Ionic liquids for subtractive and additive nanomanufacturing

I propose investigating the use of ionic liquids for materials treatment, specifically in nanotechnology. Nanotechnology is the manipulation of matter at molecular scales close to one billionth of a meter. Progress in manufacturing at this scale has enabled the fabrication of modern electronic and biomedical technologies. However, more advanced processes are required to manufacture even faster computers, better drug delivery systems, and many other future technologies. In this project, ionic liquids will be used to access new options for these manufacturing processes. These exciting new liquids have been developed over the last two decades for a range of chemistry and energy storage applications. Ionic liquids consist entirely of charged complex molecules (ions) at room temperature, which allows for a new approach to nanotechnology manufacturing with a device known as an Ionic Liquid Ion Source (ILIS). In an ILIS, the ionic liquid covers a sharp needle. By applying a high voltage to this needle, it is possible to produce a beam of ions from the liquid. This spray can be directed towards a material for treatment. Different ion combinations would be available for various materials processing applications, as ionic liquids have been extensively studied, and hundreds of stable compositions have been discovered. For example, the beam can contain reactive ions, and can be used to remove material from silicon, a common material used in microprocessors. Varying the beam conditions and composition can allow for both the erosion of material (subtractive method) and the deposition of a thin film on the surface or to create a structure (additive method). I will explore the interactions of the ILIS beam with different materials, study the use of ILIS for material removal and deposition, and investigate the possibility of focusing the beam of ILIS for careful processing of materials at the nanoscale.

In the first stage of this fellowship (2020-2024) a vacuum chamber was constructed; this chamber is being used for detailed characterization of emission from different ionic liquids. ILIS beams are comprised of several different ion types, and so a filter is being used to separate these components. The separate ion types are being fired towards a variety of materials to understand how specific ions react with different targets. These fundamental studies are being complemented by experiments that use an ILIS to remove material and create a nanoscale pattern. Additional experiments can be performed with an array of ILIS devices, in order to achieve higher throughput. The possibility of depositing thin films of ionic liquids from an ILIS beam is also under study. The fellowship is developing a focused ion beam (FIB) from an ILIS; FIB machines take the beam of particles from an ion source and focus the particles onto a nanometre sized-spot on a target, thus allowing localized modifications to a sample. Computer simulations are being used to design a bespoke focusing setup in which the ILIS is being installed.

In the renewal stage of the fellowship (2024-2027), experiments will be undertaken to quantify how well the ILIS-FIB beam is focused, using different ionic liquids and different operating conditions in the focusing setup. The ILIS-FIB platform will be used in several applications, for instance microscopy or precise milling at the nanoscale. Another avenue of research will be to study the possibility of creating three-dimensional nanostructures by depositing material with the focused ion beam of ionic liquid particles.