Time-of-flight secondary ion mass spectrometry in the helium ion microscope

A helium ion microscope, known for high resolution imaging and machining with helium or neon ions, has been equipped with a time-of-flight spectrometer for in-situ compositional analysis.
Here we report on its design, implementation and show first results of this powerful add-on.
Our design considerations were strongly based on detailed simulations of the ion collision cascade with a focus on the physically achievable resolution for the various detection limits.
Based on these simulations different secondary ion extraction systems and spectrometer types are considered and compared with respect to the demands and limitations of the microscope.
As a result the development and examination of a straight secondary ion extraction and a time-of-flight spectrometer is reported that allows the simultaneous measurement of all secondary ion masses.
First experimental results demonstrate an excellent mass resolution as well as high-resolution secondary ion imaging capabilities with sub-8 nm lateral resolution.
High resolution secondary electron images correlated with in-situ mass-separated sputtered ion distributions have a high potential to answer open questions in different fields of materials science.