Structural and decomposition characteristics of threading dislocations in single-crystal diamond observed via TEM

Abstract

High threading dislocation (TD) density is a critical impediment to diamond applications in ultra-wide bandgap semiconductors. The proliferation of threading dislocations (TDs) during single-crystal diamond growth arises from atomic-scale mismatches, dislocation dissociation, and dislocation extension from stacking fault (SF) termini. This work employs etch pit analysis and transmission electron microscopy to investigate dislocation propagation pathways and primarily reveals the microscopic mechanisms of dislocation dissociation and bending in the near-surface region of diamond. A phenomenon of “periodic contrast” within the dislocation bundle was discovered, and its physical origin elucidated. The clear dissociation into Shockley partial dislocations and the formation of an intrinsic stacking fault between them were unambiguously observed. This directly reveals the dissociation mechanism of the dislocation bundle under specific conditions, whereas previous studies primarily focused on its macroscopic formation as an integral structure. Results demonstrate that chemical vapor deposition on (100)-oriented substrates predominantly yields dislocation bundles aligned nearly parallel to the [001] growth direction. Dislocation line decomposition into bundles near the sample surface was observed, originating from SF termini with resultant Burgers vectors b = a/6[2 1¯1¯] and a/6[11 2¯].