Degenerate electron-doping in two-dimensional tungsten diselenide with a dimeric organometallic reductant

Abstract: The large Schottky barriers formed at metal–semiconductor junctions severely limit the development of transition metal dichalcogenide (TMDC)-based ultrathin electronics and optoelectronics. Various approaches to create Ohmic contacts at TMDC and metal interface have been developed, including contact phase engineering, contact doping, buffer layer engineering, and contact integration engineering. Here, we report degenerate electron doping of mono- and bi-layer tungsten diselenide (WSe₂) by a molecular organometallic donor, [RuCp*(mes)]₂. In-situ evaporation of [RuCp*(mes)]₂ molecules onto WSe₂ field-effect transistors in vacuum leads to a remarkably diminished gate dependence of the transport property and a large enhancement of electrical conductance by five orders of magnitude, implying the great potential of this doping approach in tuning the Schottky barrier for TMDC devices. The interfacial electronic structure at the WSe₂–dopant interface was revealed through the combination of in-situ photoelectron spectroscopy investigations and theoretical calculations. Moreover, the doped device is found to be robust in oxygen and nitrogen atmosphere and also moderately stable in humid air, which is favorable in device applications.

https://doi.org/10.1016/j.mattod.2019.04.017