Sputter Deposited Magnetostrictive Layers for SAW Magnetic Field Sensors

Abstract

For the best possible limit of detection of any thin film-based magnetic field sensor, the functional magnetic film properties are an essential parameter. For sensors based on magnetostrictive layers, the chemical composition, morphology and intrinsic stresses of the layer have to be controlled during film deposition to further control magnetic influences such as crystallographic effects, pinning effects and stress anisotropies. For the application in magnetic surface acoustic wave sensors, the magnetostrictive layers are deposited on rotated piezoelectric single crystal substrates. The thermomechanical properties of quartz can lead to undesirable layer stresses and associated magnetic anisotropies if the temperature increases during deposition. With this in mind, we compare amorphous, magnetostrictive FeCoSiB films prepared by RF and DC magnetron sputter deposition. The chemical, structural and magnetic properties determined by elastic recoil detection, X-ray diffraction, and magneto-optical magnetometry and magnetic domain analysis are correlated with the resulting surface acoustic wave sensor properties such as phase noise level and limit of detection. To confirm the material properties, SAW sensors with magnetostrictive layers deposited with RF and DC deposition have been prepared and characterized, showing comparable detection limits below 200 pT/Hz1/2 at 10 Hz. The main benefit of the DC deposition is achieving higher deposition rates while maintaining similar low substrate temperatures.

Magnetosensory Power Devices Based on AlGaN/GaN Heterojunctions for Interactive Electronics

“…The designed MPD is based on the cantilever-structured AlGaN/GaN high-electronmobility transistor (HEMT), in which a magnetic thin film ((Fe 90 Co 10 ) 78 Si 12 B 10 ) is deposited on the front end of the cantilever. [37][38][39][40] The enlarged part is the schematic cross-section of the AlGaN/GaN HEMT, where from top to bottom are AlGaN, AlN, GaN, and Si substrates. The thicknesses of AlGaN, AlN, and GaN layers are 30 nm, 1 nm, and 4.3 µm, respectively, and the active region of MPD is 34 × 34 µm 2 , as shown in Supplementary Table S1.…”

High sensitivity magnetoelastic surface acoustic wave (SAW) magnetic field sensors

“…32 and specific characteristics of the sensor used for this study can be found in Ref. 33. The sensing principle of SAW magnetic field sensors is based on the magneto-elastically induced change of the Young's modulus which leads to a phase modulation of the propagating acoustic wave by the applied magnetic field.…”

Magnetoelectric MEMS Magnetic Field Sensor Based on a Laminated Heterostructure of Bidomain Lithium Niobate and Metglas

“…FeGaC [ 14 ] and FeCoC [ 15 ] thin films exhibit the highest piezomagnetic coefficients (q) of 10 ppm/Oe. However, for ME MEMS, FeCoSiB with a comparable q = 5 ppm/Oe is mostly used [ 13 , 16 ]. Magnetically soft metglas thin films are most interesting for detecting ultraweak magnetic fields due to the high values of the piezomagnetic coefficient in low magnetic fields, which makes it possible to create self-biased devices [ 17 ].…”

“…Magnetically soft metglas thin films are most interesting for detecting ultraweak magnetic fields due to the high values of the piezomagnetic coefficient in low magnetic fields, which makes it possible to create self-biased devices [ 17 ]. However, in the technology of deposition of MS metglas layers, there are several problems associated with the crystallization process in the films due to the heating of substrate during the magnetron sputtering, stresses in the sputtered film and associated magnetic anisotropies [ 16 , 18 ]. In FeCoSiB, MS properties strongly depend on the degree of amorphization of thin films [ 19 , 20 ].…”