Deep boron diffusion often induces residual stress in bulk micromachined MEMS structures, which may affect the MEMS devices operation. In this study, we studied the modal patterns of MEMS vibratory gyroscope under the residual stress (100 – 1000 MPa). Modal patterns and modal frequencies of the gyro are found to be dependent on the residual stress values. Without any residual stress, the modal frequencies drive and sense modeswere found to be 20.06 kHz and 20.36 kHz respectively. In presence of 450 MPa residual stress, the modal frequencies of the drive and sense modes were changed to 42.75 kHz and 43.07 kHz respectively.
Metal oxide based hetero-structures (like Pb (ZrxTi1-x) O3 – ZnO) can be used for wide variety of future sensors and electronic devices. This paper presents growth and electrical properties of nano-textured (110) Pb (Zr0.52Ti0.48) O3/ (001) ZnO hetrostructure on oxidized silicon substrate by RF sputtering technique. The grain sizes of ZnO and PZT films are found to be around 30 nm and 80 nm respectively. Resistivity of the ZnO layer is found to be 1x10 9 ?-cm. The electrical properties of the film are studied by creating in-plane electrodes on top of the PZT/ZnO hetrostructure film. The remnant polarization of the film is found ~ 47 µC/ cm 2 at 200 kV/ cm 2 . Dielectric constant of the film is found to be 300 at 1 kHz. The film also showed a low leakage current density of ~ 10 -5 A/cm 2 at 200 kV/ cm applied electric field. The nano-textured (110) Pb (Zr0.52Ti0.48) O3/ (100) ZnO hetrostructure integrated with inter-digital-transducers and microelectronic is well suitable for low-cost, robust, programmable passive micro sensors for military structure and systems such as aircraft, missiles.
Aluminum nitride (AlN) films were grown on Si substrates by dc magnetron sputtering in plasma containing a mixture of argon and nitrogen, using a pure aluminum target. In this paper, we studied the growth of AlN films on Si(100) substrates under varying gas ratio (N2 to Ar gas ratio) by DC reactive magnetron sputtering at moderate deposition temperature (400°C-600°C). Phase formation and orientation of the thin films were determined by Grazing Incidence X-Ray Diffraction (GIXRD). Surface morphology of the deposited thin films was investigated by Scanning Electron Microscope. Film orientations were studied by varying the gas ratio and deposition temperature to obtain (002) oriented film. The highest Texture coefficient along (002) direction (γ=3.2) is obtained for optimized growth condition at Argon to Nitrogen gas ratio 10:10 and substrate temperature 550°C. This oriented film can be used in MEMS based devices.
Nowadays, flexible magnetoelectric (ME) heterostructures comprising lead-free piezoelectrics are of considerable interest for commercializing wearable electronic devices such as energy harvesters, nonvolatile memory, implantable medical diagnostics, and sensors. Here, we fabricate a highly flexible, cost-effective, nanostructured magnetic field sensor comprising an AlN/Ni–Mn–In ME heterostructure over Ni foils. The functionality of the AlN/Ni–Mn–In/Ni heterostructure has been investigated by measuring the magnetodielectric MD (%) and magnetoelectric coupling (αME) coefficient with Ni–Mn–In thickness, anisotropy, and flexibility. The thickness ratio of piezoelectric AlN (∼400 nm) and magnetostrictive Ni–Mn–In (∼385 nm) layers has been optimized to achieve the high performance of the magnetic sensor. The encapsulation of the Ni–Mn–In layer drastically enhances the performance of the fabricated heterostructure. The highest MD ∼ 2.95% and αME ∼ 3.2 V/cm·Oe have been recorded with an equal thickness ratio of AlN and Ni–Mn–In layers. It could be ascribed to the large magnetostrictive strain transferred to the AlN piezoelectric layer, which enhances the induced ME voltage. Moreover, the nonzero value of αME at zero bias magnetic field has been observed and related to the piezomagnetic coefficient (q) grading in the Ni–Mn–In(+q)/Ni(−q) ferromagnetic system, which enhances the strength of magnetoelectric coupling. The fabricated device has easily detected the ultralow magnetic field of up to or less than ∼1 μT. In addition, the anisotropic functionality of the device has been explained by measuring the magnetodielectric and magnetoelectric characteristics in parallel and perpendicular dc bias fields. The MD and ME characteristics remain stable up to 2500 bending cycles. Hence, the present lead-free ME heterostructure integrated over a flexible Ni foil can enhance the multifunctionality of futuristic flexible magnetic field sensors for room-temperature applications.
In this study, the effect of ZnO buffer layer on the electrical properties of PbZrTiO3/BiFeO3 (PZT/BFO) multilayers has been reported. For this, PZT/BFO multilayers were spin-coated with and without ZnO buffer layer on platinized silicon wafers. X-ray diffraction results of both the films showed polycrystalline phase pure perovskite structure. Both the films show a dense and homogeneous grain structure. The electric properties of the films were measured. The ZnO buffered multilayer thin film showed ∼3 times improvement in remnant polarization compared to the multilayer thin film with no buffer. The buffered samples were found to have higher dielectric constant (1000 at 100 Hz) compared to that of sample (580 at 100 Hz)) with no buffer. Dielectric constants of both the films were found to be ∼30% tunable at 5 V. The buffered film also showed low leakage current density and higher dielectric breakdown compared to the multilayer thin film without buffer.
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