Low-Temperature Growth of AlN Films on Magnetostrictive Foils for High-Magnetoelectric-Response Thin-Film Composites

Abstract

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.

Self‐biased magnetoelectric composite for energy harvesting

“…87,117 Nguyen et al used plasma-enhanced atomic layer deposition (PE-ALD) technology to fabricate an aluminum nitride (AlN)/Ni thin-film composite at a low temperature of 250°C. 89 Due to the high zero-field q of Ni foil (1.4 ppm Oe −1 ), the AlN/Ni composite delivered a high SME coefficient. At a Ni foil thickness of 7.5, 15, and 30 μm, the maximum α SME observed at the offresonance frequency of 46 Hz was 3.3, 2.7, and 3.1 V cm −1 Oe −1 , respectively.…”

“…A Ni/BZT–BCT/Ni SME composite laminated with <011>‐oriented BZT–BCT piezoelectric layer and Ni layer realized a comparable α SME to that of the Ni/(PMN–PZT)/Ni (Ni/single‐crystal Pb(Mg 1/3 Nb 2/3 )O 3 –Pb(Zr,Ti)O 3 /Ni) lead‐based layered composite and was significantly higher than those of Ni/PZT/Ni composites 87,117 . Nguyen et al used plasma‐enhanced atomic layer deposition (PE–ALD) technology to fabricate an aluminum nitride (AlN)/Ni thin‐film composite at a low temperature of 250°C 89 . Due to the high zero‐field q of Ni foil (1.4 ppm Oe −1 ), the AlN/Ni composite delivered a high SME coefficient.…”

Recent Progress in Devices Based on Magnetoelectric Composite Thin Films

“…They found the ME voltage coefficient of 94.5 V/cm·Oe, which is large enough for harvesting electromagnetic energy for suitable applications. Nguyen et al [ 69 ] developed AlN/Ni, AlN/Fe, and AlN/Co thin-film ME composites and studied their energy-harvesting performance.…”

Anisotropy of the ΔE Effect in Ni-Based Magnetoelectric Cantilevers: A Finite Element Method Analysis

“…Nickel is also an easy-to-process material for thin-film applications and, compared to magnetostrictive compound materials, relatively simple to describe as a model system. Additionally, if necessary, it provides the possibility to be processed as a single crystalline material, e.g., an inverted stack allows the deposition of AlN on (polycrystalline) Ni foils, which can be replaced with single crystalline ones, with a high interface quality and c-axis orientation of AlN, resulting in a strong magnetoelectric response compared to Fe and Co [17]. Comparably few references can be found that target sensors in the microelectromechanical system (MEMS) regime [18][19][20], a highly interesting transition region where anisotropic material properties show increasing influence on the device characteristics, when the sensor dimensions start to reach the order of magnitude of individual crystals within the (poly-)crystalline material.…”