二维外延量子点超晶格的化学触发形成,ACS Nano

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二维外延量子点超晶格的化学触发形成
ACS Nano ( IF 15.8 ) Pub Date : 2016-07-14 00:00:00 , DOI: 10.1021/acsnano.6b02562
Willem Walravens , Jonathan De Roo , Emile Drijvers , Stephanie ten Brinck ₁ , Eduardo Solano , Jolien Dendooven , Christophe Detavernier , Ivan Infante ₁ , Zeger Hens

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外延连接的量子点的二维超晶格使尺寸量化效应与高电荷载流子迁移率结合在一起，这是基于电荷传输的高性能QD器件的必要先决条件。在这里，我们证明已知可恢复纳米晶体化学计量的表面活性添加剂可触发PbSe和PbS量子点外延超晶格的形成。更具体地说，我们表明，同时添加硫族元素（硫化钠）和取代油酸铅（胺）的添加剂均可诱发PbSe量子点的小面积外延超晶格。在后一种情况下，胺的碱度是调节超晶格对称性的灵敏手柄，强碱和弱碱分别产生伪六边形或准正方形晶格。通过密度泛函理论计算和通过核磁共振波谱监测的原位滴定，我们将此观察结果与胺的不同配位焓和配体置换潜能相联系。紧接着，在单层形成之前，初始配体密度降低了约10％，并加入了温和的，油酸铅取代的化学触发物（如苯胺），证明了诱导长方型微米级方形超晶格的关键。量子点越大，效果越明显。由于该方法也适用于PbS量子点，因此我们得出结论，它为形成高度有序的外延量子点超晶格提供了一种可再现且合理的方法。

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Chemically Triggered Formation of Two-Dimensional Epitaxial Quantum Dot Superlattices

Two dimensional superlattices of epitaxially connected quantum dots enable size-quantization effects to be combined with high charge carrier mobilities, an essential prerequisite for highly performing QD devices based on charge transport. Here, we demonstrate that surface active additives known to restore nanocrystal stoichiometry can trigger the formation of epitaxial superlattices of PbSe and PbS quantum dots. More specifically, we show that both chalcogen-adding (sodium sulfide) and lead oleate displacing (amines) additives induce small area epitaxial superlattices of PbSe quantum dots. In the latter case, the amine basicity is a sensitive handle to tune the superlattice symmetry, with strong and weak bases yielding pseudohexagonal or quasi-square lattices, respectively. Through density functional theory calculations and in situ titrations monitored by nuclear magnetic resonance spectroscopy, we link this observation to the concomitantly different coordination enthalpy and ligand displacement potency of the amine. Next to that, an initial ∼10% reduction of the initial ligand density prior to monolayer formation and addition of a mild, lead oleate displacing chemical trigger such as aniline proved key to induce square superlattices with long-range, square micrometer order; an effect that is the more pronounced the larger the quantum dots. Because the approach applies to PbS quantum dots as well, we conclude that it offers a reproducible and rational method for the formation of highly ordered epitaxial quantum dot superlattices.

更新日期：2016-07-14

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