Scanning Tunneling Microscopy Examinations of the Effects of Defects on the Charge Density Wave Order in the Chemical Vapor Deposition-Derived TaSe2 on Au Foils

Defects are well known to obviouslyaffect the crystal structureand the electronic property of two-dimensional transition-metal dichalcogenides(2D TMDs). Herein, we report the direct identification of defectsof few layer 2H-TaSe2 on Au foils achieved by chemicalvapor deposition and their interactions with charge density wave (CDW)order via scanning tunneling microscopy (STM). Four types of defectsin 2H-TaSe2 are revealed by STM images and density functionaltheory (DFT) simulations, which are Se vacancy in the upper Se layer,Se vacancy in the bottom Se layer facing the substrate, Ta vacancy,and locally inserted 1T-TaSe2. Interestingly, the presenceof defects in 2H-TaSe2 layers can mediate the amplitudereduction or vanishing of the CDW order, and abundant defects caneven break up the long-range CDW phase into nanodomains. In addition,the amplitude of the CDW order is observed to increase gradually withincreasing sample bias voltage in STM imaging, possibly due to thedefect-induced electronic density inhomogeneity. Hereby, this workshould provide valuable insights for the effects of various defectstates on the CDW order in 2D metallic TMDs, thus propelling theirintriguing property investigations and the related device applications.