2D Materials / Alfa Chemistry
X-Ray Photoelectron Spectroscopy for 2D Materials
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X-Ray Photoelectron Spectroscopy for 2D Materials

There has been an explosion in the research of two-dimensional (2D) materials since the discoveries and isolation of graphene. Changes in either of the two key factors of 2D materials, chemical composition and layer count, can have a significant impact on the material's viability. This necessitates the ability to precisely quantify materials.

X-ray photoelectron spectroscopy (XPS) can be used to identify and locate any specific compounds or components that are present on a surface. Alfa Chemistry provides XPS testing to characterize the elemental and chemical composition of 2D material surfaces, which is critical for understanding 2D material properties. Please contact us right away so that we can help you with your tests!


XPS technology is based on the photoelectric effect. Photoelectrons are released from the atoms near the surface when a material is bombarded with X-rays. The kinetic energy of the emitted photoelectrons is equal to the difference between the photon energy and the electron binding energy. The approach is inherently surface-sensitive because of the low energy of the X-rays. The sample's outer 1-10 nm contains the majority of the measured signal. The spectrum comprises information on the surface and near-surface atoms' elemental makeup, concentration, and chemical environment (i.e. oxidation state). Larger depths (up to a few microns) can be investigated by combining this technique with ion milling.

Nondestructive depth profile reconstruction of single-layer graphene using angle-resolved X-ray photoelectron spectroscopy.Fig 1. Nondestructive depth profile reconstruction of single-layer graphene using angle-resolved X-ray photoelectron spectroscopy. (Zemek J, et al. 2019)

XPS has been used to characterize the thickness and chemical composition of a variety of 2D films. Evaluating materials with XPS requires a calibration combination of performance for reliable comparison, reliable measurement of chemical shifts and identification of elements, and an understanding of measurement uncertainties.

The technology enables rapid and accurate evaluation of 2D materials, as well as the manipulation of growth conditions to efficiently manufacture extremely thin 2D materials over large areas. In addition, XPS measurements of typical 2D materials are non-destructive and do not require special sample preparation. Therefore, after XPS analysis, the exact same sample can be further processed or utilized.

Service Detail

Testing ServicesX-ray Photoelectron Spectroscopy (XPS)
Test ContentFull and narrow spectrum testing, Auger spectroscopy, Valence band spectroscopy, Depth profile analysis, Mapping, Angular resolution
Sample TypePowder / Film / Bulk
Instrument ModelThermo K-Alpha XPS, AXIS Supra+: XPS Surface Analysis Instrument
Lead Time2~3 Weeks

Our requirements for samples are as follows:

  • For powder sample

Please provide 20 ~ 30 mg sample. Customers need to use centrifuge tubes to load their samples. If the quantity is limited, please contact us.

  • For bulk/film samples

Please provide samples within 5 × 5 × 3 mm in size. For larger sample sizes, please contact us for a quote.

  • Special needs

Please contact us in advance if you have any special requirements for the following, additional charges may apply:
(1) Etching over 5 nm
(2) Samples containing S, F elements
(3) Any other special preparation (scan time, etc)

Sample requirements


  • Please try to vacuum seal the sample after preparation; otherwise, airborne pollutants may absorb the sample and impact the results for some elements.
  • We may not be able to identify the signal for elements below 5wt%.
  • For narrow-spectrum testing, Alfa Chemistry defaults to the strongest peak. If the strongest peak overlaps with another element, we will take the second strongest peak.
  • All samples are non-refundable; if you have any specific demands, please contact us.


  1. Zemek J, et al. (2019). "Non-Destructive Depth Profile Reconstruction of Single-Layer Graphene Using Angle-Resolved X-Ray Photoelectron Spectroscopy" Applied Surface Science. 491: 16-23.

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