利用時間與空間解析飛秒光譜研究位能差調變非平衡態熱電放大元件之超快動力學

Abstract

本論文以時間解析飛秒光譜研究位能差調變非平衡態熱電放大元件(PANTEC)之超快動力學，藉由瞬時反射率變化得到PANTEC的電子溫度。理論預測PANTEC的高低電子濃度摻雜界面處存在電子與聲子溫度的非平衡現象，藉由時間解析激發-探測顯微儀，我們能在固定溫度梯度的PANTEC上進行不同位置的時間解析光譜量測，由時間解析光譜中的電子能量弛緩時間與振盪訊號，進而證實在位能差調變非平衡態熱電放大元件中電子溫度與聲子溫度的非平衡現象。 此外，我們亦利用時間與空間解析飛秒光譜研究微米級鎳平板線之超快動力學。鎳平板線的自旋-晶格能量弛緩時間可由瞬時反射率的變化得到，隨著線寬的增加，自旋-晶格能量弛緩時間也隨之增加。這顯示微米級鎳平板線的磁性動力學行為與尺寸有密切的關連性。

In this dissertation, we used time-resolved femtosecond spectroscopy to study the ultrafast dynamics of Potential-step amplified non-equilibrium thermal-electric converters (PANTEC). The electron temperature in PANTEC can be estimated by the transient reflectivity changes at various temperature gradients. The nonequilibrium between electron and phonon temperatures around the junction interface of PANTEC structure has been predicted by theoretical calculations. In this study, we measured the spatial distribution of ultrafast dynamics of electrons by time-resolved pump-probe microscope. According to the transient reflectivity changes, the nonequilibrium phenomenon between electron and phonon temperatures around the junction interface of PANTEC structure was clearly observed through the relaxation time of hot electrons and the oscillation signal in transient reflectivity changes. Moreover, we also studied the ultrafast dynamics of Ni micro planar wires which were prepared by e-beam lithography using time-resolved pump-probe microscope. The relaxation time associated with the spin-lattice relaxation in transient reflectivity changes is size- and geometric-structure dependent. The spin-lattice relaxation time increases with increasing the width of Ni micro planar wires, which shows the close relation between the relaxation of magnetic moments and the geometric structure of Ni micro planar wires.