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The influence of heat treating n -type bulk β -Ga 2 O 3 in hydrogen (H 2) and argon (Ar) gases on the presence of the defect level commonly labeled as E 1 was studied. Fourier transform-infrared spectroscopy confirms that hydrogen (H) is incorporated into β -Ga 2 O 3 during H 2 annealing at 900 °C. Deep-level transient spectroscopy measurements reveal that the concentration of the E 1 level is promoted by the introduction of H, in contrast to what is observed in samples heat-treated in an Ar flow. We further find the E 1 level to be stable against heat treatments at 650 K, both with and without an applied reverse-bias voltage. Potential candidates for the defect origin of E 1 are investigated using hybrid-functional calculations, and three types of defect complexes involving H are found to exhibit charge-state transition levels compatible with E 1 , including substitutional H at one of the threefold coordinated O sites, Ga-substitutional shallow donor impurities passivated by H, and certain configurations of singly hydrogenated Ga–O divacancies. Among these types, only the latter exhibit H binding energies that are consistent with the observed thermal stability of E 1. [ABSTRACT FROM AUTHOR]

The influence of heat treating n -type bulk β -Ga 2 O 3 in hydrogen (H 2) and argon (Ar) gases on the presence of the defect level commonly labeled as E 1 was studied. Fourier transform-infrared spectroscopy confirms that hydrogen (H) is incorporated into β -Ga 2 O 3 during H 2 annealing at 900 °C. Deep-level transient spectroscopy measurements reveal that the concentration of the E 1 level is promoted by the introduction of H, in contrast to what is observed in samples heat-treated in an Ar flow. We further find the E 1 level to be stable against heat treatments at 650 K, both with and without an applied reverse-bias voltage. Potential candidates for the defect origin of E 1 are investigated using hybrid-functional calculations, and three types of defect complexes involving H are found to exhibit charge-state transition levels compatible with E 1 , including substitutional H at one of the threefold coordinated O sites, Ga-substitutional shallow donor impurities passivated by H, and certain configurations of singly hydrogenated Ga–O divacancies. Among these types, only the latter exhibit H binding energies that are consistent with the observed thermal stability of E 1. [ABSTRACT FROM AUTHOR]

We have used a combination of optical absorption and electrical conductivity measurements to study the effect of the main donor on small polarons in rutile TiO2 single crystals rendered n-type conductive by hydrogenation or doping with Nb. The electrical conductivity measured at 295 K for hydrogenated samples shows a clear correlation with the interstitial hydrogen (Hi) concentration, which is consistent with reports that Hi is the main shallow donor in rutile TiO2. Conductive samples exhibit two distinct optical absorption bands in the IR spectral region, at ω1 = 6500 cm−1 (∼0.8 eV) and ω2 = 3100 cm−1 (∼0.4 eV), which are present in both hydrogen-rich and Nb-doped samples. The intensities of the absorption bands are proportional to the electrical conductivity, and they exhibit an Arrhenius-like temperature dependence for temperatures between 25–50 K and 50–100 K for H-doped and Nb-doped samples, respectively. The thermal activation energies (EAs) for the absorption bands depend strongly on the main donor: ω2 exhibits EA(H) and EA(Nb) of ∼4 and ∼10 meV, respectively, whereas ω1 shows EA(H) and EA(Nb) of ∼1 and ∼2 meV, respectively. The combination of temperature-dependent data for the optical absorption bands and interstitial deuterium (Di)-small polaron vibrational lines support a model where the thermal activation is associated with the reconfiguration of small polarons involving Ti sites far away from the donor. The thermal activation of the optical absorption bands gives us insight into the dynamics of donor-dependent small polaron reconfiguration in rutile TiO2. [ABSTRACT FROM AUTHOR]

Diffusion and relaxation was observed in hydrating white cement pastes with differing water contents using nuclear magnetic resonance.