Optical analysis of room temperature magnetron sputtered ITO films by reflectometry and spectroscopic ellipsometry

Abstract

Indium-tin-oxide (ITO) thin films were prepared by reactive magnetron sputtering, their optical constants and thickness were determined by spectral reflectometry (SR) in the wavelength range from 400 nm to 800 nm and spectroscopic ellipsometry (SE) in the wavelength range from 191 nm to 1690 nm. A comparative evaluation of the measured data from SR and SE has been made using the same single layer optical model based on the Cauchy dispersion relation. The introduction a surface roughness layer into the optical model considerably improved the fit quality during evaluation of SE data. Vertical inhomogeneity of the ITO thin films was assessed using a multilayer optical model describing porosity 1 gradient and the three-layer optical model suggested by Jung (Y.S. Jung, Thin Solid Films, 467, 36 (2004)) from the SE data.

Pulsed laser deposited indium tin oxides as alternatives to noble metals in the near-infrared region

“…However, the transparent window of the ITO film with P O2 = 5 Pa shrank to the range of 400-1300 nm; furthermore, the transmission window for the ITO film with P O2 = 1 Pa severely narrowed to 400-1000 nm. The gradual decrease of transmittance in the near-IR range and the narrowing of the transparent window were mainly due to the free carrier plasma resonance located in the near-IR range [47][48][49]. The free electrons oscillated with incident light with a specific frequency and screened the electromagnetic wave via intraband transitions within the conducting band [16,47].…”

“…Then an optical model was applied to retrieve the dielectric constant of the ITO film. Many works have been done to explore the optical property of ITO films using SE method by exclusively using the Drude and Lorentz model or Cauchy model to describe the optical constant of the ITO film in the visible range [34,[48][49][50]. Here the Drude model [35,51] was used to describe the metallic property of ITO films in the near-IR range (regardless of the interband absorption described by the Lorentz model in the UV range) and defined as follows:…”

Approximate methods for the optical characterization of inhomogeneous thin films: Applications to silicon nitride films

“…This reality is demonstrated by enormous number of scientific articles and many monographs dealing with optics of thin films. Enormous attention has been devoted to optics of homogeneous thin films in particular (see eg [1][2][3][4][5][6][7][8][9][10][11][12][13]). A less attention has been devoted to optics of inhomogeneous thin films since from the optical point of view these films are more complicated than homogeneous thin films.…”

Use of the Richardson extrapolation in optics of inhomogeneous layers: Application to optical characterization

“…Within the optical characterization and optical synthesis of thin films, inhomogeneous layers play an important role. While there are many works devoted to methods usable in optical characterization and optical synthesis of homogeneous thin films (see, eg, previous studies , less attention has been devoted to the methods enabling us to characterize or perform optical synthesis of inhomogeneous thin films exhibiting refractive index profiles. Therefore, it is necessary to develop new procedures usable in the optics of inhomogeneous layers.…”

“…In the literature, many procedures for calculating of the optical quantities of inhomogeneous layers have been published, eg, previous studies . The theoretical procedures can be divided into those providing the exact solution and those providing approximate solution.…”