An instrumental technique that measures the elemental and molecular composition of solid materials. Secondary ion mass spectrometry also provides methods of visualizing the two- and three-dimensional composition of solids at lateral resolutions approaching several hundred nanometers and depth resolutions of 1–10 nm. This technique employs an energetic ion beam to remove or sputter the atomic and molecular constituents from a surface in a very controlled manner. The sputtered products include atoms, molecules, and molecular fragments that are characteristic of the surface composition within each volume element sputtered by the ion beam. A small fraction of the sputtered atoms and molecules are ionized as either positive or negative ions, and a measurement by secondary ion mass spectrometry determines the mass and intensity of these secondary ions by using various mass analysis or mass spectrometry techniques. In this technique, the sputtering ions are referred to as the primary ions or the primary ion beam, while the ions produced in sputtering the solid are the secondary ions. Most elements in the periodic table produce secondary ions, and secondary ion mass spectrometry can quantitatively detect elemental concentrations in the part per million to part per billion range by using appropriate standards and specialized analytical conditions. Mo­lecular detection limits by secondary ion mass spectrometry range between 0.1% and part-per-million concentration levels.