Depth profiling is the measurement of the uppermost surface layers of a sample’s chemical content, which is typically carried out in ultra-high vacuum (UHV) surface analysis applications to determine the atomic composition and sorption behavior of a given material.
UHVs are a prerequisite for the majority of surface science experiments to ensure high sample purity throughout, maintaining a contaminant-free state for the most accurate results. It also reduces gas phase interference during experiments using ion-based techniques. This is crucial for desorption studies of stimulated electrons and photons with low energy ions, and for a wider range of surface chemistry experiments and studies.
Various mass spectrometers and probes are manufactured to perform depth profiling techniques using beams of ions or plasma, or pulses of laser light to determine the atomic structure and sorption properties of the first few microns or nanometers of surface material. These high brightness ion guns are integrated into mass spectrometers or dedicated surface analysis workstations with multi-function UHV chambers, and built-in optics for beam rastering and direct raster rate for depth profiling.
The equipment required for depth profiling in UHV surface analysis varies, with a range of suitable quadrupole mass spectrometers, ion sources, and fully-integrated workstations available from Hiden Analytical to achieve accurate depth profiling analysis.
Hiden Analytical’s Depth Profiling Products
Hiden Analytical has developed a ‘SIMS workstation’ that uses the high sensitivity technique for accurate analysis known as SIMS Surface Analysis. It comprises one of two primary ion guns from our product catalog for use in depth profiling for surface analysis applications. These ion sources, integrated into the matrix of instruments used in the SIMS workstation, can provide depth profiles with a resolution of two nanometers (nm). Further details of these two ion sources are outlined below:
- IG5C Caesium Ion Gun: The IG5C is a differentially pumped caesium ion gun with a spot size from < 30 µm to > 1mm for highly accurate miniature surface ionization and nanometer depth resolution of surface layers. It is designed for both dynamic and static SIMS applications, with depth profiling capabilities for electronegative elements, and layers formed through deposition and corrosion.
- IG20 Argon / Oxygen Ion Source: The IG20 is a twin filament electron impact ion source with a spot size from < 100 µm to > 1mm of beams produced typically using argon or oxygen gases – although beams can be produced using all noble gases. The twin filament structure allows for simultaneous analysis even during filament replacement, allowing for accurate assessment of surface composition throughout greater periods of sustained ionization.
These ion sources are coupled with a spectrometer such as the MAXIM SIMS detector; a compact spectrometer designed for materials analysis with a wide field of view and mass range options from 1: 50, 1: 1000 amu and up to 5000 amu for clusters. This array is capable of comprehensive depth profiling for surface analysis with fully tunable software provided for the collection of depth profiles of a range of samples.
Surface Analysis Products from Hiden Analytical
Hiden Analytical are experts in the development and production of ion sources and mass spectrometers, with a 35-year reputation for manufacturing quality instruments applicable for a range of scientific fields. Our SIMS workstation is instrumental to the depth profiling of materials in a range of industries.