Significantly enhanced dielectric constant and energy density in Au/Al2O3 nanocomposite thin films

Nano-Au self-producing process was investigated to improve the dielectric properties of amorphous Al₂O₃ thin films via controlling the heat-treatment temperature. The results of high-resolution transmission electron microscopy (HTEM) showed that the nano-Au particles were uniformly dispersed in the amorphous Al₂O₃ matrix. More importantly, nano-Au particles could supply more space polarization charges and the dielectric constant of the nanocomposite thin film was enhanced from 8.2 to 32.2. As a result, the ultimate energy density was up to 13.3 J/cm³ with 2 mol% doping content, which is increased by about 137.5% compared to the pure counterpart. Furthermore, the thermally stimulated depolarization current (TSDC) analysis provided a powerful evidence to testify that the enhancement of the dielectric constant was originated from the trap charge polarization after the nano-Au doping. The finite element simulation results showed that the more space charges were generated around the nano-Au particles, which is more intuitive to understand the reason for the increase of the dielectric constant.