Simultaneously inducing preferred crystalline orientation with a strong piezoelectric response in polycrystalline aluminum nitride (AlN) thin films by atomic layer deposition is a technical challenge due to the upscaling of the integration of piezoelectric functionalities, such as sensing and actuation, in micro-devices without any poling process. Utilizing low-temperature plasma-enhanced atomic layer deposition (PE-ALD), highly c-axis-oriented AlN films have been prepared with precise control over the relative composition, purity levels, and chemical states of constituent elements. Tailoring thermodynamic parameters, such as the growth temperature and purging time after the trimethylaluminum precursor pulsing before the N2:H2:Ar plasma reaction, provide the possibility of modulating the texture coefficient and the relative piezoelectric response. The effective transverse piezoelectric e31,f coefficient of 0.37 C/m2 was achieved on the AlN film grown at 250 °C and 30 s with the highest texture coefficient TC(002) of 2.75 along the c-axis orientation. The process proposed, at a low temperature with the highly conformal growth of aluminum nitride thin films by PE-ALD, opens up pathways to design novel piezoelectric functional materials for micro-electro-mechanic system devices with complementary metal oxide semiconductor process temperature compatibility.
The growth process of zinc oxide (ZnO) thin films by atomic layer deposition (ALD) accompanied by the presence of oxygen gas pulsing is investigated by means of the isotopic tracking of oxygen 18O from the water precursor and oxygen 16O from the gas.
This study reports
a strong ME effect in thin-film composites consisting
of nickel, iron, or cobalt foils and 550 nm thick AlN films grown
by PE-ALD at a (low) temperature of 250 °C and ensuring isotropic
and highly conformal coating profiles. The AlN film quality and the
interface between the film and the foils are meticulously investigated
by means of high-resolution transmission electron microscopy and the
adhesion test. An interface (transition) layer of partially amorphous
Al
x
O
y
/AlO
x
N
y
with thicknesses
of 10 and 20 nm, corresponding to the films grown on Ni, Fe, and Co
foils, is revealed. The AlN film is found to be composed of a mixture
of amorphous and nanocrystalline grains at the interface. However,
its crystallinity is improved as the film grew and shows a highly
preferred (002) orientation. High self-biased ME coefficients (αME at a zero-bias magnetic field) of 3.3, 2.7, and 3.1 V·cm–1·Oe–1 are achieved at an off-resonance
frequency of 46 Hz in AlN/Ni thin-film composites with different Ni
foil thicknesses of 7.5, 15, and 30 μm, respectively. In addition,
magnetoelectric measurements have also been carried out in composites
made of 550 nm thick films grown on 12.5 μm thick Fe and 15
μm thick Co foils. The maximum magnetoelectric coefficients
of AlN/Fe and AlN/Co composites are 0.32 and 0.12 V·cm–1·Oe–1, measured at 46 Hz at a bias magnetic
field (H
dc) of 6 and 200 Oe, respectively.
The difference of magnetoelectric transducing responses of each composite
is discussed according to interface analysis. We report a maximum
delivered power density of 75 nW/cm3 for the AlN/Ni composite
with a load resistance of 200 kΩ to address potential energy
harvesting and electromagnetic sensor applications.
Over the last few decades, manipulating the metal-insulator (MI) transition in perovskite oxides (ABO3) via an external control parameter has been attempted for practical purposes, but with limited success. The substitution of A-site cations is the most widely used technique to tune the MI transition. However, this method introduces unintended disorder, blurring the intrinsic properties. The present study reports the modulation of MI transitions in [10 nm-NdNiO3/t-LaNiO3/10 nm-NdNiO3/SrTiO3 (100)] trilayers (t = 5, 7, 10, and 20 nm) via the control of the LaNiO3 thickness. Upon an increase in the thickness of the LaNiO3 layer, the MI transition temperature undergoes a systematic decrease, demonstrating that bond disproportionation, the MI, and antiferromagnetic transitions are modulated by the LaNiO3 thickness. Because the bandwidth and the MI transition are determined by the Ni-O-Ni bond angle, this unexpected behavior suggests the transfer of the bond angle from the lower layer into the upper. The bond-angle transfer eventually induces a structural change of the orthorhombic structure of the middle LaNiO3 layer to match the structure of the bottom and the top NdNiO3, as evidenced by transmission electron microscopy. This engineering layer sequence opens a novel pathway to the manipulation of the key properties of oxide nickelates, such as the bond disproportionation, the MI transition, and unconventional antiferromagnetism with no impact of disorder.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.