| AVS 60th International Symposium and Exhibition | |
| Helium Ion Microscopy Focus Topic | Thursday Sessions |
| Session HI-ThA |
| Session: | Imaging and Lithography with Helium Ions |
| Presenter: | V. Shutthanandan, Pacific Northwest National Laboratory |
| Authors: | V. Shutthanandan, Pacific Northwest National Laboratory S. Manamdhar, Pacific Northwest National Laboratory M.I. Nandasiri, Pacific Northwest National Laboratory A. Devaraj, Pacific Northwest National Laboratory D.E. Perea, Pacific Northwest National Laboratory S.A. Thevuthasan, Pacific Northwest National Laboratory D.M. Asner, Pacific Northwest National Laboratory D. Rubin, Cornell University W.H. Hartung, Cornell University Y. Li, Cornell University |
| Correspondent: | Click to Email |
The performance of future high intensity positron and proton accelerators is likely affected by the electron cloud (EC) generated by the secondary electrons yield (SEY) created from the inner wall of vacuum chambers. One of the promising techniques for suppressing EC formation in regions with magnetic fields is the use of modified surfaces such as longitudinally grooved chamber surfaces to help suppress the escape of secondary electrons from the walls into the central volume of the vacuum chamber. However, the use of macroscopic structures in chambers increases the vacuum chamber impedance and can adversely impact a high intensity beam, particularly if the beam motion has a significant component perpendicular to the direction of the structures. A possible way to obtain the same “geometric” suppression of the electron cloud with less impact on the particle accelerator beams of interest is to prepare the vacuum chamber surfaces with microstructures produced by ion bombardment. In this project we have investigated the secondary electron yield from the ion beam modified Cu and Al surfaces, which are typically employed in high energy positron/electron circular accelerators, and correlate the yield to the chemical and structural properties of the microstructures generated by the high energy ion beam and their interfaces. “Ridge” like structures were generated by irradiating the surfaces using 1 MeV gold, copper and aluminum ions at 60 degrees or more from the normal to the surface. Modified sample surfaces were investigated using Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy imaging (XPS), Helium ion microscopy (HIM), Atomic Force Microscopy (AFM), high-resolution transmission electron microscopy (HRTEM) and Atom probe tomography (APT). HIM micrographs obtained from the as implanted samples show that the surface of the implanted region underwent substantial rearrangement and formed “ridge” like structures at higher ion fluence. These “ridge” like structures are formed throughout the implanted region with an average height of 1 to 2 microns. The measured secondary electron yield from these structures will be correlated to the microstructures and the combined results will be presented.