Ion Irradiation Modification of Silicon Nanowires

Ion irradiation modification of silicon nanowires has been explored in-situ using the Microscope and Ion Accelerator for Materials Investigations (MIAMI) facility at the University of Huddersfield. Ion irradiation experiments were designed using the Stopping and Range of Ions in Matter (SRIM) Monte Carlo computer code. A multislice SRIM method was developed to estimate the damage and ion implantation in a nanowires geometry and a code was developed to incorporate SRIM into MatLab.

In-situ Transmission Electron Microscopy (TEM) has been used to explore the ion-beam-induced bending of silicon nanowires under different irradiation conditions and the underlying mechanisms which drive nanowire bending have been identified. Furthermore, a tipping point for direction reversal of bending under different irradiation conditions has been identified. Recrystallisation of silicon nanowires was also investigated using thermal annealing.

The effects of 7 keV Xe+ ions on silicon nanowires have been investigated under industrial processing conditions. Structural and morphological changes of silicon nanowires have been observed. These include nanowire bending, amorphisation, bubble formation and sputtering. The depth of damage has also been measured experimentally and was compared with the predictive damage using SRIM.

In order to calculate the temperature along a nanowire during an in-situ TEM heating experiment, the relevant parameters have been found from the literature which will be used to set up a finite element model. Atomic Force Microscopy (AFM) was used to measure the surface roughness of silicon nanowires and molybdenum grids. Other parameters of interest include the Hamaker’s constant for the Van der Waals forces as well as the Young’s modulus, thermal conductivity and specific heat capacity of silicon nanowires and the ultra-thin oxide layer on their surface.