Thirty per cent contrast in secondary-electron imaging by scanning field-emission microscopy

Area of Science:

• Surface Science
• Materials Science
• Nanotechnology

Background:

• Scanning Tunnelling Microscopy (STM) is a primary tool for atomic-scale surface imaging.
• Field emission of electrons can be utilized for surface analysis beyond traditional STM.

Purpose of the Study:

• To explore and characterize the Scanning Field-Emission Microscopy (SFM) regime.
• To evaluate the contrast and resolution capabilities of SFM for surface step imaging.
• To investigate the underlying mechanisms for contrast generation in SFM.

Main Methods:

• Performing Scanning Tunnelling Microscopy (STM) experiments.
• Operating in a novel Scanning Field-Emission Microscopy (SFM) mode.
• Imaging monoatomic steps on W(110) surfaces with and without Fe coverage.

Main Results:

• SFM achieved a secondary-electron contrast as high as 30% for monoatomic steps.
• The observed contrast in SFM is comparable to that of STM.
• The apparent width of monoatomic steps in SFM was approximately 1 nm.
• SFM contrast originates from material-dependent secondary-electron yield, not tip-target distance.

Conclusions:

• SFM offers high-contrast imaging of surface topography, particularly at step edges.
• The technique provides complementary information to STM due to its reliance on secondary electron emission.
• Combining STM and SFM can enhance surface characterization and enable precise electron selection for further processing.