The device was purchased in 2023 with FFG funds for research and development infrastructure support, opens an external URL in a new window.

The M6 Plus, opens an external URL in a new window model from IONTOF, opens an external URL in a new window is a time-of-flight secondary ion mass spectrometer (ToF-SIMS) combined with a scanning probe microscope (SPM). The vacuum system is usually divided into two chambers: the analysis chamber, which also houses the SPM, and a load lock (LL) through which the samples are introduced. Our device also has a third chamber, the preparation chamber (PC) including four connection options to which chambers for experiments or a vacuum suitcase for sample transfer under vacuum can be connected.

The time-of-flight secondary ion mass spectrometer essentially consists of the primary ion source (liquid metal ion gun, LMIG), a sputter source (dual source ion column, DSC) for creating depth profiles, and a reflectron time-of-flight analyser (ToF).

The LMIG is an ion source consisting of a BiMn alloy. It can achieve pulsed ion currents of up to 40 pA and a lateral resolution of 50 nm.

Unlike its predecessor models, the new ToF analyser offers higher mass resolution and up to three times higher sensitivity. The mass accuracy is also within a range of less than 10 ppm.

The DSC consists of two different ion sources. The first is an electron impact gas ion source that can be operated with either Oxygen, Argon or Xenon. In addition to this, a Caesium source is also installed. These sources are mainly used for depth profiles in inorganic samples.

In addition to the main components, an electron source for charge compensation is also installed.

The combination of these components enables various measurement modes with different advantages and disadvantages:

• Surface spectrometry:
  • quasi non-destructive for the outer monolayers
  • information about elemental and molecular composition
  • sensitivity: parts per million (ppm) / parts per billion (ppb)
• Surface imaging:
  • chemical surface mapping
  • lateral distribution of elements/molecules
  • lateral resolution: down to 50 nm
• Depth profiling:
  • in-depth distribution analysis
  • elemental/molecular information
  • depth resolution: <1 nm
  • analytical distance from few nanometers (nm) to several micrometers (µm)
• 3D analysis:
  • defect analysis (buried particles, diffusion channels,..)
  • material science (grain boundaries, diffusion,..

The scanning probe microscope (SPM) is also located in the analysis chamber. For this reason, a piezo-driven sample stage was installed, which can move samples between positions in the ToF-SIMS and SPM with sub-micrometre accuracy at speeds of up to 10 mm/s.

The SPM can be used for all standard applications, such as atomic force microscopy (AFM) or Kelvin probe force microscopy (KPFM). The combination of ToF-SIMS analyses of surfaces and topography measurements using the SPM enables true three-dimensional chemical mapping. The maximum area that can be scanned at once with the SPM is 80 x 80 x 10 μm³, although larger areas are possible with successive measurements. 
 

Focused ion beam (FIB)

Very rough samples, samples with cavities and samples that exhibit strong local differences in density and sputter yield pose a major problem for 3D analysis using SIMS depth profiles. For this reason, an additional ion source, a so-called gallium FIB (focused ion beam), was added to our device. This is used to produce craters on the sample surface and then generate a SIMS image of the crater walls. In addition, 3D tomography images can be created by alternately ‘cutting’ the surface with the FIB and performing 2D SIMS measurements.

Gas cluster ion beam (GCIB)

The gas cluster ion beam (GCIB) installed on our ToF-SIMS allows the gentle removal of organic contamination from inorganic materials and the creation of depth profiles of organic materials (e.g. polymers) under mild conditions. The GCIB can be operated with either Argon or Oxygen. Cluster sizes can be varied between 500 and 10,000.

Heating and cooling

Our system has an in situ heating and cooling option. The sample holder is cooled or heated not only in the analysis chamber, but already in the load lock. The temperature range extends from -130°C to 600°C.

Gas inlet

Gas, such as Argon, can be blown onto the samples in the analysis chamber through a gas inlet. This is primarily used for charge compensation.

Transfer vessel

The transfer vessel can be used to transfer samples in an airtight environment, for example from a glove box to the ToF-SIMS. To do this, the transfer vessel is closed in the glove box and only reopened in the load lock.