AVS 61st International Symposium & Exhibition
    Thin Film Friday Sessions
       Session TF+AS-FrM

Paper TF+AS-FrM4
The Equivalent Width as a Figure of Merit for XPS Narrow Scans

Friday, November 14, 2014, 9:20 am, Room 307

Session: Thin Film Characterization
Presenter: Matthew Linford, Brigham Young University
Authors: M.R. Linford, Brigham Young University
B. Singh, Brigham Young University
J. Terry, Illinois Institute of Technology
Correspondent: Click to Email
X-ray Photoelectron Spectroscopy (XPS) is a widely used surface analytical tool that provides information about the near surface regions of materials. In particular, chemical state information is often obtained from peak fitting XPS narrow scans. And while indispensable for XPS data analysis, peak fitting can be a fairly subjective exercise. Herein we introduce the use of the equivalent width (EW) as an additional and less subjective figure of merit for XPS narrow scans. The EWXPS is simply defined as the area of a narrow scan divided by the height of the maximum of its peak envelope. To limit any ambiguity in EWXPS for a series of spectra, we may also list the peak position of the maximum of the envelope (PEmax). We provide and discuss four examples that demonstrate the use of these parameters including (i) four C 1s narrow scans of ozone-treated carbon nanotubes (EWXPS ~ 2.11 – 2.16 eV for a Shirley background, and up to 2.88 eV for no background, PEmax ~ 284.4 – 284.5 eV), (ii) a series of silicon wafers with different oxide thicknesses (EWXPS ~ 1.5 – 2.8 eV, PEmax ~ 99 – 103 eV), (iii) hydrogen-terminated silicon before and after derivatization with pentyl groups, and after annealing of the pentyl-modified material (EWXPS ~ 0.7 – 1.0 eV, PEmax ~ 25.9 – 26.1 eV), and (iv) five C 1s narrow scans of nanodiamond samples, where three of the spectra showed charging (EWXPS ~ 2.6 – 4.9 eV, PEmax ~ 272.7 – 293.9 eV). In this final example, EWXPS was plotted against PEmax to identify the region corresponding to the materials that showed the least charging. EWXPS and PEmax appear to correlate with the expected chemistries of all the systems studied. We calculate EWXPS using a Shirley baseline and with no baseline at all. In setting the baseline limits for EWXPS, we consider the derivative of C 1s narrow scans. We also show the application of EWXPS to single, fitted components within a narrow scan. Other width functions are also discussed.