A proximal retarding field analyzer for scanning probe energy loss spectroscopy

Area of Science:

• Surface Science
• Nanotechnology
• Spectroscopy

Background:

• Scanning tunneling microscopy (STM) offers high-resolution surface topography but lacks elemental and electronic property mapping.
• Existing methods for combining STM with spectroscopy are often complex or lack simultaneous imaging capabilities.

Purpose of the Study:

• To describe a compact proximal retarding field analyzer for integration with STM.
• To demonstrate simultaneous electron reflectivity imaging and electron energy loss spectroscopy (EELS) using an STM tip as an electron source.

Main Methods:

• A compact retarding field analyzer was designed and positioned at a glancing angle to the sample surface.
• The scanning tunneling microscope (STM) tip was utilized as a field emission (FE) electron source.
• Simultaneous FE sample current, electron reflectivity imaging, and EELS measurements were performed.

Main Results:

• Demonstrated material contrast of 13% between silver nanostructures and graphite with 25 nm lateral resolution in electron reflectivity images.
• Observed topological contrast mechanisms including edge enhancement and shadowing.
• Successfully measured EELS spectra on graphite, identifying characteristic peaks.

Conclusions:

• The compact analyzer can easily augment STM systems for simultaneous elemental and topographic mapping.
• This approach supplements STM imaging with FE sample current, electron reflectivity, and EELS data within the same instrument.
• The developed system offers a versatile tool for advanced surface analysis.