Trace elemental analysis at nanometer spatial resolution by parallel-detection electron energy loss spectroscopy

Area of Science:

• Materials Science
• Analytical Chemistry
• Physics

Background:

• Elemental microanalysis is crucial for understanding material composition at the nanoscale.
• Traditional electron energy loss spectroscopy (EELS) methods face limitations in sensitivity and are affected by detector noise.
• Scanning transmission electron microscopy (STEM) offers high spatial resolution but requires sensitive analytical techniques.

Purpose of the Study:

• To develop a highly sensitive EELS technique for elemental microanalysis.
• To overcome limitations of detector pattern noise in EELS.
• To achieve trace element detection at the atomic ppm level with high spatial resolution.

Main Methods:

• Utilizing parallel-detection electron energy loss spectroscopy (EELS) integrated with scanning transmission electron microscopy (STEM).
• Employing a field emission source for enhanced signal generation.
• Implementing a difference spectrum method to minimize detector pattern noise by subtracting sequentially collected energy-shifted spectra.

Main Results:

• Achieved unprecedented sensitivity for elemental microanalysis, detecting signals less than 0.1% of the background.
• Demonstrated trace sensitivity at the 10 atomic ppm level for various elements (alkaline earths, 3-d transition metals, lanthanides).
• Attained near-single atom detectability for analytical volumes of approximately 10 nm.

Conclusions:

• The developed parallel-detection EELS-STEM technique significantly enhances elemental microanalysis sensitivity.
• This method enables highly accurate trace element quantification and mapping at the nanoscale.
• The technique opens new possibilities for analyzing materials with extremely low elemental concentrations.