(Color online) Chemically induced excitation and transport of energetic electrons over Schottky barrier in planar metal-semiconductor nanostructures (side cross-section). Barrier potential separates electric charge, and nanofilm cathode acts as catalyst for the reaction of oxidation of hydrogen to water. ϕ—Schottky barrier height, —vacuum level, Ec —conduction-band bottom, Ef —Fermi energy, Ev —valence band top. Schematics on the right depict sample mounting without a sample holder, using thin conductive wires attached to electrical feedthroughs of the analytical chamber.
(Color online) Sample front view and electrical circuit schematics. Resistive heating voltage is applied at the Pt nanofilm terminals a-b. RTD temperature sensor is attached in the middle of the nanofilm area. Chemically induced current I and forward bias current I 0 due to the heating voltage are measured in the back contact circuit b-c.
(Color online) Examples of current kinetics and explanation of the current separation procedure. Resistively heated Pt/n-GaP sample of 513 K surface temperature is exposed to H2 + 7O2 (a) and H2 + 7N2 (b) mixtures of 120 T total pressure. For the nanofilm heating voltage on, the forward bias current I 0 is recorded as a constant −10.5 μA instrumental compliance, rather than an actual value. Current generated by the sample is identified upon elimination of the forward bias component by switching off the nanofilm heating voltage. Difference of the peak values recorded in the reactive and neutral mixtures for the same nanocathode temperature is the nonadiabatic chemicurrent component.
(Color online) Top: Variance of the total current magnitude with sample surface temperature; inset plot shows the separated nonadiabatic and thermal components. Bottom: Nonadiabatic current fraction in the total current, , and the surface reaction rate.
(Color online) Dependence of the hot electron (nonadiabatic) and thermal currents on the surface reaction rate. The linear fit (dash line) represents a hot electron yield of 0.02 per H2 molecule oxidized.
Parameters of nanofilm resistive heating in 120 Torr mixture.
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