Abstract
Soon after the discovery of LaO1-xFxFeAs with Tc ~26 K, the TC of iron-based superconductor was quickly increased up to 56 K. FeSe1-x, having the simplest crystal structure among iron based superconductors, was reported with superconducting transition around 8 K. The simple structure of FeSe-superconductors might provide important clues to the mechanism of superconductivity in iron-based superconductors. In this thesis, the transport properties of FeSe1-xTex films, including resistivity, Hall effect, magnetoresistance, and current-voltage (I-V) characteristics in superconducting state, will be presented. The Tc of FeSe1-xTex thin film is suppressed seriously in low substituted samples, which is found to be closely associated with the confinement of structural distortion at low temperature. The Hall coefficient of FeSe1-xTex thin films has strong temperature dependence and can be described by two-band model. The magnetoresistance evolves from positive to negative gradually as the Te substitution level increases. Combine with the resistivity and Hall effect results, the negative magnetoresistance in higher Te substituted samples is attributed to the weak localization effect. The vortex state of FeSe-superconductors was investigated with the I-V characteristics of FeSe1-xTex thin films. A vortex liquid-glass transition and the scaling properties of I-V curves were observed in higher Te substituted samples, indicating the existence of vortex-glass state.