Seminar at the Accelerator – Gregor Hlawacek (HZR)

Speaker: Gregor Hlawacek (HZR)

Title: Focused Ion Beams for spatially resolved materials properties tuning

Abstract: In ion beam processing of materials, spatial control is typically achieved using masks. While this approach is ideally suited for large-scale fabrication of established and well-tested device architectures, it is less appropriate for the rapid development of new concepts. This limitation is mainly related to the relatively slow and costly fabrication of suitable masks, which requires cleanroom
processing and specialized equipment.

Helium Ion Microscopy (HIM) [1] and other Focused Ion Beam (FIB) methods [2] offer unique capabilities for spatially resolved tuning of material properties. FIBs provide access to a wide range of ion species for implantation and defect engineering, and the achievable fluence range extends from single-ion implantation events up to 1 × 1020 ion cm−2.

Here, I will briefly outline the fundamental principles of HIM and liquid-metal-alloy–ion-source (LMAIS) based FIBs, followed by selected examples of defect engineering developed in my group. These include low-fluence applications such as the creation of single-photon emitters in silicon by implanting single or few ions using LMAIS-based FIBs [3]. Further semiconductor applications include the fabrication of single-electron transistor (SET) devices via ion-beam mixing of Si into SiO2 [4]. For both cases, I will discuss how the inherently serial FIB process can be transformed into a large-batch broad-beam approach. Additional examples will highlight the spatially controlled modification of magnetic properties and the fabrication of arbitrarily shaped nanomagnets [5, 6].

References
[1] Hlawacek, G. & Gölzhäuser, A. (eds.) Helium Ion Microscopy. NanoScience and Technology (Springer International Publishing, Switzerland, 2016).
[2] Höflich, K. et al. Roadmap for focused ion beam technologies. Applied Physics Reviews 10, 041311 (2023).
[3] Hollenbach, M. et al. Wafer-scale nanofabrication of telecom single-photon emitters in silicon. Nature Communications 13 (2022).
[4] Xu, X. et al. Site-controled formation of single Si nanocrystals in a buried SiO2 matrix using ion beam mixing. Beilstein Journal of Nanotechnology 9, 2883–2892 (2018).
[5] Nord, M. et al. Strain anisotropy and magnetic domains in embedded nanomagnets. Small 1904738 (2019).
[6] Röder, F. et al. Direct Depth- and Lateral- Imaging of Nanoscale Magnets Generated by Ion Impact. Scientific Reports 5, 16786 (2015).