Photonic Characterisation of Indium Tin Oxide as a Function of Deposition Conditions

TY - JOUR

T1 - Photonic Characterisation of Indium Tin Oxide as a Function of Deposition Conditions

AU - Blair, Samuel F.J.

AU - Male, Joshua S.

AU - Cavill, Stuart A.

AU - Reardon, Christopher P.

AU - Krauss, Thomas F.

N1 - Funding Information: We gratefully acknowledge funding by the EPSRC of the UK under grant number EP/V047663/1. Publisher Copyright: © 2023 by the authors.

PY - 2023/7/30

Y1 - 2023/7/30

N2 - Indium tin oxide (ITO) has recently gained prominence as a photonic nanomaterial, for example, in modulators, tuneable metasurfaces and for epsilon-near-zero (ENZ) photonics. The optical properties of ITO are typically described by the Drude model and are strongly dependent on the deposition conditions. In the current literature, studies often make several assumptions to connect the optically measured material parameters to the electrical properties of ITO, which are not always clear, nor do they necessarily apply. Here, we present a comprehensive study of the structural, electrical, and optical properties of ITO and showed how they relate to the deposition conditions. We use guided mode resonances to determine the dispersion curves of the deposited material and relate these to structural and electrical measurements to extract all relevant material parameters. We demonstrate how the carrier density, mobility, plasma frequency, electron effective mass, and collision frequency vary as a function of deposition conditions, and that the high-frequency permittivity ((Formula presented.)) can vary significantly from the value of (Formula presented.) = 3.9 that many papers simply assume to be a constant. The depth of analysis we demonstrate allows the findings to be easily extrapolated to the photonic characterisation of other transparent conducting oxides (TCOs), whilst providing a much-needed reference for the research area.

AB - Indium tin oxide (ITO) has recently gained prominence as a photonic nanomaterial, for example, in modulators, tuneable metasurfaces and for epsilon-near-zero (ENZ) photonics. The optical properties of ITO are typically described by the Drude model and are strongly dependent on the deposition conditions. In the current literature, studies often make several assumptions to connect the optically measured material parameters to the electrical properties of ITO, which are not always clear, nor do they necessarily apply. Here, we present a comprehensive study of the structural, electrical, and optical properties of ITO and showed how they relate to the deposition conditions. We use guided mode resonances to determine the dispersion curves of the deposited material and relate these to structural and electrical measurements to extract all relevant material parameters. We demonstrate how the carrier density, mobility, plasma frequency, electron effective mass, and collision frequency vary as a function of deposition conditions, and that the high-frequency permittivity ((Formula presented.)) can vary significantly from the value of (Formula presented.) = 3.9 that many papers simply assume to be a constant. The depth of analysis we demonstrate allows the findings to be easily extrapolated to the photonic characterisation of other transparent conducting oxides (TCOs), whilst providing a much-needed reference for the research area.

KW - Drude model

KW - epsilon-near-zero material

KW - guided mode resonance

KW - indium tin oxide

KW - nanomaterial

KW - transparent conducting oxides

UR - http://www.scopus.com/inward/record.url?scp=85164501229&partnerID=8YFLogxK

U2 - 10.3390/nano13131990

DO - 10.3390/nano13131990

M3 - Article

AN - SCOPUS:85164501229

SN - 2079-4991

VL - 13

JO - Nanomaterials

JF - Nanomaterials

IS - 13

M1 - 1990

ER -