Metallic deposition in specimens presenting cavities using the sputter coater

Area of Science:

• Materials Science
• Microscopy
• Biological Imaging

Background:

• Scanning electron microscopy (SEM) is crucial for biological imaging.
• Sputter coating is used to mitigate charging artifacts in SEM.
• Small biological cavities present unique challenges for SEM observation due to charging effects.

Purpose of the Study:

• To investigate the extent of local charging effects in small biological cavities during SEM.
• To quantify the metallic coating thickness at the bottom of cylindrical cavities after sputter coating.
• To determine the relationship between cavity dimensions and coating thickness.

Main Methods:

• An experimental model simulating biological cavities was employed.
• Cylindrical cavities of varying diameter-to-depth ratios were created.
• Metallic coating thickness was measured at the bottom and surface of the cavities.

Main Results:

• Local charging effects were observed in biological cavities, persisting after sputter coating.
• The metallic coating thickness at the bottom of cylindrical cavities was found to be less than 50% of the surface coating thickness.
• Coating thickness was dependent on the diameter-to-depth ratio of the cylindrical cavities.

Conclusions:

• Sputter coating alone is insufficient to eliminate charging artifacts in small biological cavities.
• Cavity geometry significantly influences the effectiveness of sputter coating.
• Understanding these charging effects is critical for accurate SEM interpretation of biological samples.