A scanning electron microscope (SEM) produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample’s surface topography and composition. The electron beam is generally scanned in a raster scan pattern, and the beam’s position is combined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometer. Specimens are generally observed in high vacuum. The most common mode of detection is by secondary electrons emitted by atoms excited by the electron beam. The number of secondary electrons is a function of the angle between the surface and the beam. On a flat surface, the plume of secondary electrons is mostly contained by the sample, but on a tilted surface, the plume is partially exposed and more electrons are emitted. By scanning the sample and detecting the secondary electrons, an image displaying the tilt of the surface is created. Generally, the primary beam also excites x-ray fluorescence from the atoms in the sample. The intensity of the x-ray fluorescence is used to provide semi-quantitative compositional information about the sample.
Contamination in the manufacturing process often leads to costly production losses. Identifying the contaminant can help pinpoint the source of the problem and minimize negative effects. Constellation has the tools to effectively analyze and identify many types of contamination.
Incoming material inspection and verification is an important part of quality control in the aerospace, automotive and defense industries. Materials used in manufacturing processes are routinely analyzed for adherence to quality specifications, including SAE-AMS and military specifications (MIL-Spec). With an extensive array of analytical instrumentation and experienced chemists and scientists, Constellation can perform incoming chemical and physical tests on a wide range of materials. The laboratory provides testing using US Pharmacopeia, Reagent Chemical, and ASTM methodologies, as well as procedures developed to meet the customer’s
Manufacturers often encounter unknown materials in their processes. Such materials include an unknown substance discovered in the manufacturing process, a suspect material from a new supplier, or a poorly-performing material. Constellation specializes in the identification of most types of materials, including metals, plastics, minerals and liquids. Most materials can be identified based on chemical composition and physical properties. The material identifications can range from extensive analyses to ensure high-quality materials to positive material identification (PMI) screening methods for rapid comparison of unknown materials to known samples.
Constellation can provide analysis of the first several atomic layers of a solid sample using x-ray photoelectron spectroscopy (XPS) and/or Auger electron spectroscopy (AES). These techniques provide semi-quantitative analysis of the composition of the solid surface. These techniques are the instrumental methods of choice for characterization of such things as surface contamination, chemical imperfections and corrosion. Coupling the techniques with inert ion sputtering provides a semi-quantitative composition of the solid sample as a function of depth.