Electronic Structure Of Interstitial Hydrogen In In-Ga-Zn-O Semiconductor Simulated By Muon

We report on the local electronic structure of an interstitial muon (Mu) as pseudohydrogen in In-Ga-Zn oxide (IGZO) semiconductors studied by muon spin rotation/relaxation (mu SR) experiment. In polycrystalline (c-) IGZO, it is inferred that Mu is in a diamagnetic state, where the mu SR time spectra under zero external field are perfectly described by the Gaussian Kubo-Toyabe relaxation function with the linewidth Delta serving as a sensitive measure for the random local fields from In/Ga nuclear magnetic moments. The magnitude of Delta combined with the density functional theory calculations for H (to mimic Mu) suggests that Mu occupies Zn-O bond-center site (Mu(BC)) similar to the case in crystalline ZnO. This implies that the diamagnetic state in c-IGZO corresponds to MuBC+, thus serving as an electron donor. In amorphous (a-) IGZO, the local Mu structure in the as-deposited films is nearly identical to that in c-IGZO, suggesting MuBC+ for the electronic state. In contrast, the diamagnetic signal in heavily hydrogenated a-IGZO films exhibits the Lorentzian Kubo-Toyabe relaxation, implying that Mu accompanies more inhomogeneous distribution of the neighboring nuclear spins that may involve a Mu(-) H--complex state in an oxygen vacancy.