Open AccessEffect of oxygen stoichiometry on the structure, optical and epsilon-near-zero properties of indium tin oxide films
Author(s) -
Shilin Xian,
Lixia Nie,
Jun Qin,
Tongtong Kang,
Chaoyang Li,
Jianliang Xie,
Longjiang Deng,
Lei Bi
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.028618
Subject(s) - indium tin oxide , materials science , drude model , stoichiometry , thin film , transparent conducting film , ellipsometry , optoelectronics , oxide , optics , analytical chemistry (journal) , indium , nanotechnology , chemistry , physics , organic chemistry , chromatography , metallurgy
Transparent conductive oxide (TCO) films showing epsilon near zero (ENZ) properties have attracted great research interest due to their unique property of electrically tunable permittivity. In this work, we report the effect of oxygen stoichiometry on the structure, optical and ENZ properties of indium tin oxide (ITO) films fabricated under different oxygen partial pressures. By using spectroscopic ellipsometry (SE) with fast data acquisition capabilities, we observed modulation of the material index and ENZ wavelength under electrostatic gating. Using a two-layer model based on Thomas-Fermi screening model and the Drude model, the optical constants and Drude parameters of the ITO thin films are determined during the gating process. The maximum carrier modulation amplitude ΔN of the accumulation layer is found to vary significantly depending on the oxygen stoichiometry. Under an electric field gate bias of 2.5 MV/cm, the largest ENZ wavelength modulation up to 27.9 nm at around 1550 nm is observed in ITO thin films deposited with oxygen partial pressure of P O 2 =10 Pa. Our work provides insights to the optical properties of ITO during electrostatic gating process for electro-optic modulators (EOMs) applications.