Study the Ultrafast Dynamics of Superconductor and Semiconductor by Femtosecond Pump-Probe Technique

• Main Authors: Chao. Shyu-Chin, 趙世清
• Other Authors: Wu, Kaung-Hsiung
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/46353512645886153730

碩士 === 國立交通大學 === 電子物理系 === 85 === We have set up a home-made femtosecond passively mode-locked Ti:sapphire laser and a room-temperature pump-probe measurement system to measure the transient reflectivity of the YBCO superconductor thin film with different oxygen contents and arsenic-ion-implanted GaAs thin films with different implantation and annealing conditions. The dependence of transient differential reflectivity (ΔR/R) on probing photon energy and oxygen contents of oxygen stoichiometric YBCO films was determined by using femtosecond pump-probe measurement at probing energy ranging from 1.45 eV to 1.65 eV. Experimental results reveal that the strength of carrier-phonon coupling decreases with decreasing oxygen content, and the Fermi level for the partially oxygen-deficient YBCO, film with x=6.68 is located at least 1.5 eV above the Cu d9/d10 band in the CuO2 plane. The carrier lifetime of arsenic-ion-implanted GaAs demonstrated was found to increase as the dosage decreases or annealing temperature increases from 200℃ up to 800℃. A sign reversal of the reflecive index change at annealing temperatures 500∼-600℃ was observed, this phenomenon can be partially explained by the shrinkage of bandgap energy during implantation and recovery during thermal annealing.