Parallel aligned mesopore arrays in pyramidal-shaped GaN are fabricated by using an electrochemical anodic etching technique, followed by inductively coupled plasma etching assisted by SiO2 nanosphere lithography, and used as a promising photoelectrode for solar water oxidation. The parallel alignment of the pores of several tens of micrometers scale in length is achieved by the low applied voltage and prepattern guided anodization. The dry etching of single-layer SiO2 nanosphere-coated GaN produces a pyramidal shape of the GaN, making the pores open at both sides and shortening the escape path of evolved gas bubbles produced inside pores during the water oxidation. The absorption spectra show that the light absorption in the UV range is ∼93% and that there is a red shift in the absorption edge by 30 nm, compared with the flat GaN. It also shows a remarkable enhancement in the photocurrent density by 5.3 times, compared with flat GaN. Further enhancement (∼40%) by the deposition of Ni was observed due to the generation of an electric field, which increases the charge separation ratio.
Bibliographical noteFunding Information:
This work was financially supported by the Pioneer Research Center Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT, & Future Planning (NRF-2013M3C1A3063602), by the KIST-UNIST partnership program (1.150091.01/2V04450), and by the 2016 Research Fund (1.160034.01) of UNIST (Ulsan National Institute of Science and Technology).
- electrochemical etching
- nanosphere-assisted lithography
- parallel aligned mesopore arrays
- photocatalytic water-splitting
- pyramidal-shaped GaN
ASJC Scopus subject areas
- General Materials Science