RESUMEN
Gallium arsenide (GaAs) provides a suitable bandgap (1.43 eV) for solar spectrum absorption and allows a larger photovoltage compared to silicon, suggesting great potential as a photoanode toward water splitting. Photocorrosion under water oxidation condition, however, leads to decomposition or the formation of an insulating oxide layer, which limits the photoelectrochemical performance and stability of GaAs. In this work, a self-limiting electrodeposition method of Ni on GaAs is reported to either generate ultra-thin continuous film or nanoislands with high particle density by controlling deposition time. The self-limiting growth mechanism is validated by potential transients, X-ray photoelectron spectroscopy composition and depth profile measurements. This deposition method exhibits a rapid nucleation, forms an initial metallic layer followed by a hydroxide/oxyhydroxide nanofilm on the GaAs surface and is independent of layer thickness versus deposition time when coalescence is reached. A photocurrent up to 8.9 mA cm-2 with a photovoltage of 0.11 V is obtained for continuous ultrathin films, while a photocurrent density of 9.2 mA cm-2 with a photovoltage of 0.50 V is reached for the discontinuous nanoislands layers in an aqueous solution containing the reversible redox couple K3 Fe(CN)6 /K4 Fe(CN)6 .
RESUMEN
Enormous advancement has been achieved in the field of one-dimensional (1D) semiconductor light-emitting devices (LEDs), however, LEDs based on 1D CdS nanostructures have been rarely reported. The fabrication of CdS@SiO2 core-shell nanorod array LEDs based on a Au-SiO2 -CdS metal-insulator-semiconductor (MIS) structure is presented. The MIS LEDs exhibit strong yellow emission with a low threshold voltage of 2.7 V. Electroluminescence with a broad emission ranging from 450 nm to 800 nm and a shoulder peak at 700 nm is observed, which is related to the defects and surface states of the CdS nanorods. The influence of the SiO2 shell thickness on the electroluminescence intensity is systematically investigated. The devices have a high light-emitting spatial resolution of 1.5 µm and maintain an excellent emission property even after shelving at room temperature for at least three months. Moreover, the fabrication process is simple and cost effective and the MIS device could be fabricated on a flexible substrate, which holds great potential for application as a flexible light source. This prototype is expected to open up a new route towards the development of large-scale light-emitting devices with excellent attributes, such as high resolution, low cost, and good stability.