Tech Team · Kintek Solution

Gold coating for SEM (Scanning Electron Microscopy) is a critical step in sample preparation to ensure proper conductivity and prevent charging effects. The thickness of the gold coating typically ranges from 5 to 20 nanometers (nm), depending on the sample type, the resolution required, and the specific SEM instrument being used. A thinner coating (5-10 nm) is preferred for high-resolution imaging to minimize interference with fine surface details, while a thicker coating (10-20 nm) may be used for less conductive or rough samples to ensure adequate conductivity. The coating process is usually performed using a sputter coater, which deposits a uniform layer of gold onto the sample surface.

Key Points Explained:

1. Purpose of Gold Coating in SEM:

   • Gold coating is applied to non-conductive or poorly conductive samples to make them electrically conductive. This prevents charging effects, which can distort the SEM images.
   • It also enhances secondary electron emission, improving image quality and contrast.

2. Typical Thickness Range:

   • The gold coating thickness for SEM typically ranges from 5 to 20 nanometers (nm).
   • 5-10 nm: Used for high-resolution imaging where fine surface details need to be preserved.
   • 10-20 nm: Suitable for less conductive or rough samples to ensure sufficient conductivity.

3. Factors Influencing Coating Thickness:

   • Sample Conductivity: Non-conductive samples require thicker coatings to ensure conductivity.
   • Surface Roughness: Rough surfaces may need thicker coatings to cover irregularities.
   • Resolution Requirements: High-resolution imaging demands thinner coatings to avoid obscuring fine details.
   • SEM Instrument Specifications: Different SEM instruments may have specific requirements for coating thickness.

4. Coating Process:

   • Gold coating is typically applied using a sputter coater, which uses a plasma to deposit a thin, uniform layer of gold onto the sample surface.
   • The process is controlled to achieve the desired thickness, ensuring even coverage across the sample.

5. Advantages of Gold Coating:

   • Conductivity: Prevents charging effects and ensures stable imaging.
   • Enhanced Imaging: Improves secondary electron emission, leading to better image quality.
   • Durability: Gold is resistant to oxidation, making it suitable for long-term sample storage.

6. Alternatives to Gold Coating:

   • Other conductive materials like platinum, palladium, or carbon can be used depending on the application.
   • Carbon coating is often used for energy-dispersive X-ray spectroscopy (EDS) analysis, as it does not interfere with elemental detection.

7. Practical Considerations:

   • Over-coating can obscure fine details, while under-coating may lead to charging effects.
   • The optimal thickness should be determined experimentally based on the sample and imaging requirements.

By carefully controlling the gold coating thickness, SEM users can achieve high-quality images while preserving the integrity of the sample surface.

Summary Table:

Aspect	Details
Purpose	Ensures conductivity, prevents charging, and enhances image quality.
Thickness Range	5-20 nm (5-10 nm for high-res imaging, 10-20 nm for less conductive samples).
Factors to Consider	Sample conductivity, surface roughness, resolution, and SEM specifications.
Coating Process	Applied via sputter coater for uniform, controlled thickness.
Advantages	Prevents charging, improves imaging, and offers durability.
Alternatives	Platinum, palladium, or carbon coatings for specific applications.

Need help determining the right gold coating thickness for your SEM samples? Contact our experts today!