Wangzhou Shi

Doping concentration dependence of room-temperature ferromagnetism for Ni-doped ZnO thin films prepared by pulsed-laser deposition

High-quality Ni-doped ZnO thin films of single phase with preferred c-axis growth orientation were formed on Si (100) substrates by pulsed-laser deposition at room temperature. The films exhibited room-temperature ferromagnetic behaviors with saturation magnetic moment per Ni atom of 0.37μB,0.26μB,0.25μB and 0.21μB for the Ni concentration of 1, 3, 5, and 7 at. %, respectively. The decrease of ferromagnetism with doping concentration demonstrates that ferromagnetism observed at room temperature is an intrinsic property of Ni–ZnO thin films, not from any secondary phase.

Properties of highly (100) oriented Pb(Mg1∕3,Nb2∕3)O3–PbTiO3 films on LaNiO3 bottom electrodes

The 70%Pb(Mg1∕3,Nb2∕3)O3–30%PbTiO3 (PMNT) films have been fabricated on LaNiO3 (LNO) coated silicon substrate. The conductive LNO films act as a seed layer for the growth of PMNT films, which depresses the formation of pyrochlore phase and induces the high (100) preferred orientation of perovskite PMNT films. Compared with the PMNT films grown on platinum bottom electrode, the ferroelectric properties of PMNT films grown on LNO are enhanced. The frequency dependence of complex permittivity from PMNT films on LNO is the conjunct result of polarization relaxation and movement of oxygen vacancy, which can be fitted by the function containing Debye and universal dielectric response models, respectively.

Microstructure and electrical properties of Y2O3-doped ZnO-based varistor ceramics prepared by high-energy ball milling

Abstract Y2O3-doped ZnO-based varistor ceramics were prepared using high-energy ball milling (HEBM) and low-temperature sintering technique, with voltage-gradient of 1934–2197 V/rhm, non-linear coefficients of 20.8–21.8, leakage currents of 0.59–1.04 μA, and densities of 5.46–5.57 g/cm3. With increasing Y2O3 content, the voltage-gradient increases because of the decrease of ZnO grain size; the non-linear coefficient and the leakage current improve but the density decreases because of more porosity; the donor concentration and density of interface states decrease, whereas the barrier height and width increase because of the acceptor effect of Y2O3 in varistor ceramics.

INFLUENCE OF SUBSTRATE TEMPERATURE ON TRANSFORMATION OF PREFERRED ORIENTATIONS IN AlN FILMS

Polycrystalline aluminium nitride (AlN) films were deposited on silicon substrates by pulsed laser deposition (PLD) at a substrate temperature in the range room temperature (RT)-800°C. Films grown on Si(111) substrates feature (002) and (110) preferred orientations at substrate temperatures below 400°C and above 600°C, respectively. Films morphology is good enough for surface acoustic wave (SAW) devices. The mechanism for formation and transformation of different preferred orientations in AlN films is discussed.