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Title: Growth of crystalline Al{sub 2}O{sub 3} via thermal atomic layer deposition: Nanomaterial phase stabilization

We report the growth of crystalline Al{sub 2}O{sub 3} thin films deposited by thermal Atomic Layer Deposition (ALD) at 200 °C, which up to now has always resulted in the amorphous phase. The 5 nm thick films were deposited on Ga{sub 2}O{sub 3}, ZnO, and Si nanowire substrates 100 nm or less in diameter. The crystalline nature of the Al{sub 2}O{sub 3} thin film coating was confirmed using Transmission Electron Microscopy (TEM), including high-resolution TEM lattice imaging, selected area diffraction, and energy filtered TEM. Al{sub 2}O{sub 3} coatings on nanowires with diameters of 10 nm or less formed a fully crystalline phase, while those with diameters in the 20–25 nm range resulted in a partially crystalline coating, and those with diameters in excess of 50 nm were fully amorphous. We suggest that the amorphous Al{sub 2}O{sub 3} phase becomes metastable with respect to a crystalline alumina polymorph, due to the nanometer size scale of the film/substrate combination. Since ALD Al{sub 2}O{sub 3} films are widely used as protective barriers, dielectric layers, as well as potential coatings in energy materials, these findings may have important implications.
Authors:
; ;  [1]
  1. Naval Research Laboratory, Washington, District of Columbia 20375 (United States)
Publication Date:
OSTI Identifier:
22269549
Resource Type:
Journal Article
Resource Relation:
Journal Name: APL Materials; Journal Volume: 2; Journal Issue: 3; Other Information: (c) 2014 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM OXIDES; AMORPHOUS STATE; DEPOSITS; DIELECTRIC MATERIALS; DIFFRACTION; GALLIUM OXIDES; QUANTUM WIRES; STABILIZATION; SUBSTRATES; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; ZINC OXIDES