 (PZT) thin films with double-side (Pb0.72La0.28)Ti0.93O3 (PLT) buffer layers were investigated. With the PLT buffer layers, the films showed better hydrogen resistance than the PZT films because of the enhancement of the structural properties of the double-side PLT buffered PZT films. This structure also exhibited good fatigue endurance after 109 switching cycles even without oxide electrodes, mainly because the accumulated charges were compensated at the interface between the PLT buffer layers and the electrode. Moreover, the fatigue endurance was maintained even after the hydrogen annealing, so we could confirm the reliability of the structure after the fabrication process.

Piezoelectric and dielectric properties of Pb(Zr,Ti)O3–Pb(Mn,W,Sb,Nb)O3 with Ag2O addition

The effects of Ag2O addition on the dielectric and piezoelectric properties of 0.96Pb(Zr,Ti)O3–0.04Pb(Mn,W,Sb,Nb)O3 (PZT–PMWSN) ceramics and thin films deposited on a Pt∕Ti∕SiO2∕Si substrate by pulsed laser deposition have been investigated. By varying the contents of silver from 0∼3mol.%, the effect of Ag2O addition on PZT–PMWSN ceramics and thin film was systematically observed. No reaction between silver and PZT is observed in X-ray diffraction analysis. Enhanced sinterability of PZT–PMWSN ceramics with Ag2O addition increased the electromechanical quality factor (kp) and mechanical quality factor (Qm). As silver content increased, it was observed that the relative dielectric constant (ϵr) increased because of increasing effective dielectric field in the dielectric phase.