NQCP Seminar - Prof. Dr. Jordi Arbiol, Catalan Institute of Nanoscience and Nanotechnology

Quantum nanostructures at atomic scale: From vertical hybrid nanowires to planar nanowire networks and 2DEG/2DHG systems 

Hybrid superconductor/semiconductor-based quantum devices (e.g.: for quantum computing applications) are mainly based on 3 different technologies: vapour-liquid-solid (VLS) grown vertical nanowires, selected area growth (SAG) nanowire networks and 2-dimensional electron gases (2DEG). 

First of all, by using atomic-scale aberration corrected Scanning Transmission Electron Microscopy (AC STEM) and 3D modelling, we will study the influence of polarity on the development and properties of these complex NW-like hybrid heterostructures vertically grown by VLS.[1-3]

In a second part, we will show the natural evolution of this vertical technology to the flat growth of NW networks on III-V substrates. Developing growth techniques towards horizontally assembled semiconductor nanowire networks base on SAG is essential to promote their integration into large-scale functional circuit platforms and devices for electronic, photonic and quantum applications and more over to address a high scalability. In these complex core@shell or confined multilayer nanostructure configurations, strain relaxation mechanisms during the epitaxial growth play a key role in determining their final morphology, crystal structure and physical properties. To analyze these mechanisms, in the present work, atomic-scale Cs-corrected Scanning Transmission Electron Microscopy studies are performed on horizontal arrays of nanowires.  Core morphology-dependent strain fields, involving plane bending and the resulting formation of low angle polar boundaries, are observed. The origin of this phenomenon and its consequences on the electronic band structure are discussed. Monochromated Valence Electron Energy Loss Spectroscopy is employed to spatially map the heterostructure’s bandgap with sub-nanometer resolution and certify the influence of the high mismatch induced strain on the topological electronic properties at the interface of the core-shell region. These findings highlight the importance and potential of accurate sub-nanometer-level understanding of the structure-property relations in the novel SAG and guided growth mechanisms of heterostructured semiconductor nanowire networks.[4-6]

Finally, we will address the newly developed 2DEG heterostructures based on SiGe, fully compatible with CMOS technology, were the strain and composition at the Ge quantum wells will determine their final quantum properties [7-8].

[1] M. de la Mata, et al., Nano Letters, 19, 3396 (2019)

[2] M. Zamani, et al., Advanced Materials, 32, 2001030 (2020)

[3] M. Valentini, et al., Nature, 612, 442 (2022)

[4] E. Oksenberg, et al., ACS Nano, 11, 6155 (2017)

[5] M. Friedl, et al., Nano Letters, 18, 2666 (2018)

[6] S. Martí-Sánchez, M. Botifoll, et al., Nature Commun., 13, 4089 (2022)

[7] D. Jirovec, et al., Nature Materials, 20, 1106 (2021)

[8] B. Paquelet Wuetz, et al., Nature Commun., 14, 1385 (2023)