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Volume 3, Issue 2
ISSN: 2470-9905
Crystallography 2017
October 16-17, 2017
2
nd
International Conference on
October 16-17, 2017 | Chicago, USA
Applied Crystallography
Proton dynamics in ZnO nanorods: An NMR study
Jun Kue Park
Korea Atomic Energy Research Institute, South Korea
T
he rotating-frame spin-lattice relaxation of two types of the hydrogen donors was well distinguished in the 1H nuclear magnetic
resonance (NMR) measurements, providing a unique opportunity to study the distinct proton dynamics in ZnO nanorods. NMR
relaxometry is a powerful technique of atomic-scale access to probe ion hopping motion in solids. The laboratory-frame relaxation
rate is effective for probing nuclear spin processing in radio frequency range, i.e., fast diffusing spins. The rotating-frame relaxation
rate, on the other hand, effectively probes motions occurring at ultralow-frequencies. While spin-lattice relaxation in the laboratory-
frame showed a single-exponential form presumably due to spin mixing by spin diffusion, the spin-lattice relaxation in the rotating-
frame showed a well-resolved double-exponential form, allowing us to distinguish the dynamics of the two distinct proton species in
ZnO synthesized at relatively low-temperature of 573 K. Here, we demonstrate that the conversion from interstitial H (Hi) to oxygen-
substitution H (HO) in ZnO dynamically takes place at elevated temperatures by means of the 1H NMR. The activation barriers for
migration of Hi and for binding of Hi with an oxygen vacancy to form HO are revealed to be 0.27 eV and 0.51 eV, supporting those
obtained by ab initio calculations. In proton-implanted ZnO, we identify comprehensive hydrogen species and investigate their
dynamical properties. Unlike in unirradiated sample, after irradiation mobile protons at the interstitial site were observed in the
systems synthesized at relatively high-temperature of 773 K. The activation energy obtained was 0.46 eV by the Arrhenius relation,
corresponding to that of long-range hopping motion. Multiple NMR lines at ~1 ppm, assigned to the hydroxyl group were observed
and their diffusion properties have been investigated before and after irradiation. Our work gives manifest evidence for the first time
from a microscopic point of view that implanted protons become mobile in the lattice.
jkuepark@kaeri.re.krStruct Chem Crystallogr Commun, 3:2
DOI: 10.21767/2470-9905-C1-003