Abstract
In this work, the dependence of piezoelectric coefficients (PE) on the size of artificial fabricated ZnO micropillars on Si substrate is investigated. ZnO full film is grown with c-axis orientation and an average grain size of 20 nm at a substrate temperature of 500 °C by pulsed laser ablation. The micropillars with the size range of 1.5 to 7 μm are formed by top-down semiconductor device processing. The PE, characterized by piezoelectric force microscopy (PFM), is found to increase from 18.2 to 46.9 pm/V, when the ZnO pillar size is reduced from 7 to 1.5 μm. The strong PE dependence on ZnO pillar size can be explained by local changes in polarization and reduction of unit cell volume with respect to bulk values. These results have strong implications in the field of energy harvesting, as piezoelectric voltage output scales with the piezoelectric coefficient.
Highlights
The fundamental principle of ZnO nanogenerator [1,2,3] is to utilize mechanical energy of the environment, which is available everywhere from irregular vibrations, human activity even noise with a wide spectrum of frequencies and time-dependent amplitudes
The lacking of high power output in current ZnO NW generation is partially attributed to the structural properties of piezoelectric material, especially imperfect c-axis oriented crystalline of ZnO NW material and low yield in the NW device [6]; both are synthesized by chemical methods
By following Riaz’s theoretical study [20], we have experimentally investigated piezoelectric size effects of man-made ZnO micropillars
Summary
The fundamental principle of ZnO nanogenerator [1,2,3] is to utilize mechanical energy of the environment, which is available everywhere from irregular vibrations, human activity even noise with a wide spectrum of frequencies and time-dependent amplitudes. The first prototyping of a nanogenarator based on ZnO piezoelectric nanowire (NW) arrays [4,5,6] has been demonstrated to be able to drive microsensor and sensor network nods in micropower range. It is still far away from a milli-power output source, which is required by most practical applications of individual sensors and sensor network systems. The lacking of high power output in current ZnO NW generation is partially attributed to the structural properties of piezoelectric material, especially imperfect c-axis oriented crystalline of ZnO NW material and low yield in the NW device [6]; both are synthesized by chemical methods. In the ZnO NW, the voltage potential generated from the bent nanowire is between the left and right sides of single nanowire, which
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