High-Sensitivity Isotopically-Purified All-Electrical Chip-Scale Atomic Magnetometers

All-electrical chip-scale atomic magnetometers based on spin-coherent transport effects through atomistic defects in semiconductors will have orders of magnitude improved sensitivity if the semiconductor hosts are isotopically purified and related device parameters optimized. Current all-electrical chip-scale atomic magnetometers have room-temperature sensitivities ~400 nT/root-Hz, and the proposed innovation we estimate conservatively to provide room-temperature sensitivities of 400 pT/root-Hz with possibilities as low as 100 pT/root-Hz. These are comparable to those achievable with NV-diamond chip-scale atomic magnetometers, but without the requirement for microwave fields or optical elements. These small-scale magnetometers would avoid the need to self-calibrate, compared to fluxgate magnetometers, and avoid challenges related to diffusion of gas through a glass cell and radiation damage of fiberoptics. They would thus be very well suited for NASA missions and nanosats as their size, power, and complexity restrictions are most severe. In Phase II we plan to build a bench-top prototype based on microscopic- and device-level models of the spin-dependent dynamics in SiC-based all-electrical magnetometer developed in Phase I. Our Phase I results confirmed the dramatically improved sensitivity to magnetic fields in isotopically purified SiC. We will work with our partners to conduct further device design, epilayer growth, device fabrication and characterization in an iterative development cycle that will culminate in the second year where our objective is to demonstrate a magnetometer prototype that meets the targeted device performance in NASA-relevant environments as assessed by JPLs mu-house facility. All-electrical chip-scale atomic magnetometers based on spin-coherent transport effects through atomistic defects in semiconductors will provide room-temperature sensitivities of 400 pT/root-Hz with possibilities as low as 100 pT/root-Hz if the semiconductor hosts are isotopically purified and device parameters optimized. These are comparable to NV-diamond chip-scale atomic magnetometers, but without the microwave fields or optical elements. These magnetometers avoid the need to self-calibrate, compared to fluxgate magnetometers, and avoid challenges of diffusion of gas through a glass cell and radiation damage of fiberoptics.The improved size, weight, and power consumption of these highly stable small-scale all-electrical SiC-based magnetometers make them ideal for sensor redundancy, nanosats, and cancellation of magnetic distortions due to spacecraft stray fields. Implications include search for life (water vapor and subsurface oceans), crustal anomalies for planetary magnetic history, studies of atmospheric loss by solar wind, and space mining of metal-rich asteroids. In Phase II we will build a bench-top prototype based on microscopic- and device-level models of the spin-dependent dynamics in SiC-based all-electrical magnetometer developed in Phase I, and with predictions shown in this chart’s figure of a 1000-times narrower magnetic-field-dependent current than current state of the art. We will conduct, with subcontractors General Electric Research and Penn State University, further device design, isotopically purified epilayer growth, device fabrication and characterization in an iterative development cycle. We will obtain six isotopically-purified epilayers and will be processed into optimized pin diodes, and then tested for spin-coherent transport (narrow-feature near-zero-field magnetoresistance) at Penn State and QuantCAD. The best diodes will be tested at JPL for sensitivity and stability, including in the mu-house facility that simulates the magnetic fields during recent spacecraft flybys in planetary missions. The best diodes will be incorporated into our prototype that will continue to be optimized through the second year where our objective is to demonstrate the targeted device performance in NASA-relevant environments as assessed by JPL’s mu-house facility. The proposed deliverable is the magnetometer with sub 400 pT/root-Hz sensitivity, validated at JPL and with stability and implications for planetary missions assessed.

Using an all-electrical readout these highly stable small-scale all-electrical SiC-based magnetometers do not require high-frequency microwave elements or optical components. Their improved size, weight and power consumption make them ideal for sensor redundancy, nanosats and cancellation of magnetic distortions due to spacecraft stray fields. Implications include search for life (water vapor, subsurface oceans), crustal anomalies for planetary magnetic history, studies of atmospheric loss by solar wind and space mining of metal-rich asteroids. All-electrical chip-scale magnetometers have applications in aerospace, health, geological prospecting and noninvasive materials monitoring. Examples include magnetic navigation for GPS-denied airborne applications, magnetocardiography, underground/underwater anomalies, planetary probing and solar weather monitoring, and high-resolution crack detection. 

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