On-Stack Two-Dimensional Conversion of MoS2 into MoO3

Abstract

Chemical transformation of existing two-dimensional (2D) materials can be crucial in further expanding the 2D crystal palette required to realize various functional heterostructures. In this work, we demonstrate a 2D 'on-stack' chemical conversion of single-layer crystalline MoS2 into MoO3 with a precise layer control that enables truly 2D MoO3 and MoO3/MoS2 heterostructures. To minimize perturbation of the 2D morphology, a nonthermal oxidation using O2 plasma was employed. The early stage of the reaction was characterized by a defect-induced Raman peak, drastic quenching of photoluminescence (PL) signals and sub-nm protrusions in atomic force microscopy images. As the reaction proceeded from the uppermost layer to the buried layers, PL and optical second harmonic generation signals showed characteristic modulations revealing a layer-by-layer conversion. The plasma-generated 2D oxides, confirmed as MoO3 by x-ray photoelectron spectroscopy, were found to be amorphous but extremely flat with a surface roughness of 0.18 nm, comparable to that of 1L MoS2. The rate of oxidation quantified by Raman spectroscopy decreased very rapidly for buried sulfide layers due to protection by the surface 2D oxides, exhibiting a pseudo-self-limiting behavior. As exemplified in this work, various on-stack chemical transformations can be applied to other 2D materials in forming otherwise unobtainable materials and complex heterostructures, thus expanding the palette of 2D material building blocks.

References in corpus (11)

• Electric Field Effect in Atomically Thin Carbon Films
• Two Dimensional Atomic Crystals
• Anomalous Lattice Vibrations of Single and Few-Layer MoS2
• Measurement of the Optical Conductivity of Graphene
• Atomic Structure of Graphene on SiO2
• Hunting for Monolayer Boron Nitride: Optical and Raman Signatures
• Optical Separation of Mechanical Strain from Charge Doping in Graphene
• Atomically thin boron nitride: a tunnelling barrier for graphene devices
• High-Resolution Scanning Tunneling Microscopy Imaging of Mesoscopic Graphene Sheets on an Insulating Surface
• Two-Dimensional Water Diffusion at a Graphene-Silica Interface
• Photoluminescence Quenching in Single-layer MoS2 via Oxygen Plasma Treatment

Cited by in corpus (7)

• Structural and optical properties of single- and few-layer magnetic semiconductor CrPS4
• Second-Harmonic Young Interference in Atom-Thin Heterocrystals
• Interface-Confined Doubly Anisotropic Oxidation of Two-Dimensional MoS2
• Photoresponsivity enhancement in monolayer MoS${}_2$ by rapid O${}_2$:Ar plasma treatment
• Exciton-Sensitized Second-Harmonic Generation in 2D Heterostructures
• Suppression of the Shear Raman Mode in Defective Bilayer MoS2
• Elucidating the role of electron transfer in the photoluminescence of $\mathrm{Mo}{\mathrm{S}}_2$ quantum dots synthesized by fs-pulse ablation