title: Self-limiting layer-by-layer oxidation of atomically thin WSe2.
abstract: Growth of a uniform oxide film with a tunable thickness on two-dimensional transition metal dichalcogenides is of great importance for electronic and optoelectronic applications. Here we demonstrate homogeneous surface oxidation of atomically thin WSe2 with a self-limiting thickness from single- to trilayers. Exposure to ozone (O3) below 100 °C leads to the lateral growth of tungsten oxide selectively along selenium zigzag-edge orientations on WSe2. With further O3 exposure, the oxide regions coalesce and oxidation terminates leaving a uniform thickness oxide film on top of unoxidized WSe2. At higher temperatures, oxidation evolves in the layer-by-layer regime up to trilayers. The oxide films formed on WSe2 are nearly atomically flat. Using photoluminescence and Raman spectroscopy, we find that the underlying single-layer WSe2 is decoupled from the top oxide but hole-doped. Our findings offer a new strategy for creating atomically thin heterostructures of semiconductors and insulating oxides with potential for applications in electronic devices.
authors: WPI Center for Materials Nanoarchitechtonics (WPI-MANA) and ‡International Center for Young Scientists, National Institute for Materials Science , Tsukuba, Ibaraki 305-0044, Japan.
authors: Mahito
authors: M
authors: Yamamoto
authors: Sudipta
authors: S
authors: Dutta
authors: Shinya
authors: S
authors: Aikawa
authors: Shu
authors: S
authors: Nakaharai
authors: Katsunori
authors: K
authors: Wakabayashi
authors: Michael S
authors: MS
authors: Fuhrer
authors: Keiji
authors: K
authors: Ueno
authors: Kazuhito
authors: K
authors: Tsukagoshi
keywords: Layered transition metal dichalcogenides; Raman spectroscopy; X-ray photoelectron spectroscopy; ab initio calculations; oxidation; photoluminescence; tungsten diselenide