Near-Surface $^{125}{\mathrm{Te}}^{+}$ Spins with Millisecond Coherence Lifetime

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Near-Surface ${}^{125}{Te}^{+}$ Spins with Millisecond Coherence Lifetime

Mantas Šimėnas, James O’Sullivan, Oscar W. Kennedy, Sen Lin, Sarah Fearn, Christoph W. Zollitsch, Gavin Dold, Tobias Schmitt, Peter Schüffelgen, Ren-Bao Liu, and John J. L. Morton

Phys. Rev. Lett. 129, 117701 – Published 9 September 2022

Abstract

Impurity spins in crystal matrices are promising components in quantum technologies, particularly if they can maintain their spin properties when close to surfaces and material interfaces. Here, we investigate an attractive candidate for microwave-domain applications, the spins of group-VI ${}^{125}{Te}^{+}$ donors implanted into natural Si at depths as shallow as 20 nm. We show that surface band bending can be used to ionize such near-surface Te to spin-active ${Te}^{+}$ state, and that optical illumination can be used further to control the Te donor charge state. We examine spin activation yield, spin linewidth, and relaxation ( $T_{1}$ ) and coherence times ( $T_{2}$ ) and show how a zero-field 3.5 GHz “clock transition” extends spin coherence times to over 1 ms, which is about an order of magnitude longer than other near-surface spin systems.

Received 24 September 2021
Revised 11 March 2022
Accepted 20 July 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.117701

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Quantum information with solid state qubits Quantum memories Spin coherence

Electron spin resonance Ion implantation Secondary ion mass spectrometry

Condensed Matter, Materials & Applied PhysicsQuantum Information, Science & Technology

Authors & Affiliations

Mantas Šimėnas ¹, James O’Sullivan¹, Oscar W. Kennedy ¹, Sen Lin², Sarah Fearn ³, Christoph W. Zollitsch ¹, Gavin Dold ¹, Tobias Schmitt⁴, Peter Schüffelgen ⁴, Ren-Bao Liu ², and John J. L. Morton ^1,5,*

¹London Centre for Nanotechnology, UCL, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
²Department of Physics, Centre for Quantum Coherence and The Hong Kong Institute of Quantum Information Science and Technology, The Chinese University of Hong Kong, Hong Kong, China
³Department of Materials, Imperial College London, London SW7 2BX, United Kingdom
⁴Institute for Semiconductor Nanoelectronics, Peter Grünberg Institute 9, Forschungszentrum Jülich and RWTH Aachen University, 52425 Jülich, Germany
⁵Department of Electrical and Electronic Engineering, UCL, Malet Place, London WC1E 7JE, United Kingdom

^*Corresponding author. jjl.morton@ucl.ac.uk

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Vol. 129, Iss. 11 — 9 September 2022

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Figure 1
(a) Spin eigenenergies of ${}^{125}{Te}^{+}$ :Si with $S_{x}$ and $S_{z}$ transitions marked in blue and red, respectively. (b) Frequencies of allowed spin transitions, where the line intensity is proportional to the transition probability. Echo-detected spectra obtained at 9.65 GHz are shown in black. (c) First order magnetic field dependence of the transition frequencies. (d),(e) Echo-detected spectra of ${}^{125}{Te}^{+} : Si$ close to zero magnetic field with the cavity oriented to measure (d) $S_{z}$ and (e) $S_{x}$ transitions. Solid lines show simulations assuming only a hyperfine constant of 3.4965 GHz to ${}^{125}{Te}$ nucleus, or, in addition, a superhyperfine (SHF) interaction with a neighboring [110]-shell ${}^{29}{Si}$ nuclear spin. All measurements are taken at 10 K. Circles in (b)–(e) show fields and transitions, where $T_{2}$ measurements are performed.
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Figure 2
(a) Cartoons showing the different ionisation mechanisms of Te in silicon. (b) EDFSs performed at X band for $S_{x}$ transitions. (c)–(e) Simulated band profiles for the three samples used in this study assuming FLP of 0.4 eV below the conduction band. The simulation results are consistent with EDFSs in (b). (c) Intrinsic wafer with 20 keV implant energy gives all Te singly ionized by surface band bending. (d) $p$ -type wafer with 20 keV implant energy has approximately all Te doubly ionized. (e) $p$ -type wafer with 800 keV implant energy has the Fermi level close to the singly ionized Te level as $1 / 10$ of Te atoms are ionized by sacrificing an electron to the boron acceptors present at $1 / 10$ the density of Te.
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Figure 3
Energy levels and electron transitions of Te:Si under illumination of (a) 4300 nm, (b) 2800 nm, and (c) 1050 nm light. The labels of energy levels are marked in (a). Colored vertical lines show the energy of incident photons supplied by LEDs at cryogenic temperatures and indicate which levels are excited by these photons. Vertical arrows show electron capture. Green arrows indicate population swapping between levels under illumination with arrow direction indicating the shift of population of Te donors under illumination. (d) Echo intensity from the shallow-implanted intrinsic sample as a function of time as LEDs are shone at the sample during the echo acquisition (red and blue circles) at 10 K. The inset shows the echo integral as a function of cumulative 2800 nm illumination showing that the echo is suppressed.
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Figure 4
$T_{2}$ as a function of $\partial f / \partial B_{0}$ for (a) $S_{x}$ and (b) $S_{z}$ transitions and different measurement conditions and samples. Points where $T_{2}$ is suppressed by ESEEM are indicated with increased transparency. The solid curves mark the limit to $T_{2}$ considering nuclear spin dynamics as a function of electron spin $\partial f / \partial B_{0}$ . Adding in the effects of classical magnetic field noise gives good agreement to experiment (dashed curves).
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Physical Review Letters

Near-Surface Te+125 Spins with Millisecond Coherence Lifetime

Mantas Šimėnas, James O’Sullivan, Oscar W. Kennedy, Sen Lin, Sarah Fearn, Christoph W. Zollitsch, Gavin Dold, Tobias Schmitt, Peter Schüffelgen, Ren-Bao Liu, and John J. L. Morton

Phys. Rev. Lett. 129, 117701 – Published 9 September 2022

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Near-Surface ${}^{125}{Te}^{+}$ Spins with Millisecond Coherence Lifetime