Abstract
Large-area piezoelectric ZnO films with different gran size has been synthesized by sol-gel technique using different annealing temperatures from 550 to 700°C. The piezoelectric efficiency (PE) of those deposited films is characterized by Piezoelectric Force Microscopy (PFM). All synthesized films exhibit a crystal structure. The width of the rock curve of [0002] characterized by x-ray diffraction decreases with the annealing temperature, suggesting a better c-axis orientated ZnO film formed at higher annealing temperature. The grain size of the grown films are found to continuously increase from 20 to 60 nm when the annealing temperatures increase from 550 to 700°C. The piezoelectric efficiency (PE, d33) of the films exhibit strong grain size dependence, i.e., the PE initially increase with the annealing temperature and then decreasing with a further annealing temperature increased. The maximum PE value appears in the film annealed at 650°C. The peculiar piezoelectric properties (d33) can be explained by the competing between the crystalline, which favors a larger d33 due to the enhanced dipole polarization, and the grain size, which results in a piezoforce release at large grain size due to domain wall size and motion.
Highlights
In vivo sensors have a wide application for real-time biomedical monitoring [1]
These results indicate that the crystallinity of the ZnO thin films is enhanced as the annealing temperature is increased
High-quality ZnO thin films with preferred c-axis orientation are prepared on single-crystal Si (100) via sol-gel growth method and annealed in the temperature range of 550 to 700°C
Summary
In vivo sensors have a wide application for real-time biomedical monitoring [1]. Single-use or non-rechargeable batteries to support implanted device limits the application of those promising implanted sensors, because of requiring to be surgically replaced at the end. The nanogenerator based on ZnO nanowire has demonstrated to enable the collection of the energy from the environmental mechanical energy and to drive electrical device in the microwatt power range [36]. The fundamental mechanism of a nanogenerator (NG) is related to a piezoelectric potential generated in nano wire (NW) under an external force, and a current flows on a loading resistor [7,8]. Such prototyping work has demonstrated the basic principle of the nanogenerator, the performance must drastically improve to make nanogenerators for practical applications. It is necessary to develop strategies towards achieving cost-effective NG in order to consistently scavenge the mechanical energy from the environmental sources
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