On the Accuracy of Compositional Quantification for Atom Probe Tomography

Atom probe tomography (APT) is a versatile technique for characterization of materials with a sub-nm resolution possessing exceptional possibilities for measuring composition on a very small scale, in three dimensions. As the method relies on detection of individual ions that have been field evaporated from a needle-shaped sample, quantification is based on counting atoms. Therefore, no calibration factors are involved and the sensitivity is the same for all elements (with the exception of hydrogen, where ions originating from the sample cannot be distinguished from ions originating from the vacuum). The accuracy of compositional measurements is generally very high, and often the errors given are very small. For example an error of 0.01 at.% is common, suggesting that the relative error for an element of concentration 10% is as small as 10 -3 . Here, a few factors that may deteriorate the accuracy are discussed.