Pengfei Zhai

Surface Modification and Damage of MeV-Energy Heavy Ion Irradiation on Gold Nanowires

Gold nanowires with diameters ranging from 20 to 90 nm were fabricated by the electrochemical deposition technique in etched ion track polycarbonate templates and were then irradiated by Xe and Kr ions with the energy in MeV range. The surface modification of nanowires was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations. Different craters with and without protrusion on the gold nanowires were analyzed, and the two corresponding formation mechanisms, i.e., plastic flow and micro-explosion, were investigated. In addition, the sputtered gold nanoparticles caused by ion irradiation were studied and it was confirmed that the surface damage produced in gold nanowires was increased as the diameter of the nanowires decreased. It was also found that heavy ion irradiation can also create stacking fault tetrahedrons (SFTs) in gold nanowires and three different SFTs were confirmed in irradiated nanowires. A statistical analysis of the size distribution of SFTs in gold nanowires proved that the average size distribution of SFT was positively related to the nuclear stopping power of incident ions, i.e., the higher nuclear stopping power of incident ions could generate SFT with a larger average size in gold nanowires.

Structural modification in swift heavy ion irradiated muscovite mica

Two-layer monoclinic (2M) muscovite mica sheets with a thickness of 12 μm are irradiated with Sn ions at room temperature with electronic energy loss (dE/dx)e of 14.7 keV/nm. The ion fluence is varied between 1×1011 and 1×1013 ions/cm2. Structural transition in irradiated mica is investigated by x-ray diffraction (XRD). The main diffraction peaks shift to the high angles, and the inter-planar distance decreases due to swift heavy ion (SHI) irradiation. Dehydration takes place in mica during SHI irradiation and mica with one-layer monoclinic (1M) structure is thought to be generated in 2M mica after SHI irradiation. In addition, micro stress and damage cross section in irradiated mica are analyzed according to XRD data. High resolution transmission electron microscopy (HRTEM) is used on the irradiated mica to obtain the detailed information about the latent tracks and structural modifications directly. The latent track in mica presents an amorphous zone surrounded by strain contrast shell, which is associated with the residual stress in irradiated mica.