Humidity-voltaic characteristics of Au–porous silicon interfaces

Abstract

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).

Nanocrystalline Porous Silicon

“…But the discovery of room-temperature photo-and electroluminescence by L. Canham in 1990 boosted the research on porous silicon because of the huge potential in silicon-based integrated sensing and photonic devices (Canham, 1990(Canham, , 1997b(Canham, , 1997c(Canham, ,1997dCanham et al,1991). Also there is a number of publications with the physical and chemical properties, and different applications of PS such as solar cells (Menna, 1997;Aroutiounian , 2004) integrated light-emitting devices on silicon chips (Bondarenko et al, 1997a(Bondarenko et al, , 1997bNakajima et al 2004), selective chemical, gas and humidity sensors (Sailor, 1997), pressure sensors (Pramanik et al, 2005), bio-sensors based on functionalized PS substrates (Dzhafarov et al 2004;DeLouise, 2004), electrolyte-insulator-semiconductor capacitor (EISCAP) based on silicon and PS for detecting different organic materials. Another important characteristic of PS is the ability to tailor the material morphology for the desired applications.…”

Nano-Porous Silicon-Based Mini Hydrogen Fuel Cells

“…It is shown that NaBO 2 byproduct of reaction (20) can be recycle back to NaBH 4 using coke or membrane (Kojima & Haga, 2003). The effect, similar to humidity-voltaic effect (Dzhafarov et al, 2004), i.e. the generation a voltage between the contacts to Au film and Si under humidity exposition, was also discovered on dipping of Au/PS/Si structure into NaBH 4 solution .…”

“…The Au/PS/Si structures were fabricated by the evaporation of a thin Au film onto the PS surface with a porosity of 65% at room temperature by using the electronbeam technique (Dzhafarov et al, 2004). The thickness of the deposited Au film was 150 nm, as obtained by measurements during the evaporation using a deposition controller (Inficon, Leybold).…”

“…The effect of the voltage generation was discovered upon dipping the Au(Ag,Cu)/PS/Si structures into different hydrogen-containing solutions (KOH (potassium hydroxide), CH 3 CH 2 OH (ethanol), CH 3 OH (methanol), C 6 H 12 O 6 (glucose), H 3 BO 3 (boric acid), C 5 H 12 -C 16 H 34 (benzine), NaBH 4 (sodium borohydride), Black sea-water etc.) (Dzhafarov et al, 2004). Hydrogen as a source of clean energy has a number of attractive advantages, such as high energy density, nontoxic reaction products and abundant natural resources.…”

“…On this view, it would be desirable to develop an inorganic proton conducting membrane for fuel cell with technology compatible with standard micro-fabrication techniques. In order to get over the abovementioned disadvantages, we proposed to fabricate novel Schottky-type fuel cell for micro power generation, based on nano (micro)-porous silicon, operating at room temperature under direct exposition of hydrogen-containing gas and liquid compounds Dzhafarov et al, 2002Dzhafarov et al, , 2004Dzhafarov et al, , 2005Dzhafarov et al, , 2011. Fabrication of porous silicon is compatible with micro-fabrication technology.…”