氧化鈦奈米顆粒/氧化鋅奈米柱複合材料之雷射光學性質研究

Abstract

本篇論文的主要研究在於製備氧化鋅奈米柱與氧化鈦奈米顆粒此一新穎的半導體複合材料，並探討其在光脈衝激發下所展現的隨機雷射(Random laser)特性。我們發現，在氧化鈦奈米顆粒的幫助下，氧化鋅奈米柱於紫外波段所擁有的雷射光強度能夠被顯著地增強。其主要原因，來自於二者材料間的導、價帶位置不同， 靠著螢光共振而伴隨的能量傳遞(Fluorescence Resonance EnergyTransfer)，半導體內部的載子(Carrier)遷移能夠成功地增強氧化鋅奈米柱的同調輻射(Stimulated Emission)。除此之外，氧化鈦奈米顆粒與生俱來的高折射係數(refractive index)(n~2.5)，可使其完美地散射由氧化鋅奈米柱產生的紫外輻射，進一步增強在多重性散射下(Multiple Scattering)，系統所得到的同調回饋(Coherent Feedback)。

An improvement in random lasing action at ultraviolet wavelength has beenachieved from ZnO nanorod arrays grown on sapphire substrate with the assistance of TiO2 nanoparticles. Due to the inherent nature of high refractive index of TiO2 (n ~2.5)> ZnO(n~1.9), the TiO2 nanoparticles can serve efficiently as excellent nanoscatterers,which can promote the formation of closed-loop paths. In addition, the underlying origin of the pronounced lasing action can also be attributed to the enhanced emission arising from fluorescence resonance energy transfer (FRET) between the band edge transition of ZnO nanorods and TiO2 nanoparticles. The strategy of the lasing enhancement provided here should be very useful for the future development in designing high efficiency optoelectronic devices.