Modulation of electrical properties in MoTe2 by XeF2-mediated surface oxidation

Abstract

Transition metal dichalcogenides (TMDs) are promising candidates for the semiconductor industry owing to their superior electrical properties. Their surface oxidation is of interest because their electrical properties can be easily modulated by an oxidized layer on top of them. Here, we demonstrate the XeF₂-mediated surface oxidation of 2H-MoTe₂ (alpha phase MoTe₂). MoTe₂ exposed to XeF₂ gas forms a thin and uniform oxidized layer (∼2.5 nm-thick MoO_x) on MoTe₂ regardless of the exposure time (within ∼120 s) due to the passivation effect and simultaneous etching. We used the oxidized layer for contacts between the metal and MoTe₂, which help reduce the contact resistance by overcoming the Fermi level pinning effect by the direct metal deposition process. The MoTe₂ field-effect transistors (FETs) with a MoO_x interlayer exhibited two orders of magnitude higher field-effect hole mobility of 6.31 cm² V⁻¹ s⁻¹ with a high on/off current ratio of ∼10⁵ than that of the MoTe₂ device with conventional metal contacts (0.07 cm² V⁻¹ s⁻¹). Our work shows a straightforward and effective method for forming a thin oxide layer for MoTe₂ devices, applicable for 2D electronics.