氧化鋅晶粒大小及氧化鎂鋅之鎂含量對激子-縱模光聲子作用的影響

Abstract

利用量測由溶膠－凝膠製成不同晶粒大小的氧化鋅及不同鎂含量（0<x<0.05）氧化鎂鋅粉末（MgxZn1−xO）的變溫螢光光譜，可以得到激子－縱模光聲子（LO-phonon）之間耦合的關係。在氧化鋅量子點系統中不明顯激子的縱模光聲子映稱（LO-phonon replicas），以及較小的13 K至 300 K激子能量差顯示激子－縱模光聲子耦合強度的降低。從氧化鋅量子點系統及氧化鎂鋅粉末激子游離能的變大可得知激子波耳半徑的變小。這個結果將導致激子結構極性降低，以致於當氧化鋅量子點縮小及氧化鎂鋅中鎂含量增加，激子－縱模光聲子的交互作用將隨之減弱。

The coupling between exciton and longitudinal optical (LO) phonon was investigated by using of the temperature-dependent photoluminescence from various sizes of ZnO grain and MgxZn1−xO powders in the range of 0<x<0.05 prepared by sol-gel synthesis. The unapparent LO-phonon replicas of free exciton emission in ZnO quantum dots (QDs) system and the smaller free exciton energy difference between 13 K and 300 K reveal decreasing weighting of exciton□LO phonon coupling strength. From ZnO QDs system and MgxZn1-xO powders, the increase of the exciton binding energy resulting from the decrease of the exciton Bohr radius makes the exciton less polar that is responsible for reducing the coupling strength of exciton-LO phonon as shrinking ZnO QDs size and increasing Mg content.