Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is a surface analytical technique used for obtaining elemental and molecular chemical information about surfaces (static SIMS), as well as, detecting part per billion (ppb) concentrations of impurities in semiconductors and metals (dynamic SIMS). All elements, including hydrogen, are detectable by SIMS.

In ToF-SIMS analysis, the sample is placed in an ultrahigh vacuum environment where primary ions bombard and sputter atoms, molecules, and molecular fragments from the sample surface. The mass of the ejected particles (i.e. secondary ions) are analyzed via time-of-flight mass spectrometry.

In the ToF analyzer, ejected ions are accelerated into the analyzer with a common energy (but different velocities depending on the particle mass). Due to the differences in velocities, smaller ions move through the analyzer more rapidly than the larger ions. The mass of the secondary ions are determined by their travel time through the analyzer. SIMS is a surface sensitive analysis method since only the secondary ions generated in the outermost 10 to 20 Å region of a sample have sufficient energy to overcome the surface binding energy and escape the sample surface for detection and analysis.

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Mass spectrum - Identifies the elemental and ion composition of the uppermost 10 to 20 Å of analyzed surface from positive and negative mass spectra. The high resolution of the ToF analyzer can distinguish species whose masses differ by only a few millimass units.

Depth profile - During SIMS analysis, the sample surface is slowly sputtered away. Continuous analysis obtains composition information as a function of depth. Depth resolution of a few Å is possible. High sensitivity mass spectra can be recorded or reconstructed at any depth of the depth profile.

Secondary ion mapping - Measures the lateral distribution of elements and molecules on the surface. To obtain a SIMS map, a highly focused primary ion beam is rastered across the sample surface, and the secondary ions are collected at specific points. Image brightness at each point is a function of the relative concentration of the mapped element or molecule. Lateral resolution is less than 100 nm for elements and 0.5 µ for large molecules.

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• Identifying lubricants on magnetic hard discs
• Measuring dopant distributions in semiconductors
• Profiling thickness of insulating films on glasses
• Mapping elemental and molecular patterned surfaces
• Identifying compounds in thin organic films
• Extent of crosslinking in polymers

Sample size cannot exceed 3.5 in. (85 mm) in any lateral direction. Height should not exceed 0.8 in. (20 mm). Sample must be compatible with high vacuum environment (<1x10-9 Torr).

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