Ⅲ-1. Atomic & Solid State Physics (Ion)

RIKEN Accel. Prog. Rep. 56 (2023)
RIKEN
Accel. Prog. Rep. 56 (2023)

Lattice sites of 23 Ne implanted in single-crystal ZnO studied by
β-NMR/NQR spectroscopy
H. Yamazaki,∗1 H. Nishibata,∗2 A. Gladkov,∗1 T. Kawaguchi,∗3 H. Ueno,∗1 Y. Ichikawa,∗2 A. Takamine,∗1T. Sato,∗1 K. Kawata,∗1,∗4 W. Kobayashi,∗3 M. Sanjo,∗3 L. C. Tao,∗5 Y. Nakamura,∗3 T. Asakawa,∗3 Y. Sasaki,∗3K. Totsuka,∗3 K. Doi,∗3 T. Yada,∗3 K. Asahi,∗1 Y. Ishibashi,∗6 K. Imamura,∗1 T. Fujita,∗7 G. Georgiev,∗8 andJ. M. Daugas∗9Zinc oxide is a II-VI binary compound that crystalizes in a hexagonal wurtzite structure. The compoundhas received signiﬁcant attention because of its potential
for application in optoelectronic devices and transparent conducting ﬁlms as well as in space environments
owing to its radiation hardness. In particular, owing towide and direct band gap of 3.4 eV at room temperature,
ZnO can be utilized in next-generation devices for shortwavelength optoelectronics such as light-emitting diodes
operating in the spectral range from blue to ultraviolet.
For utilizing ZnO as semiconductors, both n-type and ptype doped ZnO are necessary. We can fabricate n-type
ZnO through the partial substitution of Zn with Al, Ga,or In, whereas fabricating a reliable high-quality p-type
ZnO still remains a challenge. Despite considerable research conducted so far, high-quality p-type ZnO has notbeen fabricated.
Recently, ﬁrst-principles calculations performed by
Malyi et al. indicated that a noble gas (He, Ne, or Ar)
implanted in ZnO can serve as a new type of dopant.1)
In spite of its fully occupied atomic orbitals, the noble
gas strongly changes the surrounding electronic statesby pushing away the electrons around it. This suggeststhat a noble gas can be a functional dopant in ZnO, andthe investigation of ZnO using noble-gas nuclei as local
probes is much anticipated. In this study, we investigate,in particular, Ne implantation into single-crystal ZnO.
For details of the experimental setup, see our earlier
report.2) First, using the β-NMR method, we determined
the nuclear g-factor for the radioactive 23 Ne isotope (nuclear spin I = 5/2) that decays through β-emission into
the nucleus 23 Na with a half-life of T1/2 = 37 s. Thereafter, we implanted the 23 Ne isotopes as probe nuclei
in ZnO and measured the electric ﬁeld gradient (EFG)at the 23 Ne stopping sites using β-NQR method. EFGs
are highly sensitive to the electronic density in the vicinity of the relevant nucleus. This sensitivity can be used
to identify the crystallographic sites for the implanted
23Ne and to study the eﬀect of 23 Ne implantation onthe charge distribution around the nucleus. The β-NQRspectrum obtained at 47 K is depicted in Fig. 1.
We determined the electric ﬁeld gradient Vzz at the∗1
∗2
∗3
∗4
∗5

∗6
∗7
∗8
∗9RIKEN Nishina Center
Department of Physics, Kyushu University
Department of Physics, Hosei University
Center for Nuclear Study, University of Tokyo
School of Physics, Peking University
Cyclotron and Radioisotope Center, Tohoku University
Department of Physics, Osaka University
CSNSM, CNRS/IN2P3, Université Paris-Sud
CEA/DAM-Ile de FranceFig. 1. β-NQR spectrum of 23 Ne implanted in ZnO single
crystal. The dashed line represents the least χ-square
ﬁtting result to a Gaussian function.

position of 23 Ne in ZnO. The value of (3.1 ± 0.3) ×1020 [V/m2 ] for 23 Ne compare well with that for 20 Naon the interstitial site (see Table 1). Although Ne occupies an octahedral interstitial site (the lowest energysite for Ne),1) Na in the form of ion (Na+ ) is shifted by0.23 Å from the ideal octahedral site parallel to the caxis.6) Considering that both Ne and Na+ have the same
electron conﬁguration 1s2 2s2 2p6 , we must study the position dependence of Vzz further in detail theoretically.
Table 1. Experimental results of the electric ﬁeld gradientVzz in ZnO for the β-NQR probes of 8 Li, 12 N, and 20 Na.

Implanted
probeVzz[1020 V/m2]
Lattice site

8Li 3)

1.342±0.001
interstitial site
close tooctahedral site
0.6029±0.0004
Zn
substitutionalsite12N 4)

0.86
±0.11
siteunclear20Na 5)

2.7
interstitialsite close tooctahedralsite6)
1.8Zn
substitutionalsite6)

References
1) O. I. Malyi et al., npj Comput. Mater. 5, 38 (2019).
2) H. Nishibata et al., RIKEN Accel. Prog. Rep. 52, 56(2018).
3) J. R. Adelman et al., Phys. Rev. B 106, 035205 (2022).
4) R. Matsumiya et al., Hyperﬁne Interact. 178, 63 (2007).
5) K. Minamisono et al., Nucl. Instrum. Methods Phys. Res.
A 616, 45 (2010).
6) U. Wahl et al., Semicond. Sci. Technol. 31, 095005 (2016).

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