Vanderbilt researchers have developed a method for forming a film of lanthanide oxide nanoparticles using electrophoretic deposition. This technique is straightforward to set up and provides thickness control at high deposition rates, enabling site selective particle assembly for any size and shape.
Lanthanide oxides such as europium oxide (Eu2O3) and gadolinium oxide (Gd2O3) are known for their light emitting and high-k dielectric properties, respectively. The Eu3+-doped Gd2O3, in microcrystalline form, has been employed in video displays and tri-color fluorescent lamps as a red phosphor. Recently, the nanocrystalline form of Eu3+-doped sesquioxides has gained research interest due to its potential use in luminescent biological tags, efficient light emitting devices, and high-resolution displays. Similarly, Gd2O3 has received research attention because of its high-k dielectric properties and it has been proposed as a silicon dioxide replacement for gate oxide in ultra-small complementary metal-oxide-semiconductor (CMOS) devices. However, because most applications of luminescent and dielectric materials require their implementation in thin-film form, Eu2O3 and Gd2O3 nanocrystals need to be assembled into thin-film form to study their optical and dielectric properties.
The method utilizes two substrates that are positioned apart from one another and have a voltage applied between them. Upon immersion of the substrates into a solution comprised of lanthanide oxide nanoparticles suspended in hexane, a film of lanthanide oxide nanoparticles forms on the conducting surface of one of the substrates. Upon completion of this immersion step, the substrate with the nanoparticles is exposed to air while the voltage continues to be applied, effectively drying the film of lanthanide oxide nanoparticles onto the substrate.
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Figure 1: The capacitance and voltage characteristics of a metal-oxide semiconductor capacitor that was fabricated from nanocrystal films using the developed method is shown here.