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

TL;DR

This study demonstrates that TiSe₂ thin films grown on TiO₂ substrates experience significant electron doping due to selenium vacancies, which suppresses charge density wave order, highlighting substrate engineering as a tool to tune electronic properties.

Contribution

It reveals substrate-induced doping effects in TiSe₂ films and links selenium vacancies to the suppression of charge density wave order, offering new avenues for material property control.

Findings

TiSe₂ films on TiO₂ show large electron doping.

Electron doping suppresses charge density wave order.

Selenium vacancies caused by substrate bonding explain doping.

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.