Tracking Ångstrøm Scale Evolution of Solid Films and Nano Crystals via Transmission Electron Microscopy

Atomic Layer Deposition (ALD) is dictated by chemical principles that allows films to grow in a binary fashion, one monolayer at a time. Films are smooth, dense and of equal thickness, even when they cover complex geometries. Modern semiconductor materials, catalysts, computer memory, fuel cell electrolytes and battery cathodes are just a few examples where ALD plays a significant and ever-growing role in the production of electronic devices surrounding us today.
Continuous miniaturization steadily increases the performance and functionality of electronic devices. Performance gains so far have followed Moore’s law, the observation that the number of transistors in a dense integrated circuit doubles approximately every two years. It is one of the greatest achievements in human history and still applies, due to the unprecedented research and development efforts in this field. The International Roadmap of Semiconductors’ strategy is to introduce films below 10 nm in 2017 and even below 5 nm in 2020 in order to keep this industry sector growing at its stipulated pace. ALD is the only technology providing atomic scale control over such ultrathin films; therefore, it will be even more important in the future. Yet, the growth of films in the 5-10 nm range is still challenging. In the initial phase, the so-called nucleation phase, many factors influence growth. This phase varies significantly among different substances related to their chemical and physical properties. Investigating these properties is very challenging since the information has to be gathered during film growth at working conditions. This means that we have to measure the film in a vacuum and at high temperatures with atomic scale resolution to get insight into the actual growth process occurring. We have to analyse tiny quantities of material (one atomic layer at a time), which makes it impossible to utilize most of the characterization tools we have at hand today.

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Pt Nanoparticle growth with ALD and PEALD [2]


Crystal peak shift of Barium Titanate thin films with Barium content and respective decrease in Leakage current [6]