Chemically Triggered Formation of Two-Dimensional Epitaxial Quantum Dot Superlattices.
Chemically Triggered Formation of Two-Dimensional Epitaxial Quantum Dot Superlattices.
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DOI：
10.1021/acsnano.6b02562
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发表时间：
2016-07
期刊：
影响因子：
17.1
通讯作者：
W. Walravens;J. De Roo;Emile Drijvers;Stephanie ten Brinck;E. Solano;J. Dendooven;C. Detavernier;I. Infante;Z. Hens
中科院分区：
文献类型：
--
作者：
W. Walravens;J. De Roo;Emile Drijvers;Stephanie ten Brinck;E. Solano;J. Dendooven;C. Detavernier;I. Infante;Z. Hens
外延连接的量子点的二维超晶格使得尺寸量子化效应能够与高电荷载流子迁移率相结合，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，我们证明了已知的表面活性添加剂恢复PbSe和PbS量子点的化学计量可以触发外延超晶格的形成。更具体地说，我们表明，硫族元素添加（硫化钠）和油酸铅置换（胺）添加剂诱导小面积外延超晶格的PbSe量子点。在后一种情况下，胺的碱性是一个敏感的处理，以调整超晶格的对称性，与强和弱基地产生伪六方或准正方形晶格，分别。通过密度泛函理论计算和原位滴定监测核磁共振光谱，我们将这一观察相伴随的不同的配位焓和配体置换的胺的效力。接下来，在单层形成之前初始配体密度的初始约10%的降低和添加温和的油酸铅置换化学触发剂（例如苯胺）被证明是诱导具有长程平方微米级的方形超晶格的关键;量子点越大，这种效果越明显。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重复且合理的方法。
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.