title: Hierarchical ZnO nanorods on Si micropillar arrays for performance enhancement of piezoelectric nanogenerators.
abstract: Enhanced output power from a ZnO nanorod (NR)-based piezoelectric nanogenerator (PNG) is demonstrated by forming a heterojunction with Si micropillar (MP) array. The length of the SiMP array, which was fabricated by electrochemical etching, was increased systematically from 5 to 20 μm by controlling the etching time. Our structural and optical investigations showed that the ZnO NRs were grown hierarchically on the SiMPs, and their crystalline quality was similar regardless of the length of the underlying SiMPs. The peak output voltage from the ZnO NR-based PNG was greatly increased by ∼5.7 times, from 0.7 to 4.0 V, as the length of the SiMP arrays increased from 0 (flat substrate) to 20 μm. The enhancement mechanism was explained based on the series connection of the ZnO NRs regarded as a single source of piezoelectric potential by creating a heterojunction onto the SiMP arrays.
authors.affiliation: †Department of Electronic Engineering, Yeungnam University, Gyeongbuk 712-749, South Korea.
authors.forename: Md Roqibul
authors.initials: MR
authors.lastname: Hasan
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Baek
authors.affiliation: †Department of Electronic Engineering, Yeungnam University, Gyeongbuk 712-749, South Korea.
authors.forename: Kwang Su
authors.initials: KS
authors.lastname: Seong
authors.forename: Jae Hyun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: †Department of Electronic Engineering, Yeungnam University, Gyeongbuk 712-749, South Korea.
authors.forename: Il-Kyu
authors.initials: IK
authors.lastname: Park
keywords: ZnO nanorods; heterojunction; hierarchical nanostructures; piezoelectric nanogenerators