ToF-ERDA

Time-of-flight elastic recoil detection analysis (ToF-ERDA) is a quantitative material analysis method that gives concentrations of elements and their depth profiles in a sample. With ToF-ERDA, it is possible to detect all elements and distinguish between different isotopes of hydrogen.

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What is ToF-ERDA used for?

Time-of-flight-elastic recoil detection analysis (ToF-ERDA), also known as elastic recoil detection (ERD), elastic recoil scattering (ERS), and forward recoil spectrometry (FRS), is an ion beam analysis (IBA) technique that is used to determine the elemental concentrations in thin layer materials.

ToF-ERDA can detect all elements as well as different isotopes of hydrogen. It measures the concentration of each element within a sample as a function of depth, generating an elemental depth profile of the sample's surface. Detection limits between 0.1–0.5 atomic percent and depth resolutions of 5-20 nm are usually achieved. Surface layers with 20-500 nm thickness can be characterized with ToF-ERDA. To get reliable results, the sample must have a flat surface and roughness of less than 10 nm.

ToF-ERDA is most commonly used to determine the elemental depth profiles of thin films (metal oxides, nitrides, metals, etc.) on typical substrates, such as silicon (Si), gallium nitride (GaN), silicon carbide (SiC), gallium arsenide (GaAs) or indium phosphide (InP). The technique is handy when developing new thin film deposition methods or optimizing existing processes to understand how changes in the deposition parameters affect the elemental composition of the resulting thin films.

ToF-ERDA is practically the only characterization technique that offers precise and cost-efficient hydrogen quantification simultaneously with quantifying the main components of thin films. The method is inherently quantitative when thin film samples on typical substrates are analyzed, so reference samples are not needed to achieve quantitative results.

What are the limitations of ToF-ERDA?

To get reliable results, the sample must have a flat surface and roughness of less than 10 nm. The detection limit is 0.1–0.5 atomic percent. A more sensitive method, such as SIMS, is needed to detect smaller concentrations. Only inorganic samples are suitable for ToF-ERDA analysis because the heavy ion beam damages organic samples.

How does Tof-ERDA work?

ToF-ERDA uses a heavy ion beam (such as Cl, I, Au) with energies of up to 100 MeV. The energetic ion beam is directed at the sample at a known angle. The beam ionizes the sample atoms and the ions from the sample surface layers recoil in a forward direction. Recoiled ions are then detected.

In ToF- ERDA, the energy and time of flight of the recoil ion are measured simultaneously. Recoiled ions are typically detected with two timing detectors and an energy detector. Filters are used to separate electrons from recoil ions. Time-of-flight is measured with the timing detectors over a fixed distance. The energy detector distinguishes the different masses of the ions. Conversion of time/energy spectra is used to create a depth profile by using the known relationship of energy loss by a unit of length of the ions in the sample.

Need an analysis?

Measurlabs offers high-quality ToF-ERDA measurements, as well as other thin film and semiconductor analyses. Available techniques include GD-OES, RBS, VPD-ICP-MS, and others. You can request a quote using the form at the bottom of the page - we will then get back to you within one business day.

Suitable sample matrices

  • ALD, CVD, PVD or similar thin films
  • Optics
  • Semiconductors
  • Thin films depositted on Si, GaN, SiC, GaAs or InP wafers
  • Metal oxides, nitrides, metals, etc

Ideal uses of ToF-ERDA

  • Elemental analysis and depth profiling of thin films
  • Profiling light elements, such as H, B, C, N and O, in thin films

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Frequently asked questions

What is Measurlabs?

Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.

How does the service work?

When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.

How do I send my samples?

Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.