Electronic structure of interstitial hydrogen in In-Ga-Zn-O semiconductor simulated by muon

• Published in: Applied physics letters 2019-09, Vol.115 (12)
• Main Authors: Kojima, K. M., Hiraishi, M., Okabe, H., Koda, A., Kadono, R., Ide, K., Matsuishi, S., Kumomi, H., Kamiya, T., Hosono, H.
• Format: Article
• Language: English
• Subjects: Applied physics; Density functional theory; Diamagnetism; Electron states; Electronic structure; Hydrogen storage; Indium gallium zinc oxide; Magnetic moments; Muon spin relaxation; Muon spin rotation; Muons; Zinc oxide
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5117771

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 (μSR) experiment. In polycrystalline (c-) IGZO, it is inferred that Mu is in a diamagnetic state, where the μSR time spectra under zero external field are perfectly described by the Gaussian Kubo-Toyabe relaxation function with the linewidth Δ serving as a sensitive measure for the random local fields from In/Ga nuclear magnetic moments. The magnitude of Δ combined with the density functional theory calculations for H (to mimic Mu) suggests that Mu occupies Zn-O bond-center site (MuBC) similar to the case in crystalline ZnO. This implies that the diamagnetic state in c-IGZO corresponds to Mu BC +, 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 Mu BC + 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.