N. Y. Chan

Enhanced ferroelectric and piezoelectric properties in doped lead-free (Bi0.5Na0.5)0.94Ba0.06TiO3 thin films

Doping effects with respect to the electrical properties of morphotropic phase boundary (Bi0.5Na0.5)0.94Ba0.06TiO3 thin films epitaxially grown on CaRuO3 electroded (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) substrates were investigated. Substantial enhancement of ferroelectricity and piezoelectricity has been achieved in La+Ce codoped films with a remanent polarization Pr of 29.5 μC/cm2 and a remanent piezoelectric coefficient d33,f of 31 pm/V, whereas Mn doping seems more favorite to reduce the leakage current by two order of magnitude. Both doped films exhibited diodelike I-V characteristics, which are correlated with resistance switching effect.

Polar Liquid Molecule Induced Transport Property Modulation at LaAlO3/SrTiO3 Heterointerface

IO N New and unexpected physical properties that are absent in their individual bulk constituents have triggered intensive research interest in polar oxide heterointerfaces. [ 1 ] One sparkling example is the discovery of two-dimensional electron gas (2DEG) generated at the interface between two band insulators, LaAlO 3 (LAO) and SrTiO 3 (STO), [ 2 , 3 ] which has revealed intriguing electronic properties [ 4–8 ] and a rich superconducting phase diagram [ 9 , 10 ] at low temperature. These signifi cant results promise potential applications of this oxide interface in new generation of electronics. [ 11 , 12 ]

Multiferroism in orientational engineered (La, Mn) co-substituted BiFeO3 thin films

Orientational engineered (La, Mn) co-substituted BiFeO3 (LMBFO) thin films were epitaxially grown on CaRuO3 electroded (LaAlO3)0.3(Sr2AlTaO6)0.35 (LSAT) single crystal substrates by pulsed laser deposition. The experimental results demonstrate that the crystallographic orientation is the critical dominant of the structural and multiferroic properties of LMBFO thin films. Giant remanent polarization of 65, 92, and 106 μC/cm2 for [001], [110], [111]-oriented films, respectively, were demonstrated at room temperature. Saturated magnetization is also significantly dependent on film orientation with the highest value of 12.8 emu/cm3 along [001] direction. The variation in leakage current density and ferroelectric coercivity were ascribed to the substantially difference of ferroelectric domain structures in variously oriented LMBFO thin films.

The structural and in-plane dielectric/ferroelectric properties of the epitaxial (Ba, Sr)(Zr, Ti)O3 thin films

Epitaxial (Ba1-xSrx)(Zr0.1Ti0.9)O3 (BSZT, x = 0 – 0.45) thin films were deposited on (LaAlO3)0.3(Sr2AlTaO6)0.35 (LSAT) substrates by pulsed laser deposition. The experimental results demonstrate that the structural, dielectric, and ferroelectric properties of the BSZT thin films were greatly dependent on the strontium content. The BSZT thin films transformed from tetragonal to cubic phase when x ≥ 0.35 at room temperature. The Curie temperature and room-temperature remnant polarization decrease with increasing strontium concentration. The optimal dielectric properties were found in (Ba0.55Sr0.45)(Zr0.1Ti0.9)O3 thin films which is in paraelectric state, having tunability of 47% and loss tangent of 0.0338 under an electric field of 20 MV/m at 1 MHz. This suggests that BSZT thin film is a promising candidate for tunable microwave device applications.

Barium Strontium Zirconate Titanate (Ba,Sr)(Zr,Ti)O3 Thin Films for Tunable Microwave Applications

(Ba0.55Sr0.45)(Zr0.1Ti0.9)O3 (BSZT) thin films were deposited by pulsed laser deposition on LSAT(001) substrates. X-ray diffraction characterization reveals a good quality of crystallization and epitaxial nature of the films. The in-plane dielectric properties of the films were characterized over a wide frequency range from 50 MHz to 20 GHz by using ring resonator-structured samples. Based on the S-parameter measurements and electromagnetic simulation it was found that microwave dielectric constant of the BSZT thin film is ∼350. Large dielectric tunability was also observed in this material.

Orientational dependence of multiferroic behaviors of La and Mn modified BiFeO 3 thin films

Orientation engineered (La, Mn) co-substituted BiFeO<inf>3</inf> [BFOLM] thin films were deposited on CaRuO<inf>3</inf> buffered (LaAlO<inf>3</inf>)<inf>0.3</inf>(Sr<inf>2</inf>AlTaO<inf>6</inf>)<inf>0.35</inf> [LSAT] [001], [110] and [111] single crystal substrates, respectively, by pulsed laser deposition. Highly epitaxial growth and sharp interfaces of the BFOLM /CaRuO<inf>3</inf>/LSAT heterostructures were revealed by x-ray diffraction and high resolution transmission electron microscopy. Their ferroelectric and ferromagnetic properties are strongly dependent on the crystallographic orientation. At 1 kHz and room temperature, the remanent polarization P<inf>r</inf> were found to be 65, 92, and 106 µC/cm² for the [001], [110] and [111]-oriented films, respectively. While the largest saturated magnetic moment M<inf>s</inf> was along [001] direction with the value of ∼ 12.8 emu/cm³. Anisotropic dielectric behaviors were also observed in differently oriented BFOLM thin films.