Hydrothermal Fabrication and Ferroelectric Behavior of Lithium-Doped Zinc Oxide Nanoflakes

Lithium-doped zinc oxide nanoflakes were hydrothermally fabricated in aqueous solutions of zinc nitrate, hexamethylenetetramine and lithium chloride. The success of lithium doping was confirmed by inductively coupled plasma-atomic emission spectrometry and secondary ion mass spectrometry. Furthermore, Raman and photoluminescence spectroscopies indicated that a proportion of the lithium impurities in the zinc oxide samples substituted zinc ions in the crystal lattice. The polarization versus applied field curves of the lithium-doped zinc oxide samples appeared to be hysteresis loops, suggesting that the samples were ferroelectric. The ferroelectricity of the lithium-doped zinc oxide samples is attributed to a variety of possible electric dipoles related to substitutional lithium ions present in the lattice of zinc oxide. The remnant polarizations and coercive fields of the samples were in the order of 10(-3)-10(-2) mu C/cm(2) and 10(4)-10(5) V/m, respectively. It was also found that the remnant polarizations and coercive fields of the samples did not increase monotonously with the content of lithium impurities.