Suppression of Charge Density Wave by Substrate Induced Doping on TiSe${}_2$/TiO${}_2$ Heterostructure

Abstract

Substrate engineering provides an opportunity to modulate the physical properties of quantum materials in thin film form. Here we report that TiSe${}_2$ thin films grown on TiO${}_2$ have unexpectedly large electron doping that suppresses the charge density wave (CDW) order. This is dramatically different from either bulk single crystal TiSe${}_2$ or TiSe${}_2$ thin films on graphene. The epitaxial TiSe${}_2$ thin films can be prepared on TiO${}_2$ via molecular beam epitaxy (MBE) in two ways: by conventional co-deposition using selenium and titanium sources, and by evaporating only selenium on reconstructed TiO${}_2$ surfaces. Both growth methods yield atomically flat thin films with similar physical properties. The electron doping and subsequent suppression of CDW order can be explained by selenium vacancies in the TiSe${}_2$ film, which naturally occur when TiO${}_2$ substrates are used. This is due to the stronger interfacial bonding that changes the ideal growth conditions. Our finding provides a way to tune the chemical potential of chalcogenide thin films via substrate selection and engineering.

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