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Backscattered electron imaging for high resolution surface scanning electron microscopy with a new type YAG-detector
1Integrated Microscopy Resource for Biomedical Research, University of Wisconsin-Madison 53706.
Scanning Microscopy
|June 1, 1991
Summary
A new double layer coating method enhances high-resolution scanning electron microscopy (SEM) imaging of biological samples. Optimizing accelerating voltage (Vo) improved contrast for backscattered electron (BSE) imaging, revealing detailed 3D structures.
Area of Science:
- Microscopy
- Biological Imaging
- Materials Science
Background:
- High-resolution scanning electron microscopy (SEM) of large biological samples requires specialized coating and imaging techniques.
- Backscattered electron (BSE) imaging of thin metal coatings yields low signals, necessitating field emission SEMs and sensitive BSE detectors.
- Previous methods struggled with contrast for certain sample types, limiting detailed structural analysis.
Purpose of the Study:
- To improve the double layer coating method for enhanced backscattered electron (BSE) imaging in high-resolution SEM.
- To investigate the impact of coating techniques and accelerating voltage (Vo) on image contrast and resolution.
- To demonstrate the potential of an improved BSE detector and field emission SEM for biological sample analysis.
Main Methods:
- Utilized an improved YAG-type BSE detector with an in-lens field emission SEM.
- Prepared cryo-samples: cultured kidney cells coated with platinum-carbon and carbon; and Paramecium trichocyst matrixes coated with platinum and carbon.
- Varied coating methods (unidirectional shadowing, rotation/tumbling sputtering) and primary beam accelerating voltage (Vo) from 4 kV to 10 kV.
Main Results:
- High contrast was achieved for unidirectionally coated kidney cells at Vo ≥ 10 kV.
- Trichocyst matrixes with uniform platinum coating showed poor contrast at higher Vo due to reduced BSE signal from the thin layer.
- Lowering Vo to 4 kV significantly improved contrast for trichocyst matrixes by increasing BSE scattering from the platinum layer.
Conclusions:
- Optimizing accelerating voltage (Vo) is crucial for achieving good contrast in BSE imaging with double layer coatings.
- The improved BSE detection method provides high-resolution, 3D structural information comparable to transmission electron microscopy but with better overall visualization.
- This approach offers a valuable tool for detailed analysis of biological ultrastructures, such as the globular particles and fibrous connections in trichocyst matrixes.