December 1 - 6, 2024
Boston, Massachusetts
Symposium Supporters
2024 MRS Fall Meeting & Exhibit
QT03.02.02

Novel Growth of Phase-Pure α-Sn Quantum Microstructures on Si Using a Ge Seed Layer

When and Where

Dec 2, 2024
2:00pm - 2:15pm
Sheraton, Fifth Floor, The Fens

Presenter(s)

Co-Author(s)

Shangda Li1,Shang Liu1,Jules Gardener2,Austin Akey2,Xiaoxue Gao1,Xiaoxin Wang1,Jifeng Liu1

Dartmouth College1,Harvard University2

Abstract

Shangda Li1,Shang Liu1,Jules Gardener2,Austin Akey2,Xiaoxue Gao1,Xiaoxin Wang1,Jifeng Liu1

Dartmouth College1,Harvard University2
The elemental topological quantum material α-Sn has recently gained significant attention for its unique transport properties and potential spintronics applications [1]. Overcoming the notorious "tin pest" instability, α-Sn with its diamond cubic structure offers promising integration possibilities for topological quantum devices on Si. However, direct growth on Si is challenged by a significant lattice mismatch. Growths of α-Sn on Si were reported, but the thickness was limited to below 10 nm [2].

In this study, we introduce a novel method to grow 200 nm-thick α-Sn microstructures with lateral dimensions reaching 0.4-1 μm on a Si substrate by employing a 2 nm-thick Ge seed layer via physical vapor deposition [3]. Up to 86% of as-deposited β-Sn converts to α-Sn under optimal thermal annealing conditions, which significantly enhances the phase purity compared to ~50% α-Sn in our previous work of Ge-doped α-Sn grown on native oxide on Si [4]. Cooling process is found to be critical to α-Sn formation. Using in situ Raman spectroscopy, we confirm that as-deposited β-Sn melts during rapid thermal annealing (RTA) at 350-450°C and solidifies into α-Sn upon cooling, facilitated by heterogeneous nucleation on the Ge layer. High-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) reveal single-grain α-Sn microdots with identical crystallographic orientation within each microdot. Approximately 1 at.% Ge diffuses into the α-Sn, aiding thermodynamic stabilization and processing. Tuning cooling conditions and employing HCl etching, we further achieve phase-pure α-Sn microstructures suitable for quantum device applications. This α-Sn incorporates a compressive strain of ~-0.59%, induced by the Ge seed layer, confirming its nature as a 3D topological Dirac semimetal compatible with Si-based quantum devices [5]. Our discoveries provide a platform for several potential applications, including exploring point-contact induced superconductivity [6], investigating transport properties [7], and studying optical modulation [8]. Our method’s compatibility with CMOS technology presents a significant advancement toward quantum materials integration on Si and opens up opportunities for practical applications in quantum electronics and spintronics. Future work will explore a broader range of Ge seed layer thicknesses and epitaxial growth of Ge seed layer on Si substrate to further optimize the α-Sn growth process and device integration.

Reference
[1] Si, N. et al. J. Phys. Chem. Lett. 2020, 11, 1317–1329.
[2] Ding, J. et al. Adv. Mater. 2021, 33, 1–9.
[3] Liu, S. et al. Small Methods 2024, 2400550.
[4] Liu, S. et al. Commun. Mater. 2022, 3, 17.
[5] Anh, L. D. et al. Adv. Mater. 2021, 33, 2104645.
[6] Aggarwal, L. et al. Nat. Mater. 2016, 15, 32–37.
[7] Ding, Y. et al. arXiv: 2308.02192 2023.
[8] Li, W. et al. Nano Lett. 2014, 14, 955–959.

Keywords

phase transformation | quantum materials | Sn

Symposium Organizers

Paolo Bondavalli, Thales Research and Technology
Nadya Mason, The University of Chicago
Marco Minissale, CNRS
Pierre Seneor, Unité Mixte de Physique & Univ. Paris-Saclay

Session Chairs

Henri Jaffres
Pierre Seneor

In this Session