title: Transparent, Flexible Piezoelectric Nanogenerator Based on GaN Membrane Using Electrochemical Lift-Off.
abstract: A transparent and flexible piezoelectric nanogenerator (TF PNG) is demonstrated based on a GaN membrane fabricated by electrochemical lift-off. Under shear stress on the TF PNG by finger force (∼182 mN), the GaN membrane effectively undergoes normal stress and generates piezoelectric polarization along the c-axis, resulting in the generation of piezoelectric output from the TF PNG. Although the GaN layer is 315 times thinner than the flexible polyethylene terephthalate (PET) substrate, the low Young's modulus of PET allows the GaN membranes to absorb ∼41% of the applied strain energy, which leads to their large lattice deformation under extremely low applied stress. Maximum output voltage and current values of 4.2 V and 150 nA are obtained, and the time decay of the output voltage is discussed.
authors.affiliation: Department of Physics, Chonnam National University , Gwangju 61186, Republic of Korea.
authors.forename: Jin-Ho
authors.initials: JH
authors.lastname: Kang
authors.affiliation: Department of Physics, Chonnam National University , Gwangju 61186, Republic of Korea.
authors.forename: Dae Kyung
authors.initials: DK
authors.lastname: Jeong
authors.affiliation: Department of Physics, Chonnam National University , Gwangju 61186, Republic of Korea.
authors.forename: Sang-Wan
authors.identifier: http://orcid.org/0000-0002-6093-1734
authors.initials: SW
authors.lastname: Ryu
keywords: GaN; electrochemical etching; energy-harvesting device; flexible electronics; piezoelectric nanogenerators