Multiple oscillator models for the optical constants of polycrystalline zinc oxide thin films over a wide wavelength range

J. M. Khoshman, J. N. Hilfiker, Nouar Tabet, M. E. Kordesch

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Zinc oxide (ZnO) films were prepared on Si(1 1 1) and quartz substrates using RF-magnetron sputtering in N2 plasma at room temperature. From the X-ray diffraction observations, it was found that all films are polycrystalline with a preferred orientation of (1 0 1). X ray photoelectron spectroscopy was used to analyze the chemical composition of the films by observing the behavior of the Zn2p3, O1s, N1s, and C1s lines. The thicknesses and optical constants of the ZnO thin films were determined using variable angle spectroscopic ellipsometry through the Genosc™ Herzinger-Johs parameterized semiconductor oscillator functions and multiple Gaussian oscillator models. Combining multiple oscillator types provided a very flexible approach to fitting optical constants over a wavelength range 190-1400 nm while simultaneously enforcing Kramers-Kronig consistency in the fitted ellipsometric parameters. Refractive indices of the films were determined to be in the range 1.68-1.93 and extinction coefficients in the range 4.56 × 10 -6-0.23. A direct bandgap of 3.38 ± 0.03 eV was calculated from the extinction coefficient. Low temperature photoluminescence studies of the films exhibited one prominent peak at 3.41 eV. The equality of the ZnO thin films was obtained through the depolarization measurements.

Original languageEnglish
Pages (from-to)558-565
Number of pages8
JournalApplied Surface Science
Volume307
DOIs
Publication statusPublished - 15 Jul 2014
Externally publishedYes

Fingerprint

Zinc Oxide
Optical constants
Zinc oxide
Oxide films
Thin films
Wavelength
Quartz
Spectroscopic ellipsometry
Depolarization
Magnetron sputtering
Refractive index
Photoluminescence
Energy gap
X ray photoelectron spectroscopy
Semiconductor materials
Plasmas
X ray diffraction
Temperature
Substrates
Chemical analysis

Keywords

  • Bandgap energy
  • Depolarization
  • Ellipsometric parameters
  • Gaussian oscillator
  • Optical constants
  • ZnO

ASJC Scopus subject areas

  • Surfaces, Coatings and Films

Cite this

Multiple oscillator models for the optical constants of polycrystalline zinc oxide thin films over a wide wavelength range. / Khoshman, J. M.; Hilfiker, J. N.; Tabet, Nouar; Kordesch, M. E.

In: Applied Surface Science, Vol. 307, 15.07.2014, p. 558-565.

Research output: Contribution to journalArticle

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