Atom Probe Tomography

Electron and ion beam technologies (Structural & Morphology Characterization)

Atom probe tomography uses a voltage and/or laser pulse to field evaporate atoms from the end of a specimen in the form of a sharp tip. The tip must have an end radius of less than 50 nm and may be prepared by electro-polishing (metallic samples) or by FIB (other sample types and when site specificity is required). By measuring the time-of-flight and the position of the evaporated atoms on a position sensitive detector a 3-D reconstruction of the position and chemical nature of detected atoms is possible. The technique has sub-nm resolution (around 0.1-0.3nm resolution in depth and 0.3-0.5nm laterally) and detection efficiencies as good as 80%. The mass resolution of a typical instrument is between 1000 to 2000 m/dm. The use of laser pulsing allows metals, semiconductors and insulators to be analysed. However, samples that contain a mix of insulators, semiconductors and metals can be challenging and sample fracture may occur at weak interfaces.

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