Reflection Electron Energy Loss Spectroscopy (REELS)

Analysis Examples

Band gap measurement by REELS

*This is a REELS spectrum of a thermally oxidized SiO₂ film (25 nm) on a Si wafer. A peak onset is observed at an energy 8.8 eV lower than the incident electrons, from which the band gap of the SiO₂ film ⁽¹⁾ can be determined.

Fig 1. REELS spectrum of SiO₂ (incident electron energy: 1.5 keV)

Evaluation of hydrogen content in organic films by REELS

Due to the recoil effect of hydrogen atoms, an energy loss peak derived from hydrogen appears. The relative hydrogen content can be compared from the intensity of this peak.

Fig 2. REELS spectra of various polymer films (incident electron energy: 1.5 keV, 100 pA)

Evaluation of diamond-like carbon (DLC) films by REELS

*Using diamond (sp³) and graphite (sp²) as references, the bonding states of various DLC films can be identified ⁽²⁾. By removing surface contamination without damage using a gas cluster ion beam (GCIB), carbon materials can be analyzed with greater precision.

Fig 3. REELS spectra of graphite (sp²), diamond (sp³), DLC film deposited by Filtered Arc Deposition (FAD) method, and DLC film on the inner surface of a PET bottle (high-barrier PET bottle) (incident electron energy: 1 keV)

Principles of REELS

The energy loss spectrum of reflected electrons generated by irradiating a sample with electrons reflects the energy and frequency of excitations occurring at the surface. From the energy loss spectrum of reflected electrons, the electronic state of the surface, such as the bonding state of atoms and the band gap, can be analyzed.

Configuration of REELS

REELS measurement is made possible by selecting one of two types of electron guns as an option for the VersaProbe III. Both electron guns enable REELS measurement with high energy resolution of 0.5 eV or below in FAT mode (constant energy resolution).

Electron gun for REELS

This is a newly developed cost-effective electron gun for REELS measurement.
It can irradiate stable electrons from a few hundred volts up to a maximum of 2 kV.

Scanning electron gun for Auger analysis

When the Auger option is selected, REELS measurement is possible using the scanning electron gun for Auger analysis.
REELS analysis can be performed by specifying the measurement location on the SEM image.
（For details, please contact our domestic sales department.）

References

T.H. DiStefano, D.E. Eastman, Solid State Communications, Volume 9, Issue 24, pp. 2259-2261 (1971)
横溝臣智, Journal of Surface Analysis 20, pp. 18-24 (2013)

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