title: Ultrathin and Flat Layer Black Phosphorus Fabricated by Reactive Oxygen and Water Rinse.
abstract: Ultrathin black phosphorus (BP) is one of the promising two-dimensional (2D) materials for future optoelectronic devices. Its chemical instability in ambient conditions and lack of a bottom-up approach for its synthesis necessitate efficient etching methods that generate BP films of designed thickness with stable and high-quality surfaces. Herein, reporting a photochemical etching method, we demonstrate a controlled layer-by-layer thinning of thick BP films down to a few layers or a single layer and confirm their Raman and photoluminescence characteristics. Ozone molecules generated by O2 photolysis oxidize BP, forming P2O5-like oxides. When the resulting phosphorus oxides are removed by water, the surface of BP with preset thickness is highly flat and self-protective by surface oxygen functional groups. This method provides a fabrication strategy of BP and possibly other 2D semiconductors with band gaps tuned by their thickness.
authors: Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113, South Korea.
authors: Hyuksang
authors: H
authors: Kwon
authors: Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113, South Korea.|Korea University of Science and Technology (UST) , Daejeon 34113, South Korea.
authors: Sung Won
authors: SW
authors: Seo
authors: Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113, South Korea.|Korea University of Science and Technology (UST) , Daejeon 34113, South Korea.
authors: Tae Gun
authors: TG
authors: Kim
authors: Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113, South Korea.
authors: Eun Seong
authors: ES
authors: Lee
authors: Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113, South Korea.|Korea University of Science and Technology (UST) , Daejeon 34113, South Korea.
authors: Phung Thi
authors: PT
authors: Lanh
authors: Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113, South Korea.
authors: Sena
authors: S
authors: Yang
authors: Department of Chemistry & Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH) , Pohang, Gyeongbuk 37673, South Korea.
authors: Sunmin
authors: S
authors: Ryu
authors: Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113, South Korea.|Korea University of Science and Technology (UST) , Daejeon 34113, South Korea.
authors: Jeong Won
authors: JW
authors: Kim
keywords: etching; ozone; phosphorene (black phosphorus); protective layer; water