氧原子對自聚性硒化鎘量子點的影響之研究

Influence of atomic oxygen on self-assembled CdSe quantum dots

劉睦駕(Mu-Jia Liou)

指導教授 ： 王智祥

中原大學/理學院/應用物理研究所/碩士(2008年)

https://doi.org/10.6840/cycu200800293

摘要

運用電漿輔助式分子束磊晶系統在硒化鋅緩衝層上成長硒化鎘自聚性量子點，並分別利用原子力顯微鏡觀察其表面形貌變化及透過光激螢光光譜了解樣品的光學特性。我們首先探討氧原子對於硒化鎘量子點ripen機制的影響，從光激螢光光譜顯示4.4原子層的硒化鎘量子點峰值能量不隨量子點成長完後停留在成長腔中的時間增加而有所變異，代表量子點在真空腔中不會有ripen的行為，即使在260度的成長溫度下也是一樣；然而，先在硒化鋅緩衝層表面鋪上氧原子的2.7原子層的硒化鎘量子點，發現量子點峰值能量隨著量子點成長完後停留時間增加而有逐漸紅位移的趨勢。從我們的結果顯示出氧原子可能是導致ripen效應的原因，所以隨著量子點成長完後停留的時間愈久，量子點的尺寸會增加。此外，我們分別探討2.7與4.4原子層的硒化鎘量子點的ripen效應與氧原子含量的關係。針對4.4原子層的硒化鎘量子點，發現鋪極少量的氧原子時，其量子點峰值能量呈現藍位移，代表此少量的氧原子增加了成核的密度，導致量子點尺寸變小。然後，進一步地增加氧原子的含量，其量子點峰值能量呈現紅位移，可能是由於氧原子提升了ripen效應或是變成三元的材料而有能帶彎曲的效應。

關鍵字

氧原子對量子點的影響

並列摘要

Self-assembled CdSe quantum dots (QDs) have been grown on ZnSe buffer layers by using plasma-assisted molecular beam epitaxy. Atomic force microscopy (AFM) and photoluminescence (PL) were employed to study the surface morphology and optical properties of CdSe QDs, respectively. First of all we investigated the effect of atomic oxygen on the ripening of the CdSe QDs. The PL peak energy of the 4.4 mono-layers (MLs) ripen mode CdSe QDs was independent of the time of growth interruption (G. I.) indicating that the ripen mode CdSe QDs have no the ripening behavior in the vacuum chamber even though at the growth temperature of 260 ℃. However, the PL peak energy of 2.7 MLs S-K mode CdSe QDs which were prior deposited the atomic oxygen on the surface of ZnSe buffer layers was gradually red shift as the time of growth interruption increased . Our results show that the ripening could be induced by the atomic oxygen, and the size of QDs was increased as the interruption time increased. Moreover, the ripening depend on the amount of atomic oxygen has been also investigated for the 2.7 and 4.4 MLs QDs respectively. For the 4.4 MLs QDs, the PL peak energy of the sample which had the smallest amount of oxygen showed a significant blue shift indicating that a small amount of atomic oxygen could increase the nucleation density and lead the size of QDs decreased. Then, the PL peak energy became red shift as the amount of oxygen increased further. This is probably due to the enhancement of ripening and/or the band-gap bowing effect of the ternary materials.

並列關鍵字

Influence of atomic oxygen on self-assembled

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