World-first accreditation for counting atoms by ion beam analysis
The University of Surrey Ion Beam Centre (IBC) has achieved accreditation for a technique used to count atoms in thin films non-destructively, and with unprecedented accuracy.
The method, Rutherford Backscattering Spectrometry (RBS), received ISO17025 accreditation by UK Accreditation Services at the end of November. This follows a paper published in Royal Society of Chemistry publication ‘Analyst’ by Professor Chris Jeynes and Dr Julien Colaux, which demonstrated that RBS qualifies as a ‘primary direct reference method’ (the sort of method that underpins all accurate measurement) for measuring the quantity of material in thin films.
RBS is at the heart of the work of the IBC , which is a world leader in ion implantation research (the process of implanting atoms into materials using high energy ion beams). RBS enables scientists to count the atoms being introduced to active areas of semiconductor devices, analysing thicknesses equivalent to around one hundredth of a single layer of atom. One of the key uses of implantation is in the manufacture of computer microchips, since these depend on the electronic activity within their ultra-thin surface layers. Such layers are of huge technological importance, and more accurate measurement methods are very valuable.
RBS was first discovered by Lord Ernest Rutherford in 1911 – at a time when the structure of atoms was not yet known – and has been thought to be accurate since 1967 when it was used by radiochemist Anthony Turkevich to analyse moon rocks collected by the Surveyor V space mission.
A world first for any ion beam analysis laboratory worldwide, the accreditation of RBS is important for a number of reasons. Not only are there very few primary direct reference methods available, there are even fewer that can be applied to thin films and are also non-destructive, both of which apply to RBS.
Professor Jeynes says, “The accreditation is a positive step forward for the huge semiconductor industry worldwide but also for many other industries where the functionality of a material is contained within the surface, such as non-reflective glass, coatings and lubricants. This accreditation provides important reassurance to industrial companies wanting to ensure absolute accuracy when developing new processes. An immediate benefit will be in our provision of SIMS (Secondary Ion Mass Spectrometry) ion implanted reference standards – which we are frequently asked to do for academic and industrial partners – as this accreditation directly establishes their quality.”
“As RBS enables measurement without destruction of the sample, it opens the door to applications where further measurements need to be made, or cases where it is essential the sample remains intact.”
Read more about Professor Jeynes’ and Dr Colaux’s paper, ‘Certified ion implantation fluence by high accuracy RBS’, published by ‘Analyst’ in July 2015, and highlighted in the ‘Analytical Sciences in the UK’ collection.
Surrey's RBS accreditation has also recently been featured in TheConversation.
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