Controlled Formation of Sn-Li Donor in ZnO for Quantum Applications

Donor in ZnO are promising solid-state spin qubits with an efficient spin-photon interface through the donor bound exciton. The long electron spin population relaxation time approaches a second, showing the potential for a long spin coherence time in purified ZnO[1]. Furthur, indium donor qubits formed by implantation and annealing demonstrate properties on par with in-grown indium donors[2]. As the donor atomic number increases, the binding energy of the donor increases as well as the hyperfine interaction of the donor electron with the donor nucleus. Al, Ga, and In exhibit hyperfine interactions of 1.45 MHz[3], 12-18 MHz[4], and 100 MHz[5]. It is thus attractive to move to even larger binding energies which could enable direct optical access to the nuclear spin memory.

The chemical identity of the donor-bound exciton line I₁₀ in ZnO remains elusive. Evidence suggests that I₁₀ originates from a double-donor-acceptor complex Sn_Zn-Li_Zn acting as a single donor [6-7]. Here we have formed I₁₀ through implantation of Sn into Li-rich ZnO substrates, as well as Sn and Li implantation into low-Li ZnO substrates, and observed the appearance and increase of I₁₀ line as implantation fluence increases. The donor identity has been verified with magneto-PL. We will present these findings as well as a second study in which ¹¹⁹Sn is implanted which will enable the determination of a lower bound of the hyperfine interaction of the I₁₀ donor.

This material is based upon work supported by the Air Force Office of Scientific Research under award number FA9550-23-1-0418.

[1] V. Niaouris, M. V. Durnev, X. Linpeng, M. L. K. Viitaniemi, C. Zimmermann, A. Vishnuradhan, Y. Kozuka, M. Kawasaki, and K-M. C. Fu, “Ensemble spin relaxation of shallow donor qubits in ZnO,” Phys. Rev. B 105, 195202 (2022).
[2] X. Wang, C. Zimmermann, M. Titze, V. Niaouris, E. R. Hansen, S. H. D’Ambrosia, L. Vines, E. S. Bielejec, and K-M. C. Fu, “Properties of donor qubits in ZnO formed by indium-ion implantation,” Phys. Rev. Appl. 19, 054090 (2023).
[3] S. B. Orlinskii, J.Schmidt, P. G. Baranov, V. Lorrmann, I. Riedel, D. Rauh, and V. Dyakonov, “Identification of shallow Al donors in Al-doped ZnO nanocrystals: EPR and ENDOR spectroscopy,” Phys. Rev. B 77, 115334 (2008)
[4] C. Gonzalez, D. Block, R.T. Cox, A. Herve, “Magnetic resonance studies of shallow donors in zinc oxide”, J. Cryst. Growth 59, 357 (1982)
[5]D. Block, A. Hervé, and R. T. Cox, “Optically detected magnetic resonance and optically detected ENDOR of shallow indium donors in ZnO,” Phys. Rev. B 25, 6049-6052 (1982)
[6] J. Cullen, D. Byrne, K. Johnston, E. McGlynn, and M. O. Henry, “Chemical identification of luminescence due to Sn and Sb in ZnO,” Applied Physics Letters 102, 192110 (2013).
[7] E. Senthil Kumar, F. Mohammadbeigi, L.A. Boatner, and S.P. Watkins, “High-resolution photoluminescence spectroscopy of sn-doped zno single crystals,” Journal of Luminescence 176, 47–51 (2016).