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Nanomaterials 2018, 8(6), 437; https://doi.org/10.3390/nano8060437

Stable and High Piezoelectric Output of GaN Nanowire-Based Lead-Free Piezoelectric Nanogenerator by Suppression of Internal Screening

1
Department of Physics, Chonnam National University, Gwangju 61186, Korea
2
Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 61186, Korea
*
Author to whom correspondence should be addressed.
Received: 30 April 2018 / Revised: 4 June 2018 / Accepted: 11 June 2018 / Published: 14 June 2018
(This article belongs to the Special Issue 1D Nanostructure-Based Piezo-Generators)
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Abstract

A piezoelectric nanogenerator (PNG) that is based on c-axis GaN nanowires is fabricated on flexible substrate. In this regard, c-axis GaN nanowires were grown on GaN substrate using the vapor-liquid-solid (VLS) technique by metal organic chemical vapor deposition. Further, Polydimethylsiloxane (PDMS) was coated on nanowire-arrays then PDMS matrix embedded with GaN nanowire-arrays was transferred on Si-rubber substrate. The piezoelectric performance of nanowire-based flexible PNG was measured, while the device was actuated using a cyclic stretching-releasing agitation mechanism that was driven by a linear motor. The piezoelectric output was measured as a function of actuation frequency ranging from 1 Hz to 10 Hz and a linear tendency was observed for piezoelectric output current, while the output voltages remained constant. A maximum of piezoelectric open circuit voltages and short circuit current were measured 15.4 V and 85.6 nA, respectively. In order to evaluate the feasibility of our flexible PNG for real application, a long term stability test was performed for 20,000 cycles and the device performance was degraded by less than 18%. The underlying reason for the high piezoelectric output was attributed to the reduced free carriers inside nanowires due to surface Fermi-level pinning and insulating metal-dielectric-semiconductor interface, respectively; the former reduced the free carrier screening radially while latter reduced longitudinally. The flexibility and the high aspect ratio of GaN nanowire were the responsible factors for higher stability. Such higher piezoelectric output and the novel design make our device more promising for the diverse range of real applications. View Full-Text
Keywords: GaN nanowires; nanogenerator; piezoelectricity; flexible electronics; free-carrier screening GaN nanowires; nanogenerator; piezoelectricity; flexible electronics; free-carrier screening
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Johar, M.A.; Hassan, M.A.; Waseem, A.; Ha, J.-S.; Lee, J.K.; Ryu, S.-W. Stable and High Piezoelectric Output of GaN Nanowire-Based Lead-Free Piezoelectric Nanogenerator by Suppression of Internal Screening. Nanomaterials 2018, 8, 437.

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