ESCA (XPS)

 

Application:  

    • Measure the very top surface chemistry (1-12 nm)
      of any solid state or viscous material
    • Depth profile elemental or chemical states chemistry
      down to 1-2µ
    • Non-Destructively measure chemistry vs depth
      over the top 1-12 nm
    • Determine elemental composition of complete unknown
    • Reveal relative ratios or atoms of co-existing
      chemical states
    • By XY mapping determine the homogeneity/uniformity
      of any surface

 

Electron Spectroscopy for Chemical Analysis (ESCA), also known as X-ray photoelectron spectroscopy (XPS), is a quantitative spectroscopic technique that measures elemental composition, empirical formula, chemical state and electronic state of the elements that exist within a material. ESCA (XPS) spectra are obtained by irradiating a material with a beam of X-rays while simultaneously measuring the kinetic energy and number of electrons that escape from the top 1 to 12 nm of the material being analyzed. XPS requires ultra-high vacuum (UHV) conditions.

XPS is a surface chemical analysis technique that can be used to analyze the surface chemistry of a material in its’ “as received” state, or after some treatment, for example: fracturing, cutting or scraping in air or UHV to expose the bulk chemistry, ion beam etching to clean off some of the surface contamination, exposure to heat to study the changes due to heating, exposure to reactive gases or solutions, exposure to ion beam implant, exposure to ultraviolet light.

    • ESCA, an abbreviation for “electron spectroscopy for chemical analysis” was introduced by Kai Siegbahn and his research group. ESCA is also known as XPS
    • Detection limits for most of the elements are in the parts per thousand range (1,000 PPM). Detection limits of parts per million (ppm) are possible, but require special conditions: concentration at top surface or very long collection time.
    • XPS is routinely used to analyze inorganic compounds, metal alloys, semiconductors, polymers, elements, catalysts, glasses, ceramics,
      paints, papers, inks, woods, plant parts, make-up, teeth, bones, medical implants, bio-materials, viscous oils, glues, ion modified materials and many others.

XPS is used to measure:

    • elemental composition of the surface (top 1–12 nm usually)
    • empirical formula of pure materials
    • elements that contaminate a surface
    • chemical or electronic state of each element in the surface
    • uniformity of elemental composition across the top surface
      (or line profiling or mapping)
    • uniformity of elemental composition as a function of ion beam etching
      (or depth profiling)
 

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K-Alpha XPS system from Thermo Scientific



 

Survey Spectrum (to detect presence/absence of elements)



 

High-resolution spectrum for Si(2p) signal




 

Rough schematic of XPS physics  - “Photoelectric Effect





 

XPS vs EDS – Depth of Chemistry Information