The humidity-voltaic effect, i.e. generation of open-circuit voltage (Voc), in Au–porous silicon (PS) interface in humid atmosphere (up to 450 mV at 95% relative humidity) in dark and daylight illumination is discovered. The humidity-stimulated voltage generation is attributed to the splitting of water and hydrogen molecules on the surfaces of the Au catalyst, where further diffusion penetration of hydrogen ions into the Au–PS interface results in the formation of dipoles, thus inducing Voc across dipoles. The generation of Voc (up to 550 mV) has also been observed on dipping of Au–PS structures in different hydrogen-containing solutions (ethanol, benzine, sodium tetraborate pentahydrate, etc). Data of response time-dependent changes of the open-circuit voltage generated in Au–PS structures under humid conditions were used for the estimation of diffusion coefficients of hydrogen. The temperature dependence of the diffusion coefficient of hydrogen at 323–353 K via the pore surfaces of PS is attributed to be D = 1.3 × 10−2exp (−0.25/kT).
The effect of ambient humidity on the current–voltage characteristics of Cu–PS (porous silicon) structures was investigated. The humidity-voltaic effect, i.e. generation of humid voltage (Voc) in Cu–PS interface in humid atmosphere (up to 300 mV at 95% relative humidity) in dark and day-light illumination is discovered. Humidity-stimulated voltage generation is caused by the hydrogen component of water vapour of ambient. A possible mechanism of hydrogen-stimulated voltage generation in Cu–PS interface is suggested. Besides the effect of annealing in the range of 60–200°C in air on Voc of Cu–PS structures was studied and decrease of values of Voc depending on duration of annealing was discovered. These changes were attributed to diffusion of oxygen from air and oxidation of the copper film. (Voc−t) data were used for estimation of the diffusion coefficients of oxygen in the Cu film. The temperature dependence of the oxygen diffusion coefficient in Cu films is described by the relation D = 5.2×10−7exp(−0.44/kT).
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