Leng Liao

Dember effect induced photovoltage in perovskite p-n heterojunctions

An unusual and rather large transient lateral photovoltage (LPV) has been observed in La0.9Sr0.1MnO3∕SrNb0.01Ti0.99O3 and La0.7Sr0.3MnO3∕Si heterojunctions under the nonuniform irradiation of pulsed laser. The irreversible LPVs on both sides of a p-n junction challenge the well established model for LPV in conventional semiconductor p-n junctions, which can be well explained by the Dember effect. Much larger LPV is observed in La0.7Sr0.3MnO3∕Si than that in La0.9Sr0.1MnO3∕SrNb0.01Ti0.99O3. Similar results measured from both substrates of SrNb0.01Ti0.99O3 and Si also support such a Dember effect. Much larger LPVs in heterojunctions than those in simple samples (SrNb0.01Ti0.99O3 or Si) suggest a potential application of Dember effect in heterostructures.

In situ probing mechanical properties of individual tungsten oxide nanowires directly grown on tungsten tips inside transmission electron microscope

The mechanical properties of individual tungsten oxide (WO3) nanowires, directly grown onto tungsten scanning tunneling microscopy tips, have been investigated by a custom-built in situ transmission electron microscopy (TEM) measurement system. Young’s modulii (E) of the individual WO3 nanowires were measured with the assistance of electric-induced mechanical resonance. The results indicate that E basically keeps constant at diameter larger than 30nm, while it largely increases with decreasing diameter when diameter becomes smaller than 30nm. This diameter dependence is attributed to the lower defect density in nanowires with smaller diameter, as imaged by in situ TEM.

A theoretical study on the dynamic process of the lateral photovoltage in perovskite oxide heterostructures

The lateral photovoltaic process on the La0.9Sr0.1MnO3 /SrNb0.01Ti0.99O3 heterostructure is revealed by solving time-dependent drift-diffusion equations in a two dimensional scenario. We find that both the conventional lateral photovoltage LPV effect and the Dember effect contribute to the LPV. Under a low irradiation, the conventional LPV process plays a main role in the lateral photovoltaic process. With the laser pulse energy large enough, the Dember process becomes dominant. Due to the competition between Dember and conventional lateral photovoltage, a laterally modulated photovoltage can be obtained theoretically on the n-type side of the heterostructure.

The effect of phase separation on the temperature dependent magnetoresistance in perovskite oxide heterojunction

The interesting behavior of the magnetoresistance at various temperatures for the heterojunction of La0.9Sr0.1MnO3∕SrNb0.01Ti0.99O3 is well explained based on the phase separation scenario. The good agreement between the theoretical and experimental results reveals that the mechanism for the variation in magnetoresistance with temperature and with the magnetic field is the competition between the positive magnetoresistance in the paramagnetic phase caused by the interface effect of the La0.9Sr0.1MnO3∕SrNb0.01Ti0.99O3 p-n heterojunction and the negative magnetoresistance in the ferromagnetic phase of the La0.9Sr0.1MnO3 film, respectively.

Large-scale aligned silicon carbonitride nanotube arrays : Synthesis, characterization, and field emission property

Large-scale aligned silicon carbonitride (SiCN) nanotube arrays have been synthesized by microwave-plasma-assisted chemical vapor deposition using SiH4, CH4, and N2 as precursors. The three elements of Si, C, and N are chemically bonded with each other and the nanotube composition can be adjusted by varying the SiH4 concentration, as revealed by electron energy loss spectroscopy and x-ray photoelectron spectroscopy. The evolution of microstructure of the SiCN nanotubes with different Si concentrations was characterized by high-resolution transmission electron microscopy and Raman spectroscopy. The dependence of field emission characteristics of the SiCN nanotubes on the composition has been investigated. With the increasing Si concentration, the SiCN nanotube exhibits more favorable oxidation resistance, which suggests that SiCN nanotube is a promising candidate as stable field emitter.

A numerical design of opto-thermionic refrigeration with perovskite oxide heterostructures

Opto-thermionic refrigeration is an environment-friendly method. To improve the opto-thermionic refrigeration efficiency, a system with a perovskite oxide multilayer of p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 is proposed based on the model of opto-thermionic refrigeration. Because the Auger coefficient of SrTiO3 is two orders smaller than that of GaAs, the calculated refrigeration power of the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 system is much higher than that of the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system. A refrigeration power of as high as 39 Wc m −2 is obtained numerically in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 system, which suggests a potential application of the oxide structures in opto-thermionic refrigeration. (Some figures in this article are in colour only in the electronic version)