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Impact of Composition x on the Refractive Index of Ni x O
Author(s) -
Becker Martin,
Michel Fabian,
Polity Angelika,
Klar Peter J.
Publication year - 2018
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201700463
Subject(s) - refractive index , analytical chemistry (journal) , x ray photoelectron spectroscopy , materials science , scanning electron microscope , thin film , substrate (aquarium) , chemical composition , crystallography , chemistry , nuclear magnetic resonance , nanotechnology , optoelectronics , physics , oceanography , organic chemistry , chromatography , geology , composite material
Epitaxial Ni x O thin films were grown on c ‐plane (0001) sapphire substrates by ion beam sputtering (IBS) of a Ni metal target in a mixed argon and oxygen atmosphere. The composition of the film was varied systematically by varying the O 2 :Ar ratio in the IBS process. Structural characterization was carried out by X‐ray diffraction and scanning electron microscopy. All the Ni x O samples grew (111)‐oriented out‐of‐plane and with a defined two‐fold in‐plane orientation relationship relative to the crystalline substrate. The surface morphologies of the samples were very similar. The chemical bonding information of the films was examined by X‐ray photoelectron spectroscopy showing that the composition x could be varied in a wide range of x ≈ 0.9 to 1.5. Optical characterization yielded a strong dependence of the spectral dispersion of the refractive index and the band gap of Ni x O on composition for this otherwise structurally very similar series of samples. The dependence of the refractive index of Ni x O on composition x contributes significantly to the wide range of values reported for Ni x O in literature.