Principle

An SEM is essentially a high magnification microscope, which uses a focussed scanned electron beam to produce images of the sample, both top-down and, with the necessary sample preparation, cross-sections. The primary electron beam interacts with the sample in a number of key ways:-

• Primary electrons generate low energy secondary electrons, which tend to emphasise the topographic nature of the specimen
• Primary electrons can be backscattered which produces images with a high degree of atomic number (Z) contrast
• Ionized atoms can relax by electron shell-to-shell transitions, which lead to either X-ray emission or Auger electron ejection. The X-rays emitted are characteristic of the elements in the top few μm of the sample.

Applications

The SEM instrument has many applications across different industry sectors. The extremely high magnification images together with localised chemical information means the instrument is capable of solving a great deal of common industrial issues such as particle analysis, defect identification materials and metallurgical problems.

LPD Lab Services has extensive experience in using SEM/EDX in the following industrial sectors; electronics and semiconductor, pharmaceutical, petrochemicals, plastics and polymers and many others.

Please see the specific applications to the left and the general list below. Please do not hesitate to contact us to discuss your requirements.

Range of materials:-

• Metals, Glass and Ceramics
• Semiconductors
• Plastics
• Powders and Dust
• Fibres (Textile, glass, asbestos, natural)

Range of applications:-

• Classification of materials
• Failure and defect analysis
• Examination of surface morphology (including stereo imaging)
• Analysis and identification of surface and airborne contamination
• Powder morphology, particle size and analysis
• Cleaning problems and chemical etching
• Welding and joining technology
• Paints and coating failures
• Identification and elimination of corrosion and oxidisation problems.

Examples Applications / Case Studies

Image Magnification, Measurement and Resolution

The image is of the surface of a metal stamper used to imprint the information onto a compact disc during manufacture.

The image was taken at a magnification of X 40,000 on the SEM. The photograph illustrates the shape and structure of individual bits of information. The height, roughness and steepness of the sidewalls of the information are all critical to the manufacture of a good disc, as is the separation between adjacent tracks.

The second image is of a fracture section through a pellet made of tungsten powder that has been sintered and then sputter coated with an alloy of osmium and ruthenium.

The output from both the secondary electron and backscatter detectors has been mixed together on the SEM to highlight the sputtered layer on the surface of the pellet. This enables accurate measurement of the thickness of the sputtered layer and shows the growth structure through the layer. The thickness of the layer was measured at 640 nm.

Analysis of Thin Films

EDX analysis was carried out on a thin evaporated layer on top of a nickel / iron alloy.

The layer contained a mixture of barium, strontium and oxygen, with a small amount of magnesium. The thickness of the layer was calculated to be ~ 38 nm.

Our site expert on SEM/EDX Spectrometry is Keith Raper.