Abstract
Physical properties found in H-related materials such as high-temperature superconductivity have been studied intensively [1]. Hydrogen ion implantation at low temperature, where the thermal H2 desorption is suppressed, is a promising method to realize H-rich materials [2]. Experimental and theoretical structure analyses are important to understand and explore fascinating properties of hydrides. Channeling NRA is an ion beam analysis that can determine the lattice location of H in crystals. In this study, we fabricated PtHx by the H ion implantation at low temperature and investigated its structure by Channeling NRA and DFT calculations.
The sample we used is Pt(100) single crystal. H absorption by the H ion implantation at low temperature was observed near the surface in nuclear reaction analysis (NRA). We performed the Channeling NRA around the surface normal direction using 15N2+ beam with an energy of 6.45 MeV. As shown in Fig. 1(a), decrease or increase in NRA yield at the <100> axis channeling is expected for the H atoms in octahedral (O) or tetrahedral (T) site, respectively. Figure 1(b) shows incident angle dependence of the NRA and RBS yields simultaneously obtained around the <100> axis. The change in the NRA yield was small, indicating that the H atoms are randomly distributed in the crystal. To theoretically investigate the H location, we calculated the site energies of O and T sites in Pt by DFT calculations. Neglecting the zero-point energy, the energies of the two sites coincide within ~50 meV. These results showed that the implanted H atoms occupy both O and T sites in PtHx formed at low temperature. We will also discuss the H dynamics in Pt.
[1] A. P. Drozdov et al., Nature 525 (2015) 73.
[2] Y. Yamashita et al., Phys. Rev. B 104 (2021) L041111.
