Ultrafast interfacial carrier dynamics and persistent topological surface states of Bi2Se3 in heterojunctions with VSe2
Tae Gwan Park, Jae Ho Jeon, Seung‐Hyun Chun, Sunghun Lee, Fabıan Rotermund
Abstract
Abstract Vanadium diselenide (VSe 2 ) has recently been highlighted as an efficient 2D electrode owing to its extra-high conductivity, thickness controllability, and van der Waals contact. However, as the electrode, applications of VSe 2 to various materials are still lacking. Here, by employing ultrafast time-resolved spectroscopy, we study VSe 2 -thickness-dependent interfacial effects in heterostructures with topological insulator Bi 2 Se 3 that is severely affected by contact with conventional 3D electrodes. Our results show unaltered Dirac surface state of Bi 2 Se 3 against forming junctions with VSe 2 , efficient ultrafast hot electron transfer from VSe 2 to Bi 2 Se 3 across the interface, shortened metastable carrier lifetimes in Bi 2 Se 3 due to dipole interactions enabling efficient current flow, and the electronic level shift (~tens meV) of bulk states of Bi 2 Se 3 by interfacial interactions, which is ~10 times lower compared to conventional electrodes, implying weak Fermi level pinning. Our observations confirm VSe 2 as an ideal electrode for efficient Bi 2 Se 3 -based-applications with full utilization of topological insulator characteristics.