Chun-lian Hu

Intensity and profile manifestation of resonant Raman behavior of carbon nanotubes

natl lab superlattices & microstruct, beijing 100083, peoples r china. chinese acad sci, inst met res, shenyang 110015, peoples r china.;tan, ph (reprint author), natl lab superlattices & microstruct, pob 912, beijing 100083, peoples r china

A theoretical study on the transport property of the La0.7Sr0.3MnO3/Si p-n heterojunction

The transport property of the La0.7Sr03MnO3/Si heterostructure was investigated theoretically by applying the drift-diffusion model to the present system. A simple scenario of the semiconductor band and electric field at the interface region of the heterostructure with various bias voltages are presented. The good agreement between the self-consistent calculated results and the experimental data indicates that the proposed band picture is valid for the interpretation of the transport property of the p-n heterojunctions made of La0.7Sr0.3MnO3 and Si regardless of the complexity of the interface structures and multi-couplings among charge, spin, lattice and orbital of manganites.

Mode splitting in photoluminescence spectra of a quantum-dot-embedded microcavity

A microcavity structure, containing self-assembled InGaAs quantum dots, is studied by angle-resolved photoluminescence (PL) spectroscopy. A doublet with the splitting energy of 0.5–1.5 nm appears when the detection angle is larger than 35°. This doublet is identified as mode splitting (not the Rabi splitting) by polarization measurements. We find that it is the considerable deviation of the cavity-mode frequency from the central frequency of the stop band that makes the TE and TM cavity modes split more discernibly. The inhomogeneous broadening of quantum dots gives the TE and TM cavity modes a chance to show up simultaneously in the PL spectra.

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.

Theoretical study on the transport property of p-Si∕n-SrTiO3−δ

The transport property of p-Si∕n-SrTiO3−δ heterojunction has been obtained self-consistently with the drift-diffusion model at the temperature range from 200to300K by applying Richardson current at the interface. The band structures, electric field intensities, and carrier distributions at various bias voltages or temperatures are obtained from our calculation. Furthermore, the evolution of the I-V behavior with the temperature is also obtained theoretically. From the good agreement between our calculated results and the experimental data, we can conclude that the rectification property in the perovskite-silicon p-n junction is owing to the drift-diffusion mechanism and the transport property of Si substrate significantly contributes to the almost linear characteristic of the I-V curves.

Experimental measurement of microwave-induced electron spin-flip time

The electron spin resonance (ESR) is optically detected by monitoring the microwave-induced changes in the circular polarization of the neutral exciton (X) and the negatively charged exciton (X-) emission in CdTe quantum wells with low density of excess electrons. We find that the circular polarization of the X and X- emission is a mapping of the spin polarization of excess electrons. By analyzing the ESR-induced decrease in the circular polarization degree of the X emission, we deduce the microwave-induced electron spin-flip time >0.1 mus, which is much longer than the recombination time of X and X-. This demonstrates that the optically detected ESR in type I quantum wells with low density of excess electrons does not obey the prerequisite for the conventional optically detected magnetic resonance

Theoretical simulation on the variation in the transport behavior under pressure and magnetic field in La0.825Sr0.175MnO3

Based on phase separation model and breadth-first traversal algorithm, the spin-related electron transport property of La0.825Sr0.175MnO3 under hydrostatical pressure and magnetic field was systematically simulated. We find that the external hydrostatical pressure has a more important influence on the residual resistivity, high temperature resistivity coefficient, activation energy, and electron scattering of La0.825Sr0.175MnO3 than the external magnetic field. However, the Curie temperature and the magnon scattering are more sensitive to the external magnetic field than to the external hydrostatical pressure in La0.825Sr0.175MnO3.

Studies on the cluster sizes in the mixed-phase thin films

Based on the phase separation scenario, by simulating the resistivity of La0.33Pr0.34Ca0.33MnO3 film with the known coexisting-phase sizes, the authors have obtained the theoretical ferromagnetic (FM) cluster sizes of La2∕3Ca1∕3MnO3 film, showing around 0.6μm near Tc. Subsequently the insulator-metal transition occurs when the cluster grows up to 0.7μm, and the abrupt drop in resistivity occurs when the size is around 0.9μm. Furthermore, the FM cluster sizes grow with the magnetic field. The obtained results indicate that the model and method can be used to predict the critical size of the clusters at the phase transition for the mixed-phase materials.

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)