The Qtac
High performance Low Energy Ion Scattering (LEIS)
Quantitative top atomic layer characterisation
The Qtac is a high sensitivity Low Energy Ion Scattering (LEIS) instrument. It is extremely surface sensitive, providing quantitative elemental characterisation of the top atomic layer.

This instrument has been developed to include small spot analysis, surface imaging, and both static and dynamic depth profiling.

Its unique surface sensitivity makes the Qtac the perfect tool to study surface processes. The Qtac provides valuable information in many production and research areas on materials such as catalysts, semiconductors, metals, polymers, and fuel cells.
Key features are
Quantitative, elemental characterisation of the top atomic layer
Spectroscopy, imaging and depth profiling capabilities
Time-of-flight mass filtering for improved sensitivity
Analysis of rough and non-conductive materials
Energy Analyser
The unique Qtac energy analyser design is based on the advanced Calipso technology. At the optimum scattering angle, the analyser has an acceptance over the full azimuth while maintaining a well-defined scattering angle.

This, together with parallel energy detection, simultaneously provides high sensitivity and high mass resolution. The possibility of using heavier noble gas ions, which is usually not possible with conventional ion scattering spectrometers, is essential for unambiguous identification of all elements.

The dedicated analyser design allows for non-destructive, reproducible and quantitative analysis of the top atomic layer.
Noble Gas Ion Gun
Pulsing System
Position Sensitive Detector
Energy Analyser
Focussing Optics
Time-of-Flight Mass Filter
In conventional LEIS, secondary ions, generated by the impact of the noble gas ions, lead to a high background for low scattering energies.

This background reduces dynamic range and detection limits, in particular for light elements.

The Qtac is equipped with a time-of-flight detection system, which separates the scattered noble gas ions from this background. This unique feature significantly improves the elemental detection limits and the dynamic range of the instrument.

LEIS spectrum of a technical polymer without time-of-flight mass filtering
LEIS spectrum of a technical polymer without time-of-flight mass filtering
LEIS spectrum of the same sample with time-of-flight mass filtering showing significantly improved detection limits
LEIS spectrum of the same sample with time-of-flight mass filtering showing significantly improved detection limits
Customised Solution
Close customer collaboration to meet individual needs
In laboratories with various analytical techniques, it is often beneficial to examine the same surface in more than one instrument, without exposing the sample to the atmosphere.

For many samples, e.g. from atomic layer deposition or catalyst preparation, in situ transfer between preparation and analysis is essential to monitor the undisturbed surface.
IONTOF has a strong tradition of collaboration with its customers to incorporate new ideas for hardware and software and to develop solutions for individual needs.
The modular design of the Qtac’s primary ion source and analyser unit is ideal for this kind of customisation.
A large variety of UHV chambers for sample preparation or additional characterisation techniques, designed by our experts for individual customers‘ specific requirements, can easily be added to the instrument. It is also possible to couple the instrument to existing UHV systems, or to integrate only the analytical component (Qtac bolt-on)
Qtac Bolt-on Module
Many materials preparation, surface treatment, and thin layer deposition techniques benefit from on-line quality control and in situ analysis. For coverage and layer thickness measurements, the Qtac makes an ideal addition.

The Qtac is available as a bolt-on system, to be integrated into laboratory instruments or industrial tools. ALD and MBE deposition systems are typical examples.
Home-built UHV system with Qtac bolt-on module
Home-built UHV system with Qtac bolt-on module
LEIS Dual Beam Depth Profiling
The Qtac can be equipped with a high current ion optical column fitted with an Ar electron impact gas ion source. This ion gun is used for ultra-low energy sputtering in combination with LEIS analysis. In this dual beam depth profiling mode high resolution chemical depth profiles are obtained.

In contrast to SIMS, there is no need to use reactive sputter species, which would lead to changes in sputter rate and ionisation yield close to the surface. The Qtac100 provides easy quantification even in the first few nanometres of the profile.

The example shows a LEIS sputter profile through a CrNi multilayer system. The LEIS analysis was done with a 5 keV Ne analysis beam. For sputtering, a 500 eV Ar beam was used. The plot on the right shows the "liniarity" of the "corresponding" correlation plot over the full concentration range very nicely.
LEIS depth profile through a CrNi multilayer
LEIS depth profile through a CrNi multilayer