What is SIMS?

What is SIMS?

SIMS = Secondary Ion Mass Spectrometry

What is SIMS really?

A brief introduction.

SIMS is an measurement technique that is being used for the compositional analysis of small samples. In a SIMS instrument (or "ion microprobe") a high energy primary ion beam is directed at an area of the sample whose composition is to be determined.

The interaction of the primary ions with the sample surface ("sputtering") has three major effects: (1) It leads to a mixing of the upper layers of the sample, resulting in an amorphization of the surface; (2) atoms from the primary ion beam are implanted in the sample and (3) some secondary particles (atoms and small molecules) are ejected from sample. Among the ejected particles are electrically neutral, as well as positively and negatively charged species. Charged particles of one polarity ("secondary ions") can then be extracted from the sputtering area with the help of an electrical field between the sample and an extraction lens. These accelerated secondary ions constitute a secondary ion beam which is then led into a mass spectrometer. There, the secondary ions are sorted by mass (and energy) and finally counted in an ion detector (which can be an electron multiplier,a Faraday cup or a channel plate). The count rates of different secondary ion species give information about the composition of the sample in the sputtered area. Since the size of the sputtered area depends only on the primary ion beam diameter, which typically is in the order of micro-meter, a SIMS analysis has a relatively high lateral resolution.

SIMS can be used for practically all elements of the periodic table, including hydrogen. (Only the noble gases are difficult to measure because they don't ionize easily.) SIMS allows the routine measurement of many trace elements at very low concentration (ppb-range). And since ions of different mass are measured separately, SIMS is ideally suited for the study of isotopic compositions of small samples.

During a measurement, the sample is slowly sputtered (eroded) away and that is why SIMS is capable of measuring depth profiles and perform 3-D measurements.

More Information

There are several sites that have more detailed information on the SIMS technique and its application which are mentioned further below. But of course, there also are other pages at this site that describe the SIMS instruments that we use in our own Laboratory for Space Sciences: The new NanoSIMS and the Cameca ims 3f. Since much of the research we do makes use of the SIMS instruments, our research pages describe many applications of this technique. If you would like to know who else is using SIMS instruments worldwide, you can find many links at our Other SIMS Groups page. And finally, if you work in mass spectrometry, you may find this Isotope Abundance Table useful.

SIMS Links

The Secondary Ion Mass Spectrometry Home Page. This is the mother ship of all SIMS sites with lots of links, technical information and even a SIMS user directory. From here you can also find your way to the SIMS listserver.

A good technical tutorial on SIMS and related techniques can be found in the Ron Fleming Collection which is hosted at Charles Evans & Associates.

Since both of our instruments were made by the same manufacturer, we should also not forget to mention the CAMECA France web site.

Home Page of the Laboratory for Space Sciences

SIMS = Secondary Ion Mass Spectrometry

What is SIMS really? A brief introduction.	SIMS is an measurement technique that is being used for the compositional analysis of small samples. In a SIMS instrument (or "ion microprobe") a high energy primary ion beam is directed at an area of the sample whose composition is to be determined. The interaction of the primary ions with the sample surface ("sputtering") has three major effects: (1) It leads to a mixing of the upper layers of the sample, resulting in an amorphization of the surface; (2) atoms from the primary ion beam are implanted in the sample and (3) some secondary particles (atoms and small molecules) are ejected from sample. Among the ejected particles are electrically neutral, as well as positively and negatively charged species. Charged particles of one polarity ("secondary ions") can then be extracted from the sputtering area with the help of an electrical field between the sample and an extraction lens. These accelerated secondary ions constitute a secondary ion beam which is then led into a mass spectrometer. There, the secondary ions are sorted by mass (and energy) and finally counted in an ion detector (which can be an electron multiplier,a Faraday cup or a channel plate). The count rates of different secondary ion species give information about the composition of the sample in the sputtered area. Since the size of the sputtered area depends only on the primary ion beam diameter, which typically is in the order of micro-meter, a SIMS analysis has a relatively high lateral resolution. SIMS can be used for practically all elements of the periodic table, including hydrogen. (Only the noble gases are difficult to measure because they don't ionize easily.) SIMS allows the routine measurement of many trace elements at very low concentration (ppb-range). And since ions of different mass are measured separately, SIMS is ideally suited for the study of isotopic compositions of small samples. During a measurement, the sample is slowly sputtered (eroded) away and that is why SIMS is capable of measuring depth profiles and perform 3-D measurements.

More Information	There are several sites that have more detailed information on the SIMS technique and its application which are mentioned further below. But of course, there also are other pages at this site that describe the SIMS instruments that we use in our own Laboratory for Space Sciences: The new NanoSIMS and the Cameca ims 3f. Since much of the research we do makes use of the SIMS instruments, our research pages describe many applications of this technique. If you would like to know who else is using SIMS instruments worldwide, you can find many links at our Other SIMS Groups page. And finally, if you work in mass spectrometry, you may find this Isotope Abundance Table useful.

SIMS Links	The Secondary Ion Mass Spectrometry Home Page. This is the mother ship of all SIMS sites with lots of links, technical information and even a SIMS user directory. From here you can also find your way to the SIMS listserver. A good technical tutorial on SIMS and related techniques can be found in the Ron Fleming Collection which is hosted at Charles Evans & Associates. Since both of our instruments were made by the same manufacturer, we should also not forget to mention the CAMECA France web site.

	Home Page of the Laboratory for Space Sciences