Gallium nitride (GaN) and aluminium gallium nitride (AlGaN) are
promising materials for optoelectronics because of their direct band
gap and high electron mobility. However, their optical absorbance
being limited to within the ultraviolet (UV) range constrains their
deployment in broadband photodetectors. Here, we combine three-dimensional
(3D) epitaxial GaN and AlGaN thin films with visible-spectrum active
two-dimensional (2D) molybdenum disulphide (MoS2) to create
a 2D/3D hybrid that is active across a broadband spectrum. The interfacial
properties of 2D/3D heterojunctions are thoroughly investigated on
an industrially compatible silicon platform where a staggered gap
(type II) band structure leads to a rectifying heterojunction phenomenon.
It is shown that the optical absorbance spectra can be broadened by
several hundreds of nanometers using this hybrid approach. As a result,
these heterostructures are promising to cover broadband photodetection
from ultraviolet (UV)-A (UV-B) to visible solar spectrum, thereby
enhancing the practical utility of GaN and its alloys.
In this report, the ferromagnetic shape memory alloy (Ni50Mn35In15) and Pb0.96La0.04Zr0.52Ti0.48O3 based bilayer (Ni-Mn-In/PLZT (260 nm/300 nm)), trilayer (Ni-Mn-In/PLZT/Ni-Mn-In (130 nm/300 nm/130 nm)) and four-layer (Ni-Mn-In/PLZT/Ni-Mn-In/PLZT (130 nm/150 nm/130 nm/150 nm)) multiferroic heterostructures with equal thickness ratios have been fabricated over Si substrates via DC/RF magnetron sputtering technique. The in-plane and out-of-plane magnetic hysteresis curves show the anisotropic nature of the ferromagnetic layer. The anisotropic magnetoelectric coupling characteristics have been investigated for all the fabricated devices by recording the induced magnetoelectric coupling voltages under both parallel and perpendicular applied magnetic fields to the plane of the device. Compared to all fabricated heterostructures, the trilayer structure exhibits the highest magnetoelectric coupling coefficients with 1.56 V/(cm Oe)-1 and 2.01 V/(cm Oe)-1 in longitudinal and transverse configurations, respectively. This anisotropic nature of magnetoelectric coupling can be used to measure the applied magnetic field direction. The rarely reported anisotropic AC magnetic field sensing parameters of the fabricated devices like Pearson’s r, sensitivity, and inaccuracy have been calculated. The trilayer device exhibits excellent AC magnetic field sensing parameters with inaccuracy, sensitivity, and linearity of 1.856% full-scale output (FSO), 0.63 mV cm−1 and 0.9993 in longitudinal configuration while 1.755% FSO, 1.18 mV Oe−1, and 0.9993 in the transverse configuration, respectively. Such nanoscale ferromagnetic shape memory alloys based symmetric multilayered multiferroic heterostructures pave the way for the design and development of futuristic MEMS magnetoelectric magnetic field sensor to detect the magnetic field and its spatial orientation.
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