title: Al2O3 on Black Phosphorus by Atomic Layer Deposition: An in Situ Interface Study.
abstract: In situ "half cycle" atomic layer deposition (ALD) of Al2O3 was carried out on black phosphorus ("black-P") surfaces with modified phosphorus oxide concentrations. X-ray photoelectron spectroscopy is employed to investigate the interfacial chemistry and the nucleation of the Al2O3 on black-P surfaces. This work suggests that exposing a sample that is initially free of phosphorus oxide to the ALD precursors does not result in detectable oxidation. However, when the phosphorus oxide is formed on the surface prior to deposition, the black-P can react with both the surface adventitious oxygen contamination and the H2O precursor at a deposition temperature of 200 °C. As a result, the concentration of the phosphorus oxide increases after both annealing and the atomic layer deposition process. The nucleation rate of Al2O3 on black-P is correlated with the amount of oxygen on samples prior to the deposition. The growth of Al2O3 follows a "substrate inhibited growth" behavior where an incubation period is required. Ex situ atomic force microscopy is also used to investigate the deposited Al2O3 morphologies on black-P where the Al2O3 tends to form islands on the exfoliated black-P samples. Therefore, surface functionalization may be needed to get a conformal coverage of Al2O3 on the phosphorus oxide free samples.
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhu
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Stephen
authors.initials: S
authors.lastname: McDonnell
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Xiaoye
authors.initials: X
authors.lastname: Qin
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Angelica
authors.initials: A
authors.lastname: Azcatl
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Lanxia
authors.initials: L
authors.lastname: Cheng
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Rafik
authors.initials: R
authors.lastname: Addou
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Kim
authors.affiliation: ‡School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States.
authors.forename: Peide D
authors.initials: PD
authors.lastname: Ye
authors.affiliation: †Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Wallace
keywords: X-ray photoelectron spectroscopy; aluminum oxide; atomic layer deposition; black phosphorus; surface oxidation; water