Jinbin Wang

Raman scattering and high temperature ferromagnetism of Mn-doped ZnO nanoparticles

Raman scattering has been used to study the influence of manganese, an effective dopant to obtain ZnO diluted magnetic semiconductors, on the lattice dynamics of ZnO. It is found that Mn doping increases the lattice defects and induces two Raman vibration modes of 275 and 526cm−1. On the other hand, high temperature (TC higher than 350K) ferromagnetism is observed in Zn1−xMnxO (x⩽0.02) nanoparticles. It is found that the ferromagnetism of Zn1−xMnxO nanoparticles is strongly related to defects in ZnO.

Cubic and hexagonal structures of diamond nanocrystals formed upon pulsed laser induced liquid–solid interfacial reaction

Abstract Diamond nanocrystals with cubic and hexagonal structures have been prepared by pulsed laser induced liquid–solid (acetone1–graphite) interfacial reaction (PLIIR) at normal temperature and pressure. The structure and morphology of the resulted diamond nanocrystals were characterized by transmission electron microscopy (TEM). The Raman spectroscopy analysis of the obtained diamond nanocrystals showed that three diamond Raman lines, i.e., 1307, 1100, and 623 cm −1 were observed. Interestingly, the Raman line at 1100 cm −1 was identified to be original from nano-diamond. In addition, a new Raman line at 926 cm −1 due to diamond was observed in the Raman spectra (RS).

Multiferroic nanoparticulate Bi3.15Nd0.85Ti3O12-CoFe2O4 composite thin films prepared by a chemical solution deposition technique

Multiferroic xBi3.15Nd0.85Ti3O12–(1−x)CoFe2O4 composite thin films with x=0.5, 0.6, and 0.7 were fabricated on Pt∕Ti∕SiO2∕Si(100) substrates by a chemical solution deposition technique. X-ray diffraction shows that there are no other phases but bismuth-layered perovskite Bi3.15Nd0.85Ti3O12 and spinel CoFe2O4 phases in the films. Scanning electron microscopy reveals that CoFe2O4 aggregates locally into nanoparticles and embeds in the Bi3.15Nd0.85Ti3O12 matrix. The composite films exhibit both good ferroelectric and magnetic properties at room temperature, as well as distinct magnetoelectric coupling behaviors, which are comparable with those of multiferroic composite films with conventional Pb-based ferroelectric as a ferroelectric component.

Cubic-BN nanocrystals synthesis by pulsed laser induced liquid-solid interfacial reaction

Abstract Cubic boron nitride (c-BN) nanocrystals have been synthesized by pulsed laser induced liquid–solid interfacial reaction. It is shown that the diameters of the prepared quasi-spherical c-BN nanocrystals vary from 30 to 80 nm via transmission electron microscopy (TEM). The 2 θ values of the X-ray diffraction (XRD) peaks of the resultant c-BN nanocrystals are 43.16°, 74.16°, 90.08° and 136.1°, respectively, corresponding to the (1xa01xa01), (2xa02xa00), (3xa01xa01) and (3xa03xa01) crystalline planes of a c-BN phase. Fourier transform infrared (FTIR) spectroscopy has also been used to characterize the structure of boron nitride. The formation of c-BN nanocrystals upon pulsed laser ablation at the liquid–solid interface is discussed in detail.

Structure evolution and ferroelectric and dielectric properties of Bi3.5Nd0.5Ti3O12 thin films under a moderate temperature annealing

Bi3.5Nd0.5Ti3O12 (BNT) ferroelectric thin films were fabricated on Pt∕Ti∕SiO2∕Si(100) substrates by chemical solution deposition. Structure evolution and ferroelectric and dielectric properties of the as-prepared thin films under a moderate temperature (600–750°C) annealing were studied in detail. The experimental results showed that the BNT thin films annealed at 700°C exhibit preferred (00l) orientation, and the remnant polarization (2Pr) and dielectric constant (er) are higher (the values of 2Pr and er at 100kHz are 54μC∕cm2 and 448, respectively) than those of the deposited films annealed at other temperatures. Additionally, the mechanism concerning the dependence of electrical properties of the BNT ferroelectric thin films on the annealing temperature was discussed.

Room-temperature growth of cubic nitride boron film by RF plasma enhanced pulsed laser deposition

Abstract Cubic nitride boron (c-BN) films have been prepared on polished single crystal Si(1xa01xa01) surface at room temperature (25 °C) by radio frequency plasma enhanced pulsed laser deposition (RF-PEPLD), assisted with substrate negative bias. Components, structure and surface morphology of the deposited films were identified by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The growth mechanism of c-BN phase upon RF-PEPLD is discussed in detail, and the experimental evidence indicates that two deposition parameters, i.e., RF plasma power and substrate negative bias, played the key roles in the growth of the resulted c-BN films at room temperature.

Sizable electrocaloric effect in a wide temperature range tuned by tensile misfit strain in BaTiO3 thin films

The effects of misfit strain on the electrocaloric (EC) properties of BaTiO3 thin films arestudied by using the Landau-Devonshire thermodynamic theory. The “misfit-strain temperature” phase diagrams for different electric fields are constructed. It was found that the EC effect of a BaTiO3 thin film is strongly dependent on misfit strain. More interestingly, we found that BaTiO3 thin films with tensile misfit strain exhibit a sizable EC effect in a wider temperature range in comparison with those with compressive misfit strain.

Shape-controlled hydrothermal synthesis of ferroelectric Bi4Ti3O12 nanostructures

Single-crystalline Bi4Ti3O12 (BIT) nanostructures with various morphologies including nanoplates, lamellae, nanobelts and nanorods have been controllably synthesized by a facile hydrothermal process. The structure and morphology characterizations of BIT were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). The type of mineralizer and concentration play an important role on the structure and morphology of BIT products. A possible growth mechanism has been proposed by time-dependent experiments. In addition, UV-Vis absorption spectra have shown that the as-synthesized BIT samples have a slightly red-shift behavior. The piezoelectricity of BIT nanoplates and lamellae are confirmed by piezoresponse force microscopy. Local piezoresponse force measurements display a typical butterfly curve, indicating good ferroelectric property of the BIT nanoplates and lamellae.

Organic–Inorganic Copper(II)-Based Material: A Low-Toxic, Highly Stable Light Absorber for Photovoltaic Application

Lead halide perovskite solar cells have recently emerged as a very promising photovoltaic technology due to their excellent power conversion efficiencies; however, the toxicity of lead and the poor stability of perovskite materials remain two main challenges that need to be addressed. Here, for the first time, we report a lead-free, highly stable C6H4NH2CuBr2I compound. The C6H4NH2CuBr2I films exhibit extraordinary hydrophobic behavior with a contact angle of ∼90°, and their X-ray diffraction patterns remain unchanged even after 4 h of water immersion. UV/vis absorption spectrum shows that C6H4NH2CuBr2I compound has an excellent optical absorption over the entire visible spectrum. We applied this copper-based light absorber in printable mesoscopic solar cell for the initial trial and achieved a power conversion efficiency of ∼0.5%. Our study represents an alternative pathway to develop low-toxic and highly stable organic-inorganic hybrid materials for photovoltaic application.

A ferroelectric tunnel junction based on the piezoelectric effect for non-volatile nanoferroelectric devices

A ferroelectric tunnel junction based on the piezoelectric effect mechanism, which not only overcomes the drawbacks concerning retention time and polarization switching in the ferroelectric tunnel junction based on the electrostatic effect, but also suggests a new design concept for compact ferroelectric tunnel junction solid-state memories for next-generation information technology devices.