Ionic Liquid Irradiation

This project will study the material treatment capabilities of a device known as an Ionic Liquid Ion Source (ILIS). Ionic liquids are room temperature molten salts, or mixtures of cations and anions that are liquid at room temperature with no intervening solvent. In an ILIS, an 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.

The ILIS beam can be fired towards a material for treatment. Many different ion chemistries are available for various materials processing applications, as hundreds of ionic liquids have been discovered. For example, the beam can contain reactive ions, which can be used to etch (remove) material from a substrate. ILIS has been demonstrated to etch silicon, a material commonly used in microelectronics.

Previous studies reveal that the beams from ILIS contain several types of ions with different chemical compositions. For material treatment applications, it is desired to use only a specific type of ion. The goal of this doctoral project is to characterise the interactions between different types of ions and target materials at different irradiation conditions, by using a special filter, knows as a Wien filter, to select specific components of the ILIS beam.

The outcomes of this project will be of academic and commercial importance and use. Results will be shared through publications in high-impact factor journals and participation in world-class conferences. Characterising the material treatment performance of ILIS could allow us to develop useful technologies, for an example, an ILIS etching machine, which could be commercialised. Currently, state-of-the-art etching machines rely on generating a plasma from toxic gases; these plasma etchers are bulky and require many safety measures for their operation. As ionic liquids are non-volatile, an ILIS etcher would provide a safer, more compact alternative for use in material removal in research and industry.
Design and implement a Wien filter for separation of the different components of an ILIS beam.
Use the filtered beam from an ILIS to irradiate materials, to characterise and compare the effect of the different components of the beam when they impinge on a substrate.

In this project, the student will, use COMSOL Multiphysics simulations to design a Wien filter for separation of different ion species contained in the beam. Construct and implement this Wien filter in a vacuum chamber. Test the filtering system with ILIS, using techniques such as time-of-flight spectrometry and retarding potential analysis to determine the composition and energy distribution of the beam.
Irradiate samples of different materials, including semiconductors and biological substrates, and evaluate the result of irradiation using profilometry, atomic force microscopy, and x-ray photoelectron spectroscopy.

Pursuing these objectives will help develop a new technique for materials treatment based on Ionic Liquid Irradiation.
This project is most closely aligned with EPSRC's "Manufacturing Technologies" research area.