Shoushan Fan

Effect of defects on optical phonon Raman spectra in SiC nanorods

Fabricated one-dimensional (1D) materials often have abundant structural defects. Experimental observation and numerical calculation indicate that the broken translation symmetry due to structural defects may play a more important role than the quantum confinement effect in the Raman features of optical phonons in polar semiconductor quantum wires such as SiC nanorods, (C) 1999 Elsevier Science Ltd. All rights reserved.

Influences of substrates and substrate temperatures on characteristics of epitaxial La0.5Sr0.5CoO3 thin films

Abstract Epitaxial growth of La 0.5 Sr 0.5 CoO 3 (LSCO) film has been achieved by pulsed laser deposition. Widely used substrates, MgO, SrTiO 3 and LaAlO 3 were chosen to examine the effect of the substrates on the growth of LSCO films. The influence of the substrate temperatures ( T s ) on the characteristics of the LSCO films was studied in a temperature range of 500–850°C. The LSCO films deposited at substrate temperatures of T s =800–850°C show good epitaxial features, better than that of the films deposited at lower T s . The experimental results reveal that the lattice mismatch and the difference of the expansion coefficients between the substrates and the LSCO films are important in the growth process of the LSCO films.

Effect of changing incident wavelength on Raman features of optical phonons in SiC nanorods and TaC nanowires

Novel Raman scattering in polar semiconductor SiC and TaC one-dimensional materials have been carried out. With increasing incident laser wavelength from 488 to 633 nm there is a huge difference in Raman intensity enhancement for the LO/IF peaks and the TO peak. This has been interpreted as due to Frohlich interaction and abundant defects in polar nano-scale semiconductor materials.

Structural characteristics and the control of crystallographic orientation of CeO2 thin films prepared by laser ablation

Abstract CeO2 thin films were grown on (1xa00xa00) silicon substrates by pulsed laser deposition. X-ray diffraction results indicated that fully (1xa01xa01) oriented and highly (1xa00xa00) oriented CeO2 films on Si (1xa00xa00) were achieved, respectively. Oxygen pressure was found to be important to control the crystallographic orientation. A possible mechanism was proposed to explain these results. Auger electron spectroscopy and Rutherford backscattering spectrometry analysis showed an uniform concentration distribution of Ce and O throughout the epitaxial layer independent of the oxygen pressure. The electrical properties of the films were characterized by capacitance–voltage measurements.

Epitaxial growth characteristics of oxide thin films prepared by pulsed laser deposition

Abstract Some unique characteristics of epitaxial growth of oxide thin films prepared by pulsed laser deposition have been observed in this study. The study demonstrates that deposition temperature is one of the most important parameters in controlling orientation and epitaxial growth of oxide thin films. Higher temperature is usually imperative for the epitaxial growth. The threshold temperature for epitaxial growth of oxide film depends on the substrate materials, which relate mainly to the lattice mismatch and component similarity between the film and the substrate. A small lattice mismatch and a high component similarity are favorable to epitaxial growth and may decrease the epitaxial threshold temperature significantly. In addition, the orientation of CeO 2 film, grown on Si substrate, possess a unique dependence on ambient oxygen pressure, which demonstrates the significant influence of oxygen pressure to the epitaxial orientation of oxide thin films.

Growth of ferroelectric (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 thin films by fulsed laser deposition

Abstract Growth of (K 0.5 Na 0.5 ) 0.2 (Sr 0.75 Ba 0.25 ) 0.9 Nb 2 O 6 (KNSBN) films on (0 0 1) MgO substrates and on (0 0 1) oriented La 0.5 Sr 0.5 CoO 3 (LSCO) layers by pulsed laser deposition has been studied. X-ray diffraction θ–2θ scans indicated that the KNSBN films were of c -axis orientation. X-ray Phi scans on the (2 2 1) reflection revealed that the films grown on the MgO substrates were epitaxial growth with two [1 0 0]KNSBN in-plane orientation rotating about ±18° with respect to [1 0 0]MgO. Sandwich structures of KNSBN films with LSCO as top and bottom electrodes have been performed on (0 0 1)LaAlO 3 (LAO) substrates. The measurements of the ferroelectricity of the as-grown film gave hysterisis loop with the remnant polarization of P r ∼ 8 μ C cm −2 and the coercive field of E c ∼ 55 KV cm −1 .

Epitaxial growth and electrical transport properties of La0.5Sr0.5Co03 thin films prepared by pulsed laser deposition

Epitaxial growth of the La0.5Sr0.53(LO) thin films has been realized on Lin3, SrTiC3 and MgO substrates by pulsed laser deposition. The epitaxial growth behavior and the electrical transport properties of these films were studied systematically. The temperature dependencies of the resistivity of the film have been determined. Studies indicate that close dependencies exist between the crystal structures and the electrical transport properties of the epitaxial LSCO films, and that the epitaxial thin films are of low resistivity and metallic conductive features. The epitaxial films deposited on the LaA103 substrates at about 700 °C possess the optimal properties compared with the others. Discussions of the dependencies and the mechanisms of the epitaxial structures on the electrical transport properties of the LSCO films have been made.