Optical properties of bulk and thin-film SrTiO3 on Si and Pt

Stefan Zollner, A. A. Demkov, R. Liu, P. L. Fejes, R. B. Gregory, Prasad Alluri, J. A. Curless, Z. Yu, J. Ramdani, R. Droopad, T. E. Tiwald, J. N. Hilfiker, J. A. Woollam

Research output: Contribution to journalArticle

85 Citations (Scopus)

Abstract

We have studied the optical properties (complex dielectric function) of bulk SrTiO3 and thin films on Si and Pt using spectroscopic ellipsometry over a very broad spectral range, starting at 0.03 eV [using Fourier transform infrared (FTIR) ellipsometry] to 8.7 eV. In the bulk crystals, we analyze the interband transitions in the spectra to determine the critical-point parameters. To interpret these transitions, we performed band structure calculations based on ab initio pseudopotentials within the local-density approximation. The dielectric function was also calculated within this framework and compared with our ellipsometry data. In the FTIR ellipsometry data, we notice a strong lattice absorption peak due to oxygen-related vibrations. Two longitudinal optic (LO) phonons were also identified. In SrTiO3 films on Si, the refractive index below the band gap decreases with decreasing thickness because of the increasing influence of the amorphous interfacial layer between the SrTiO3 film and the Si substrate. There is also a decrease in amplitude and an increase in broadening of the critical points with decreasing thickness. In SrTiO3 films on Pt, there is a strong correlation between the crystallinity and texture of the films (mostly aligned with the Pt pseudosubstrate) and the magnitude of the refractive index, the Urbach tail below the bulk band edge, and the critical-point parameters. FTIR reflectance measurements of SrTiO3 on Pt (reflection-absorption spectroscopy) show absorption peaks at the LO phonon energies, a typical manifestation of the Berreman effect for thin insulating films on a metal. The Urbach tail in our ellipsomety data and the broadening of the optical phonons in SrTiO3 on Pt are most likely caused by oxygen vacancy clusters.

Original languageEnglish (US)
Pages (from-to)2242-2254
Number of pages13
JournalJournal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
Volume18
Issue number4
StatePublished - Dec 1 2000

Fingerprint

Optical properties
Ellipsometry
optical properties
Thin films
ellipsometry
thin films
Fourier transforms
critical point
Phonons
Infrared radiation
Optics
Refractive index
phonons
Local density approximation
optics
Spectroscopic ellipsometry
refractivity
Reflectometers
Oxygen vacancies
Electron transitions

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

Optical properties of bulk and thin-film SrTiO3 on Si and Pt. / Zollner, Stefan; Demkov, A. A.; Liu, R.; Fejes, P. L.; Gregory, R. B.; Alluri, Prasad; Curless, J. A.; Yu, Z.; Ramdani, J.; Droopad, R.; Tiwald, T. E.; Hilfiker, J. N.; Woollam, J. A.

In: Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, Vol. 18, No. 4, 01.12.2000, p. 2242-2254.

Research output: Contribution to journalArticle

Zollner, S, Demkov, AA, Liu, R, Fejes, PL, Gregory, RB, Alluri, P, Curless, JA, Yu, Z, Ramdani, J, Droopad, R, Tiwald, TE, Hilfiker, JN & Woollam, JA 2000, 'Optical properties of bulk and thin-film SrTiO3 on Si and Pt', Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, vol. 18, no. 4, pp. 2242-2254.
Zollner S, Demkov AA, Liu R, Fejes PL, Gregory RB, Alluri P et al. Optical properties of bulk and thin-film SrTiO3 on Si and Pt. Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures. 2000 Dec 1;18(4):2242-2254.
Zollner, Stefan ; Demkov, A. A. ; Liu, R. ; Fejes, P. L. ; Gregory, R. B. ; Alluri, Prasad ; Curless, J. A. ; Yu, Z. ; Ramdani, J. ; Droopad, R. ; Tiwald, T. E. ; Hilfiker, J. N. ; Woollam, J. A. / Optical properties of bulk and thin-film SrTiO3 on Si and Pt. In: Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures. 2000 ; Vol. 18, No. 4. pp. 2242-2254.
@article{28ed2d4127d64c9da9d58a4750476204,
title = "Optical properties of bulk and thin-film SrTiO3 on Si and Pt",
abstract = "We have studied the optical properties (complex dielectric function) of bulk SrTiO3 and thin films on Si and Pt using spectroscopic ellipsometry over a very broad spectral range, starting at 0.03 eV [using Fourier transform infrared (FTIR) ellipsometry] to 8.7 eV. In the bulk crystals, we analyze the interband transitions in the spectra to determine the critical-point parameters. To interpret these transitions, we performed band structure calculations based on ab initio pseudopotentials within the local-density approximation. The dielectric function was also calculated within this framework and compared with our ellipsometry data. In the FTIR ellipsometry data, we notice a strong lattice absorption peak due to oxygen-related vibrations. Two longitudinal optic (LO) phonons were also identified. In SrTiO3 films on Si, the refractive index below the band gap decreases with decreasing thickness because of the increasing influence of the amorphous interfacial layer between the SrTiO3 film and the Si substrate. There is also a decrease in amplitude and an increase in broadening of the critical points with decreasing thickness. In SrTiO3 films on Pt, there is a strong correlation between the crystallinity and texture of the films (mostly aligned with the Pt pseudosubstrate) and the magnitude of the refractive index, the Urbach tail below the bulk band edge, and the critical-point parameters. FTIR reflectance measurements of SrTiO3 on Pt (reflection-absorption spectroscopy) show absorption peaks at the LO phonon energies, a typical manifestation of the Berreman effect for thin insulating films on a metal. The Urbach tail in our ellipsomety data and the broadening of the optical phonons in SrTiO3 on Pt are most likely caused by oxygen vacancy clusters.",
author = "Stefan Zollner and Demkov, {A. A.} and R. Liu and Fejes, {P. L.} and Gregory, {R. B.} and Prasad Alluri and Curless, {J. A.} and Z. Yu and J. Ramdani and R. Droopad and Tiwald, {T. E.} and Hilfiker, {J. N.} and Woollam, {J. A.}",
year = "2000",
month = "12",
day = "1",
language = "English (US)",
volume = "18",
pages = "2242--2254",
journal = "Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures",
issn = "1071-1023",
publisher = "AVS Science and Technology Society",
number = "4",

}

TY - JOUR

T1 - Optical properties of bulk and thin-film SrTiO3 on Si and Pt

AU - Zollner, Stefan

AU - Demkov, A. A.

AU - Liu, R.

AU - Fejes, P. L.

AU - Gregory, R. B.

AU - Alluri, Prasad

AU - Curless, J. A.

AU - Yu, Z.

AU - Ramdani, J.

AU - Droopad, R.

AU - Tiwald, T. E.

AU - Hilfiker, J. N.

AU - Woollam, J. A.

PY - 2000/12/1

Y1 - 2000/12/1

N2 - We have studied the optical properties (complex dielectric function) of bulk SrTiO3 and thin films on Si and Pt using spectroscopic ellipsometry over a very broad spectral range, starting at 0.03 eV [using Fourier transform infrared (FTIR) ellipsometry] to 8.7 eV. In the bulk crystals, we analyze the interband transitions in the spectra to determine the critical-point parameters. To interpret these transitions, we performed band structure calculations based on ab initio pseudopotentials within the local-density approximation. The dielectric function was also calculated within this framework and compared with our ellipsometry data. In the FTIR ellipsometry data, we notice a strong lattice absorption peak due to oxygen-related vibrations. Two longitudinal optic (LO) phonons were also identified. In SrTiO3 films on Si, the refractive index below the band gap decreases with decreasing thickness because of the increasing influence of the amorphous interfacial layer between the SrTiO3 film and the Si substrate. There is also a decrease in amplitude and an increase in broadening of the critical points with decreasing thickness. In SrTiO3 films on Pt, there is a strong correlation between the crystallinity and texture of the films (mostly aligned with the Pt pseudosubstrate) and the magnitude of the refractive index, the Urbach tail below the bulk band edge, and the critical-point parameters. FTIR reflectance measurements of SrTiO3 on Pt (reflection-absorption spectroscopy) show absorption peaks at the LO phonon energies, a typical manifestation of the Berreman effect for thin insulating films on a metal. The Urbach tail in our ellipsomety data and the broadening of the optical phonons in SrTiO3 on Pt are most likely caused by oxygen vacancy clusters.

AB - We have studied the optical properties (complex dielectric function) of bulk SrTiO3 and thin films on Si and Pt using spectroscopic ellipsometry over a very broad spectral range, starting at 0.03 eV [using Fourier transform infrared (FTIR) ellipsometry] to 8.7 eV. In the bulk crystals, we analyze the interband transitions in the spectra to determine the critical-point parameters. To interpret these transitions, we performed band structure calculations based on ab initio pseudopotentials within the local-density approximation. The dielectric function was also calculated within this framework and compared with our ellipsometry data. In the FTIR ellipsometry data, we notice a strong lattice absorption peak due to oxygen-related vibrations. Two longitudinal optic (LO) phonons were also identified. In SrTiO3 films on Si, the refractive index below the band gap decreases with decreasing thickness because of the increasing influence of the amorphous interfacial layer between the SrTiO3 film and the Si substrate. There is also a decrease in amplitude and an increase in broadening of the critical points with decreasing thickness. In SrTiO3 films on Pt, there is a strong correlation between the crystallinity and texture of the films (mostly aligned with the Pt pseudosubstrate) and the magnitude of the refractive index, the Urbach tail below the bulk band edge, and the critical-point parameters. FTIR reflectance measurements of SrTiO3 on Pt (reflection-absorption spectroscopy) show absorption peaks at the LO phonon energies, a typical manifestation of the Berreman effect for thin insulating films on a metal. The Urbach tail in our ellipsomety data and the broadening of the optical phonons in SrTiO3 on Pt are most likely caused by oxygen vacancy clusters.

UR - http://www.scopus.com/inward/record.url?scp=23044524680&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=23044524680&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:23044524680

VL - 18

SP - 2242

EP - 2254

JO - Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures

JF - Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures

SN - 1071-1023

IS - 4

ER -