Structural characterization of thin carbon films on high-current silicon field emitters

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Adaptix is a SME based at the Oxford University Science Park that develops low-cost, low-dose, portable 3D x-ray sources. The core technology is a 'Distributed Array' that digitises the source, replacing a single high-power tube with a multitude of addressable low-power emitters in conjunction with modern Flat Panel Detectors). Thus 2D diagnostics is replaced with 3D (digital tomosynthesis) in the acute care setting (A&E, ICU), and into Primary Care, improving initial diagnosis overall.Adaptix is currently selling its units for veterinarians, and is expanding its technology for the Non-Destructive Evaluation applications and for its biggest market, ortho x-ray imaging, chest and dental. For some applications it needs to increase the brightness of its panel x-ray source, e.g in chest imaging, because of the thickness of the human chest, with overlaying different types of tissue, bone, muscle etc.The development of the emitters' array by novel etching and coating technologies is Adaptix' current priority. For the theoretical background we are collaborating with leading experts in the modelling and characterization of field emitters from the Universities of Tartu and Lyon in France.Preliminary experiments on an inert coating on the silicon emitters held very promising results in terms of the improved current emission (3x) and its stability.In collaboration with the University of West Scotland and STFC in Daresbury we are investigating various methods for the fabrication of this inert coating. Initial results exhibit a huge variation in the performance of the emitters. We ascribe this to the film composition and structure, known to vary a lot among different coating techniques, but we have not the means to characterise that.The increased current emission (2-3X) and the improved lifespan that we observe in some of the coated samples would be a real game changer for our technology and open new markets for us.Analytical tools to characterise the exact structure and composition of the coatings are not easily available and Adaptix does not have the acute scientific know-how, analysis or facilities for the required measurements.In collaboration with NPL we hope to be able to understand the composition of our coatings. With this we aim for reproducible, stable results. An additional goal is also to develop a method for quality control in our production facility.