Dynamics and Removal Pathway of Edge Dislocations in Imperfectly Attached PbTe Nanocrystal Pairs: Toward Design Rules for Oriented Attachment

Abstract

Using in situ high-resolution TEM, we study the structure and dynamics of well-defined edge dislocations in imperfectly attached PbTe nanocrystals. We identify that attachment of PbTe nanocrystals on both {100} and {110} facets gives rise to b = a/2⟨110⟩ edge dislocations. Based on the Burgers vector of individual dislocations, we can identify the glide plane of the dislocations. We observe that defects in particles attached on {100} facets have glide planes that quickly intersect the surface, and HRTEM movies show that the defects follow the glide plane to the surface. For {110} attached particles, the glide plane is collinear with the attachment direction, which does not provide an easy path for the dislocation to reach the surface. Indeed, HRTEM movies of dislocations for {110} attached particles show that defect removal is much slower. Further, we observe conversion from pure edge dislocations in imperfectly attached particles to dislocations with mixed edge and screw character, which has important implications for crystal growth. Finally, we observe that dislocations initially closer to the surface have a higher speed of removal, consistent with the strong dislocation free surface attractive force. Our results provide important design rules for defect-free attachment of preformed nanocrystals into epitaxial assemblies.

Resilient Pathways to Atomic Attachment of Quantum Dot Dimers and Artificial Solids from Faceted CdSe Quantum Dot Building Blocks

“…These findings clearly highlight the importance of the orientation of the glide plane relative to the surface for edge dislocation removal and are consistent with our previous observations in PbTe. 55 We also observed situations where multiple dislocations formed at the interface of {11 � 00} and {112 � 0} terminated particles shown in Figures 6A, B Figure 6A) which show a complicated geometry. Figure 6B shows the detailed structure near the dislocation cores.…”

“…In these materials, attachment can be induced by heating NC superlattices on a liquid subphase, 34 heating in high vacuum, 77 chemical treatments to remove the organic ligands, 28,29,78 or diluting the particles to desorb surface bound ligands. 55 Ondry et. al.…”

“…In Figure 6J, the dislocation removal speed, which we defined as the distance the dislocation had to move to be removed divided by the time it takes for removal, is shown for many different trajectories in each defect category. Because dislocation surface attractive forces can have an effect on the kinetics, 55 we differentiate the initial distance the dislocation was from the surface by the color of the point on the graph. In this plot, the full circles indicate that the dislocations were removed during the observation time and the open circles indicate that the dislocations were not successfully removed from the interface, thus, giving an upper bound for the dislocation removal speed.…”

Hybrid Growth Modes of PbSe Nanocrystals with Oriented Attachment and Grain Boundary Migration

“…[15,16] Since NCs with different growth modes normally show different physical and chemical properties, detailed investigations on NCs growth processes may help better understand the phase transformation and the underlying growth mechanisms. [18] Oriented attachment mainly consists of the following three steps: (1) adjacent particles spontaneously self-organize so that they share a common crystallographic orientation; (2) the particles fuse to create a planar coherent interface; (3) the primary particles are perfectly aligned during growth, [14,19] as implied by the diffraction of a single crystal structure. [18] Oriented attachment mainly consists of the following three steps: (1) adjacent particles spontaneously self-organize so that they share a common crystallographic orientation; (2) the particles fuse to create a planar coherent interface; (3) the primary particles are perfectly aligned during growth, [14,19] as implied by the diffraction of a single crystal structure.…”

Unravelling three-dimensional adsorption geometries of PbSe nanocrystal monolayers at a liquid-air interface

“…At which moment in the process is there a bifurcation toward either a square or a honeycomb geometry, and which factors decide the geometry? Which factors determine the amount of disorder on both atomic and NC length scales and how can we reduce this 10,[15][16][17][18][19][20][21] ? A recently introduced simulation model to predict the self-assembly of NCs at fluid-fluid interfaces provided fundamental insights that will help to answer these questions 22,23 .…”