Hybrid Metal–Semiconductor Nanostructure for Ultrahigh Optical Absorption and Low Electrical Resistance at Optoelectronic Interfaces

Engineered optoelectronic surfaces must control both the flow of light and the flow of electrons at an interface; however, nanostructures for photon and electron management have typically been studied and optimized separately. In this work, we unify these concepts in a new hybrid metal–semiconductor surface that offers both strong light absorption and high electrical conductivity. We use metal-assisted chemical etching to nanostructure the surface of a silicon wafer, creating an array of silicon nanopillars protruding through holes in a gold film. When coated with a silicon nitride anti-reflection layer, we observe broad-band absorption of up to 97% in this structure, which is remarkable considering that metal covers 60% of the top surface. We use optical simulations to show that Mie-like resonances in the nanopillars funnel light around the metal layer and into the substrate, rendering the metal nearly transparent to the incoming light. Our results show that, across a wide parameter space, hybrid metal–semiconductor surfaces with absorption above 90% and sheet resistance below 20 Ω/□ are realizable, suggesting a new paradigm wherein transparent electrodes and photon management textures are designed and fabricated together to create high-performance optoelectronic interfaces

Schottky Barrier Catalysis Mechanism in Metal-Assisted Chemical Etching of Silicon

Metal-assisted chemical etching (MACE) is a versatile anisotropic etch for silicon although its mechanism is not well understood. Here we propose that the Schottky junction formed between metal and silicon plays an essential role on the distribution of holes in silicon injected from hydrogen peroxide. The proposed mechanism can be used to explain the dependence of the etching kinetics on the doping level, doping type, crystallographic surface direction, and etchant solution composition. We used the doping dependence of the reaction to fabricate a novel etch stop for the reaction

Electrochemical Tuning of MoS₂ Nanoparticles on Three-Dimensional Substrate for Efficient Hydrogen Evolution

Molybdenum disulfide (MoS₂) with the two-dimensional layered structure has been widely studied as an advanced catalyst for hydrogen evolution reaction (HER). Intercalating guest species into the van der Waals gaps of MoS₂ has been demonstrated as an effective approach to tune the electronic structure and consequently improve the HER catalytic activity. In this work, by constructing nanostructured MoS₂ particles with largely exposed edge sites on the three-dimensional substrate and subsequently conducting Li electrochemical intercalation and exfoliation processes, an ultrahigh HER performance with 200 mA/cm² cathodic current density at only 200 mV overpotential is achieved. We propose that both the high surface area nanostructure and the 2H semiconducting to 1T metallic phase transition of MoS₂ are responsible for the outstanding catalytic activity. Electrochemical stability test further confirms the long-term operation of the catalyst