View in EDS

Metrology of ultrathin iron catalyst films by spectroscopic ellipsometry.

Saved in:
Bibliographic Details
Title: Metrology of ultrathin iron catalyst films by spectroscopic ellipsometry.
Authors: Allen, Nicholas E.1 (AUTHOR), Linford, Matthew R.2 (AUTHOR), Allred, David D.1 (AUTHOR), Vanfleet, Richard R.1 (AUTHOR), Davis, Robert C.1 (AUTHOR)
Source: Journal of Vacuum Science & Technology: Part A-Vacuums, Surfaces & Films. Jul2026, Vol. 44 Issue 4, p1-11. 11p.
Subjects: Iron catalysts, Ellipsometry, Iron oxidation, Thin films, Nanotubes, Optical constants
Abstract: Vertically aligned carbon nanotube forest growth uses a thin-film iron catalyst on an alumina support. The iron catalyst thickness (typically, 1–10 nm) strongly affects forest morphology. We explored the use of spectroscopic ellipsometry (SE) as a rapid, sensitive, and nondestructive metrology method for these films. SE does have challenges, however, as it is difficult to break the correlation in the analysis between fitted optical constants and thickness of ultrathin films. Partial oxidation and optical absorption in the iron–iron oxide films add further complexity. We performed a multisample SE analysis of thermally evaporated iron films with target thicknesses of 1–14 nm. To improve sensitivity, we used interference enhancement by incorporating a 350 nm silica film on a silicon substrate beneath the iron film and alumina support. We used a consecutive-layer approach, collecting SE data and fitting the optical constants and thickness of each film before depositing the next. The iron–iron oxide film was modeled with an effective medium approximation layer. The model fit the data well with a mean squared error of 25. From the SE results, we estimated the thickness of the iron film before oxidation ("equivalent iron thickness"). We found that SE is highly sensitive to equivalent iron thickness and yields repeatable thickness measurements (ca. ±0.015 nm). We determined that the equivalent iron thickness variation we observed across different measurement locations on the same sample can be explained by error propagation from uncertainty in the underlying alumina thickness. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Vacuum Science & Technology: Part A-Vacuums, Surfaces & Films is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
FullText Text:
  Availability: 0
Header DbId: egs
DbLabel: Engineering Source
An: 195070452
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 0
IllustrationInfo
Items – Name: Title
  Label: Title
  Group: Ti
  Data: Metrology of ultrathin iron catalyst films by spectroscopic ellipsometry.
– Name: Author
  Label: Authors
  Group: Au
  Data: <searchLink fieldCode="AR" term="%22Allen%2C+Nicholas+E%2E%22">Allen, Nicholas E.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Linford%2C+Matthew+R%2E%22">Linford, Matthew R.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Allred%2C+David+D%2E%22">Allred, David D.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Vanfleet%2C+Richard+R%2E%22">Vanfleet, Richard R.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Davis%2C+Robert+C%2E%22">Davis, Robert C.</searchLink><relatesTo>1</relatesTo> (AUTHOR)
– Name: TitleSource
  Label: Source
  Group: Src
  Data: <searchLink fieldCode="JN" term="%22Journal+of+Vacuum+Science+%26+Technology%3A+Part+A-Vacuums%2C+Surfaces+%26+Films%22">Journal of Vacuum Science & Technology: Part A-Vacuums, Surfaces & Films</searchLink>. Jul2026, Vol. 44 Issue 4, p1-11. 11p.
– Name: Subject
  Label: Subjects
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Iron+catalysts%22">Iron catalysts</searchLink><br /><searchLink fieldCode="DE" term="%22Ellipsometry%22">Ellipsometry</searchLink><br /><searchLink fieldCode="DE" term="%22Iron+oxidation%22">Iron oxidation</searchLink><br /><searchLink fieldCode="DE" term="%22Thin+films%22">Thin films</searchLink><br /><searchLink fieldCode="DE" term="%22Nanotubes%22">Nanotubes</searchLink><br /><searchLink fieldCode="DE" term="%22Optical+constants%22">Optical constants</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Vertically aligned carbon nanotube forest growth uses a thin-film iron catalyst on an alumina support. The iron catalyst thickness (typically, 1–10 nm) strongly affects forest morphology. We explored the use of spectroscopic ellipsometry (SE) as a rapid, sensitive, and nondestructive metrology method for these films. SE does have challenges, however, as it is difficult to break the correlation in the analysis between fitted optical constants and thickness of ultrathin films. Partial oxidation and optical absorption in the iron–iron oxide films add further complexity. We performed a multisample SE analysis of thermally evaporated iron films with target thicknesses of 1–14 nm. To improve sensitivity, we used interference enhancement by incorporating a 350 nm silica film on a silicon substrate beneath the iron film and alumina support. We used a consecutive-layer approach, collecting SE data and fitting the optical constants and thickness of each film before depositing the next. The iron–iron oxide film was modeled with an effective medium approximation layer. The model fit the data well with a mean squared error of 25. From the SE results, we estimated the thickness of the iron film before oxidation ("equivalent iron thickness"). We found that SE is highly sensitive to equivalent iron thickness and yields repeatable thickness measurements (ca. ±0.015 nm). We determined that the equivalent iron thickness variation we observed across different measurement locations on the same sample can be explained by error propagation from uncertainty in the underlying alumina thickness. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Vacuum Science & Technology: Part A-Vacuums, Surfaces & Films is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=egs&AN=195070452
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1116/6.0005371
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 11
        StartPage: 1
    Subjects:
      – SubjectFull: Iron catalysts
        Type: general
      – SubjectFull: Ellipsometry
        Type: general
      – SubjectFull: Iron oxidation
        Type: general
      – SubjectFull: Thin films
        Type: general
      – SubjectFull: Nanotubes
        Type: general
      – SubjectFull: Optical constants
        Type: general
    Titles:
      – TitleFull: Metrology of ultrathin iron catalyst films by spectroscopic ellipsometry.
        Type: main
  BibRelationships:
    HasContributorRelationships:
      – PersonEntity:
          Name:
            NameFull: Allen, Nicholas E.
      – PersonEntity:
          Name:
            NameFull: Linford, Matthew R.
      – PersonEntity:
          Name:
            NameFull: Allred, David D.
      – PersonEntity:
          Name:
            NameFull: Vanfleet, Richard R.
      – PersonEntity:
          Name:
            NameFull: Davis, Robert C.
    IsPartOfRelationships:
      – BibEntity:
          Dates:
            – D: 01
              M: 07
              Text: Jul2026
              Type: published
              Y: 2026
          Identifiers:
            – Type: issn-print
              Value: 07342101
          Numbering:
            – Type: volume
              Value: 44
            – Type: issue
              Value: 4
          Titles:
            – TitleFull: Journal of Vacuum Science & Technology: Part A-Vacuums, Surfaces & Films
              Type: main
ResultId 1