Morphological changes in Ge surfaces induced by step ion beam irradiation

Porous structures develop on Ge surfaces under ion beam irradiation, owing to the self-organization of point defects. Porous structures have been explored for applications in electronic devices as electrode materials in lithium-ion batteries and as functional components in gas sensors. For these applications, precise control of the porous morphology is crucial to maximize the desired functionality and device performance. The size and morphology of such structures are influenced by various factors, including irradiation fluence, ion energy, and irradiation angle. We investigated the formation of porous structures on Ge surfaces under step irradiation conditions by systematically varying the irradiation parameters. Two-step irradiation is a process in which the irradiation conditions are modified between step 1 and step 2. At 0°angle of incidence, the number of step irradiations only had a minimal effect on the structure formation. However, at varying irradiation angles, the resulting structures were influenced by the step irradiation angle. Under angle-step irradiation with an increased fluence, structures with a combination of the effects of both irradiations were formed. These results demonstrate that step irradiation offers a practical route to finely tailor porous Ge morphologies, thereby enabling performance optimization for applications.