Identifying Implantation Damage and Spin Qubits in Three-Dimensions Using Multislice Electron Ptychography

Solid-state spin defects are promising platform for realizing quantum bits (qubits) [1]. Ion implantation is an instrumental method for creating and manipulating these spin qubits. The accelerated ion beam used in implantation transfers most of its kinetic energy to the host matrix via collisions that displace host atoms and/or create vacancies [2]. Subsequent annealing is followed to repair the damage and electrically activate the dopants [3]. However, this process can lead to unpredicted results, such as unknown defect-related photoluminescence peaks, potentially due to the interactions with preexisting implantation damage [4]. Moreover, isolating spin qubits is necessary to minimize decoherence [5]. In this context, it highlights the necessity of directly studying the consequences of ion implantation, including implantation damage and dopant identification.<br/><br/>Conventional high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging has been employed to identify atomic defects, particularly heavy transition metal dopants, owing to Z-contrast. Moreover, through-focus HAADF imaging enables 3D information. However, it has limitations on sample (around/less than 10 nm) and cannot separate the surface damage contrast [6]. In addition, the z-contrast of HAADF has very low sensitivity for light elements, which results in missing their structural information. These limitations challenge the accurate interpretation of the structures, thereby limiting their reliability in providing precise insights into the local environments in the vicinity of point defects.<br/><br/>To address these limitations, we introduce multislice electron ptychography, offering several advantages including enhanced spatial and depth resolution by accounting for dynamical scattering [7]. In this presentation, using Er-implanted 4H-SiC (unannealed) as a model system, we demonstrate that multislice electron ptychography can quantify the consequences of ion implantation in three dimensions at previously inaccessible concentration levels with conventional electron microscopy. Analyzing ptychographic datasets at various depths reveals atomic displacements as a function of ion implantation depth, highlighting significant damage near the implantation surface. Forward modeling and electron scattering simulations help calibrate these displacements on peak phase, ensuring accurate detection of both dopants and vacancies. Additionally, we elucidate the local structure surrounding atomic defects, showing significant lattice distortion around Si vacancy. This work enhances our understanding of implantation damage and provides a framework for investigating spin defects and their local structures. Furthermore, these findings can support the development of simulations, such as Monte Carlo and molecular dynamics, leading to more accurate predictions of the consequences of implantation and helping to achieve better-optimized implantation parameters.<br/><br/>1. G. Wolfowicz <i>et al.</i> Nature Reviews Materials <b>6</b> (2021), p. 906-925.<br/>2. A. Gentils <i>et al.</i>, Journal of Materials Science<i> </i><b>46</b> (2011), p. 6390-6395.<br/>3. Y. Zhang <i>et al. </i>Nature Communications <b>6</b> (2015), 8049.<br/>4. T. Kobayashi <i>et al. </i>Journal of Physics D: Applied Physics <b>55 </b>(2021), 105303.<br/>5. D. Chirstle <i>et al.</i> Nature Materials <b>14</b> (2015), p.160-163.<br/>6. G. Satio <i>et al.</i> Ultramicroscopy <b>175</b> (2017), p. 97-104.<br/>7. Z. Chen <i>et al. </i>Science <b>372</b> (2021), p. 826-831.<br/>8. The authors acknowledge funding from AFOSR (FA9550-22-1-0370). This work was carried out in part using the facilities at MIT.nano.