Ondry Justin C, Philbin John P, Lostica Michael, Rabani Eran, Alivisatos A Paul
Department of Chemistry , University of California , Berkeley , California 94720 , United States.
Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
ACS Nano. 2019 Nov 26;13(11):12322-12344. doi: 10.1021/acsnano.9b03052. Epub 2019 Jul 2.
The goal of this work is to identify favored pathways for preparation of defect-resilient attached wurtzite CdX (X = S, Se, Te) nanocrystals. We seek guidelines for oriented attachment of faceted nanocrystals that are most likely to yield pairs of nanocrystals with either few or no electronic defects or electronic defects that are in and of themselves desirable and stable. Using a combination of high-resolution transmission electron microscopy (HRTEM) and electronic structure calculations, we evaluate the relative merits of atomic attachment of wurtzite CdSe nanocrystals on the {11̅00} or {112̅0} family of facets. Pairwise attachment on either facet can lead to perfect interfaces, provided the nanocrystal facets are perfectly flat and the angles between the nanocrystals can adjust during the assembly. Considering defective attachment, we observe for {11̅00} facet attachment that only one type of edge dislocation forms, creating deep hole traps. For {112̅0} facet attachment, we observe that four distinct types of extended defects form, some of which lead to deep hole traps whereas others only to shallow hole traps. HRTEM movies of the dislocation dynamics show that dislocations at {11̅00} interfaces can be removed, albeit slowly. Whereas only some extended defects at {112̅0} interfaces could be removed, others were trapped at the interface. Based on these insights, we identify the most resilient pathways to atomic attachment of pairs of wurtzite CdX nanocrystals and consider how these insights can translate to the creation of electronically useful materials from quantum dots with other crystal structures.
这项工作的目标是确定制备具有缺陷抗性的附着纤锌矿CdX（X = S、Se、Te）纳米晶体的有利途径。我们寻求有关多面纳米晶体定向附着的指导原则，这些纳米晶体最有可能产生具有很少或没有电子缺陷的纳米晶体对，或者产生本身就理想且稳定的电子缺陷。通过结合高分辨率透射电子显微镜（HRTEM）和电子结构计算，我们评估了纤锌矿CdSe纳米晶体在{11̅00}或{112̅0}面族上原子附着的相对优点。只要纳米晶体面完全平坦且纳米晶体之间的角度在组装过程中可以调整，在任何一个面上的成对附着都可以导致完美的界面。考虑到有缺陷的附着，我们观察到对于{11̅00}面附着，只形成一种类型的边缘位错，产生深孔陷阱。对于{112̅0}面附着，我们观察到形成四种不同类型的扩展缺陷，其中一些导致深孔陷阱，而另一些只导致浅孔陷阱。位错动力学的HRTEM电影显示，{11̅00}界面处的位错可以被去除，尽管速度很慢。而{112̅0}界面处只有一些扩展缺陷可以被去除，其他缺陷被困在界面处。基于这些见解，我们确定了纤锌矿CdX纳米晶体对原子附着的最具抗性的途径，并考虑这些见解如何转化为从具有其他晶体结构的量子点创造电子有用材料。
