Fabrication and Characterization of Nanoscale Needle Specimens in a Cryogenic Environment.

This thesis aims to develop an approach to fabricate vitreous ice-needle tips with ~150 nm diameters at the cryogenic temperature (< -155 ℃), for the high-resolution characterisations while preserving the hydrated samples such as biological specimens in their near-native state. The nanoscale tip geometry allows high-resolution characterisations such as atom probe tomography (APT), which can provide 3-D chemical composition maps with a near-atomic resolution. A coating technique has also been developed to produce a nanoscale electrically conductive coating layer at the tip geometry to facilitate the characterisations. This study paves the way for near-atomic APT imaging of biological cells in their near-native state.