Study of damage generation induced by focused helium ion beam in silicon

Helium ion microscope (HIM) has presented an outstanding ability to image and nanofabricate thin film and two-dimensional materials with high precision. However, the concomitant damage and implantation induced by focused helium ion beam should influence the imaging quality and nanomachining efficiency inevitably, especially for bulk samples. In this work, the authors investigated the generation process of damages at nanoscales in single crystalline bulk silicon caused by ions implantation in HIM using transmission electron microscopy. The dependence of implantation and damage on ion dose, ion energy, and beam current was also discussed and analyzed. It was found that the damage should be originated from the local defects caused by ion implantation and the crystal structure could be gradually destroyed and transform into amorphous silicon with the generation and growth of subsurface nanobubbles as ion dose increased. The local concentration of implanted helium ion was found as a universal factor to impact on the damage level and the size of nanobubbles directly. These findings not only shed lights on the effective imaging and nanofabrication of HIM but also provide a further understanding in the nuclear irradiation area. Published by the AVS.