What is Dynamic SIMS?

SIMS (Secondary Ion Mass Spectrometry) is the most sensitive elemental and isotopic surface microanalysis technique. Dynamic SIMS mode enables you to analyse bulk composition and in-depth distribution of trace elements. Here’s an overview of how it works and what it can be used for.

SIMS vs Dynamic SIMS

SIMS (Secondary Ion Mass Spectrometry) is the most sensitive elemental and isotopic surface microanalysis technique:

• Extremely high sensitivity to all elements from Hydrogen to Uranium and above
• Detection limit down to the ppb level for many elements
• High lateral resolution imaging down to 40 nm
• Very low background for high dynamic range (>5 decades)

Static SIMS focuses solely on the first top monolayer, mostly for molecular characterisation.

Dynamic SIMS mode investigates bulk composition and in-depth distribution of trace elements, with a depth resolution from sub-nm to tens of nm.

All CAMECA SIMS instruments are capable of dynamic SIMS.

How Static SIMS Works

A solid sample is sputtered by primary ions of energy (just a few keV ). Particles are emitted, a fraction of which are ionised. Secondary ion emission is measured using a mass spectrometer.

This provides information about the elemental, isotopic and molecular composition of atomic layers at the surface.

Secondary ion yields vary greatly according to the chemical environment and sputtering conditions, e.g., ion, energy, and angle. This adds complexity to the quantitative aspect of the technique. SIMS is known as the most sensitive elemental and isotopic surface analysis technique.

Which Materials can you analyse?

SIMS can be used to analyse any type of solid material that can be kept under vacuum, including insulators, semiconductors and metals. It’s a destructive technique because it involves sputtering.

Dynamic SIMS Mode

While static SIMS measures only the top monolayer, dynamic SIMS measures bulk composition and the in-depth distribution of trace elements, with a depth resolution of sub-nm to tens of nm.

Dynamic SIMS instruments use primary ion beams of oxygen and caesium. This enhances the positive or negative secondary ion intensity.

The process starts from the surface (or through an interface). By increasing the primary ion dose implanted in the target, the primary species concentration (oxygen or caesium) will reach an equilibrium. This depends on the sputtering conditions and the target material. The equilibrium corresponds to a sputtering steady state. Once it’s reached, reliable quantification is possible with reference standard samples, using Relative Sensitivity Factors.

Applications

Dynamic SIMS is often used to measure the in-depth distribution of trace elements, e.g., dopants or contaminants in semiconductors. Various depths and depth resolutions can be investigated by adjusting the ion impact energy:

• Low energy (down to 150eV) is used to reduce atomic mixing caused by collision cascades and to achieve depth resolution down to the sub-nanometre level.
• High energy (up to 20 keV) is used for deeper analysis (tens of microns), faster sputter rates (µm/min range), and lower detection limits.

Dynamic SIMS is also used for high-resolution imaging analyses and high-precision isotope ratio measurements.

On-Demand Webinar

Find out more about dynamic SIMS in this on-demand webinar from CAMECA. The 20-minute presentation provides an introduction to the technique:

• Primary and secondary beam species
• Relative sensitivity for various elements
• Matrix effects
• Depth and lateral resolution
• Depth profiling (choosing impact energy, sputtering rate and calibration methods)
• Scanning ion imaging mode
• Dynamic SIMS’ key analytical characteristics

It’s presented by Dr Paula Peres, SIMS Product Manager at CAMECA. The recorded webinar is available to watch on-demand on CAMECA’s website:

CAMECA SIMS Range

Blue Scientific is the official distributor for CAMECA in the UK, Ireland and Finland. We offer their entire range of SIMS systems, all of which feature dynamic SIMS:

More Information

If you have any questions or if you’d like a quote, just get in touch:

Contact us on +44 (0)1223 422 269 or info@blue-scientific.com

More about the CAMECA range