Electron Microscopy Applications Quiz

Electron Microscopy

• Electron Microscopes use a beam of highly energetic electrons to examine objects on a very fine scale.
• They provide information about the topography, morphology, composition, and crystallographic information of samples.

Types of Electron Microscopes

• Transmission Electron Microscope (TEM): allows for the study of inner structures of thin samples supported on TEM grids.
• Scanning Electron Microscope (SEM): used to visualize the surface of objects of any thickness mounted on an aluminum stub.

Differences between TEM and SEM

• TEM: electron beam passes through thin sample.
• SEM: electron beam scans over the surface of the sample.

TEM

• Total magnification is a combination of the magnification from the objective lens, intermediate lens, and projector lens.
• Each lens is capable of approximately 100X magnification.

SEM

• Produces images of a sample by scanning it with a focused beam of electrons in a raster scan pattern.
• Electrons interact with atoms, producing signals that contain information about the sample's surface topography and composition.

Characteristics Viewable on SEM

• Topography: surface features of an object, directly related to materials properties.
• Morphology: shape and size of particles making up the object, directly related to materials properties.
• Composition: elements and compounds that the object is composed of, directly related to materials properties.
• Crystallographic Information: arrangement of atoms in the object, directly related to materials properties.

Forensic Applications

• Trace evidence analysis: examines morphology, composition, and structure of fibers, hairs, dust particles, etc.
• Firearm and Tool Mark Examination: studies microstructure of tool marks, striations, and microscopic features on bullets, cartridge cases, and other ballistic specimens.
• Forensic Pathology: provides detailed images of cellular structures and organelles, aiding in the investigation of injuries, diseases, and causes of death.
• Document examination: detects forgeries, analyzes counterfeit currency, and determines the authenticity of documents by studying ink composition, paper fibers, and printing techniques at the nanoscale.