| Summary: | 碩士 === 中原大學 === 應用物理研究所 === 96 === 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.
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