Wing Waylin J, Sadeghi Seyed M, Gutha Rithvik R
Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899, United States of America.
J Phys Condens Matter. 2017 Jul 26;29(29):295301. doi: 10.1088/1361-648X/aa74ff. Epub 2017 Jun 12.
We report on the ultrafast decay of quantum dots that reaches nearly 430 ps without reduction in the emission intensity when near a metasubstrate of simple geometry. By implementing a layered structure of amorphous silicon sandwiched between two gold layers, the balance between plasmonic near field enhancement and energy transfer of the quantum dots has been shifted. This is achieved by tailoring the amount of Förster resonance energy transfer (FRET) to the top Au layer and plasmonic near field enhancement by the bottom Au layer. We also study the impact of deposition of Al oxide on the top Au layer, forming a charge barrier junction that can suppress Auger recombination of quantum dots. The results show that such a barrier can increase emission efficiency of the metastructure without significant reduction in the decay rate. We study the impact of formation of small nanoislands to contiguous islands via variation of the thickness of the top Au layer, and discuss how such morphologies determine the amount of FRET, screening of plasmonic field from the bottom Au layer, and enhancement of emission due to their own plasmonic fields.
我们报道了量子点的超快衰减，当靠近简单几何形状的超颖基底时，其衰减时间接近430皮秒，且发射强度无降低。通过实现夹在两个金层之间的非晶硅层状结构，量子点的等离子体近场增强与能量转移之间的平衡发生了改变。这是通过调整到顶部金层的福斯特共振能量转移（FRET）量以及底部金层的等离子体近场增强来实现的。我们还研究了在顶部金层上沉积氧化铝的影响，形成了一个电荷阻挡结，该结可以抑制量子点的俄歇复合。结果表明，这样的阻挡层可以提高亚结构的发射效率，而衰减率没有显著降低。我们通过改变顶部金层的厚度研究了从小纳米岛到连续岛的形成影响，并讨论了这种形态如何决定FRET的量、底部金层等离子体场的屏蔽以及由于其自身等离子体场导致的发射增强。
