title: Parallel Aligned Mesopore Arrays in Pyramidal-Shaped Gallium Nitride and Their Photocatalytic Applications.
abstract: 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.
authors.affiliation: School of Materials Science and Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.
authors.forename: Hee Jun
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: School of Materials Science and Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.
authors.forename: Joonmo
authors.initials: J
authors.lastname: Park
authors.affiliation: School of Materials Science and Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.
authors.forename: Byeong Uk
authors.initials: BU
authors.lastname: Ye
authors.affiliation: Department of Materials Science and Engineering Division of Advanced Materials Science, Pohang University of Science and Technology , San 31 Hyoja-Dong, Pohang 790-784, Republic of Korea.
authors.forename: Chul Jong
authors.initials: CJ
authors.lastname: Yoo
authors.affiliation: Department of Materials Science and Engineering Division of Advanced Materials Science, Pohang University of Science and Technology , San 31 Hyoja-Dong, Pohang 790-784, Republic of Korea.
authors.forename: Jong-Lam
authors.initials: JL
authors.lastname: Lee
authors.affiliation: Department of Physics, Chonnam National University , Gwangju 500-757, Republic of Korea.
authors.forename: Sang-Wan
authors.initials: SW
authors.lastname: Ryu
authors.affiliation: Department of Materials Science and Engineering, Korea University , Anam-dong 5-ga, Seongbuk-gu, Seoul 136-713, Republic of Korea.
authors.forename: Heon
authors.initials: H
authors.lastname: Lee
authors.affiliation: School of Materials Science and Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.
authors.forename: Kyoung Jin
authors.initials: KJ
authors.lastname: Choi
authors.affiliation: School of Materials Science and Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.
authors.forename: Jeong Min
authors.initials: JM
authors.lastname: Baik
keywords: electrochemical etching; nanosphere-assisted lithography; parallel aligned mesopore arrays; photocatalytic water-splitting; pyramidal-shaped GaN