Scanning electron microscope (SEM) images the interaction between electron beam and sample, which requires high conductivity, surface smoothness, and cleanliness of the sample. Different materials require targeted treatment, and practical techniques are provided from three aspects: metal, non-metal, and biological samples.

Metal samples: Conductivity and surface cleanliness are key

Metal samples have good conductivity, but surface oxidation or contamination can interfere with imaging. Processing steps:

Cutting and inlaying: For large metal samples, use wire cutting or grinding wheel to cut them into small pieces for easy observation; Brittle metals (such as ceramicized metals) need to be fixed by cold embedding (such as epoxy resin).

Mechanical polishing: Use sandpaper (400 # to 2000 #) for rough grinding, and then use alumina or diamond polishing paste to polish to the mirror surface to reduce surface scratches.

Cleaning: Ultrasonic cleaning for 5-10 minutes to remove polishing residue, then dehydrate with ethanol or acetone to avoid oxidation.

Conductive treatment (optional): If the conductivity of the sample is poor (such as high carbon steel), a thin layer of gold (5-10nm) or carbon film can be plated to enhance signal reception.

Non metallic samples: enhancing conductivity and stability

Non metals (such as ceramics and polymers) have poor conductivity and need to focus on addressing the charge effect. Handling skills:

Coating: Spray a layer of gold, platinum, or carbon (thickness 2-20nm) on the surface to form a conductive path.

Drying treatment: Biopolymer samples require gradient dehydration (ethanol or acetone series), followed by critical point drying (CO ₂ supercritical dryer) to avoid shrinkage and deformation.

Surface conductivity: For porous materials such as activated carbon, conductive adhesive or silver paste can be impregnated to fill the pores.

Biological samples: maintaining a balance between structure and conductivity

Biological samples (such as cells and tissues) need to balance morphological preservation and conductivity. Core steps:

Fixation: Fix the cell structure with glutaraldehyde or formaldehyde to prevent deformation during observation.

Dehydration: Gradient dehydration with ethanol or acetone (30% -100%), 10-15 minutes per step.

Critical point drying: avoids structural collapse caused by surface tension and preserves the three-dimensional morphology of cells.

Coating: Spray a thin layer of gold or platinum (2-5nm) to reduce the charge effect while maintaining surface details.

General recommendation: All samples should be dried with high-purity nitrogen gas after preparation to avoid water stains; Before coating, ensure that the surface of the sample is clean, otherwise uneven coating will affect the imaging quality. By targeted processing, the resolution of SEM images can be significantly improved, providing reliable data for material analysis and biological research.