title: Oxidation Effect in Octahedral Hafnium Disulfide Thin Film.
abstract: Atomically smooth van der Waals materials are structurally stable in a monolayer and a few layers but are susceptible to oxygen-rich environments. In particular, recently emerging materials such as black phosphorus and perovskite have revealed stronger environmental sensitivity than other two-dimensional layered materials, often obscuring the interesting intrinsic electronic and optical properties. Unleashing the true potential of these materials requires oxidation-free sample preparation that protects thin flakes from air exposure. Here, we fabricated few-layer hafnium disulfide (HfS2) field effect transistors (FETs) using an integrated vacuum cluster system and study their electronic properties and stability under ambient conditions. By performing all the device fabrication and characterization procedure under an oxygen- and moisture-free environment, we found that few-layer AA-stacking HfS2-FETs display excellent field effect responses (Ion/Ioff ≈ 10(7)) with reduced hysteresis compared to the FETs prepared under ambient conditions. Oxidation of HfS2 occurs uniformly over the entire area, increasing the film thickness by 250% at a prolonged oxidation time of >120 h, while defects on the surface are the preferential initial oxidation sites. We further demonstrated that the stability of the device in air is significantly improved by passivating FETs with BN in a vacuum cluster.
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Chae
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Youngjo
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Tae Soo
authors.initials: TS
authors.lastname: Kim
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Dong Seob
authors.initials: DS
authors.lastname: Chung
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Hyunyeong
authors.initials: H
authors.lastname: Na
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Honggi
authors.initials: H
authors.lastname: Nam
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Kim
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: David J
authors.initials: DJ
authors.lastname: Perello
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Hye Yun
authors.initials: HY
authors.lastname: Jeong
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Thuc Hue
authors.initials: TH
authors.lastname: Ly
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), ‡Department of Energy Science, and §Department of Physics, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Young Hee
authors.initials: YH
authors.lastname: Lee
keywords: boron nitride; field effect transistor; glovebox; hafnium disulfide; oxidation; vacuum cluster