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Chain Vacancies in 2D Crystals
Author(s) -
Zhao Jiong,
Nam Honggi,
Ly Thuc Hue,
Yun Seok Joon,
Kim Sera,
Cho Suyeon,
Yang Heejun,
Lee Young Hee
Publication year - 2017
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201601930
Subject(s) - vacancy defect , materials science , condensed matter physics , van der waals force , stacking , semiconductor , chemical physics , grain boundary , crystallographic defect , density functional theory , crystallography , computational chemistry , chemistry , optoelectronics , microstructure , physics , organic chemistry , molecule , metallurgy
Defects in bulk crystals can be classified into vacancies, interstitials, grain boundaries, stacking faults, dislocations, and so forth. In particular, the vacancy in semiconductors is a primary defect that governs electrical transport. Concentration of vacancies depends mainly on the growth conditions. Individual vacancies instead of aggregated vacancies are usually energetically more favorable at room temperature because of the entropy contribution. This phenomenon is not guaranteed in van der Waals 2D materials due to the reduced dimensionality (reduced entropy). Here, it is reported that the 1D connected/aggregated vacancies are energetically stable at room temperature. Transmission electron microscopy observations demonstrate the preferential alignment direction of the vacancy chains varies in different 2D crystals: MoS 2 and WS 2 prefer 〈 2 ¯ 11 〉 direction, while MoTe 2 prefers 〈 1 ¯ 10 〉 direction. This difference is mainly caused by the different strain effect near the chalcogen vacancies. Black phosphorous also exhibits directional double‐chain vacancies along 〈01〉 direction. Density functional theory calculations predict that the chain vacancies act as extended gap (conductive) states. The observation of the chain vacancies in 2D crystals directly explains the origin of n‐type behavior in MoTe 2 devices in recent experiments and offers new opportunities for electronic structure engineering with various 2D materials.