A large area bimaterial sheet of piezoelectric nanogenerators for energy harvesting: Effect of RF sputtering on ZnO nanorod

In this work, we have developed an optimal radio frequency (RF) sputtering process (sputtering power, sputtering time, and target type) to grow a ZnO seed layer on an indium tin oxide (ITO) glass followed by the hydrothermal growth of a well-aligned perpendicular ZnO nanorod array for the fabrication of a piezoelectric nanogenerator. The change in nanorod morphology, crystallinity, orientation, growth rate, diameter, length, and number density of ZnO nanorods were controlled by modifying various processing parameters. A prior seeding of ZnO nanoparticle with good wurtzite structure and with preferred orientation along the (0 0 2) direction of the crystal is critical for the subsequent growth of well-aligned vertically oriented ZnO nanorods on ITO substrates. A large area (2 x 2 cm(2)) of the piezoelectric nanogenerator bimaterial sheet was fabricated by combining the vertically grown ZnO nanorod array electrode with an Au-coated polyurethane (PU) film as the other electrode. By rubbing the two electrodes together, the nanodevice generates an optimal output current density of about 1 1 mu A/cm(2). The result demonstrates that the optimal seeding process and shows the potential to convert the mechanical energy to electrical current generation as a nanodevice. (C) 2010 Elsevier B.V. All rights reserved.