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US-12618924-B2 - Fabrication and use of nanocoils on nitrogen-vacancy diamond substrates for magnetic field detection and manipulation

US12618924B2US 12618924 B2US12618924 B2US 12618924B2US-12618924-B2

Abstract

Spiral inductors, magnetic field sensors incorporating the spiral inductors, and methods of using the magnetic field sensors are provided. The spiral inductors include an electrically conductive spiral coil and a nitrogen vacancy (NV) diamond substrate. A thin barrier layer of a dielectric material separates the spiral coil from the surface of the NV diamond substrate and an overlayer of dielectric material is disposed over the spiral nanocoil. The integration of the spiral coil with an NV substrate in this manner creates a highly enhanced magnetic transduction and produces a simple, high-performance way to control and read out electromagnetic signals. Because the spiral inductors enable electromagnetic-to-optical signal conversion, they can be used as sensors for environmental or biomedical applications and spin-based computation.

Inventors

  • Aviad Hai
  • Alireza Ousati Ashtiani
  • Ilhan Bok
  • Yash Sanjay Gokhale

Assignees

  • WISCONSIN ALUMNI RESEARCH FOUNDATION

Dates

Publication Date
20260505
Application Date
20240118

Claims (17)

  1. 1 . A spiral inductor comprising: a nitrogen vacancy diamond substrate; a barrier layer of dielectric material on a surface of the nitrogen vacancy diamond substrate; a spiral nanocoil comprising an electrically conductive material on a surface of the barrier layer of dielectric material; an overlayer of dielectric material disposed over the spiral nanocoil; a first electrode contact on a first end of the spiral nanocoil; and a second electrode contact on a second end of the spiral nanocoil.
  2. 2 . The spiral inductor of claim 1 , wherein the spiral nanocoil has a turn spacing that is no larger than 500 nm.
  3. 3 . The spiral inductor of claim 1 , wherein the spiral nanocoil has a turn spacing that is no larger than 250 nm.
  4. 4 . The spiral inductor of claim 1 , wherein the spiral nanocoil has a diameter that is no greater than 100 μm.
  5. 5 . The spiral inductor of claim 1 , wherein the barrier layer of dielectric material has a thickness that is no greater than 3 μm.
  6. 6 . The spiral inductor of claim 1 , wherein the dielectric material of the barrier layer and the dielectric material of the overlayer are independently selected from silicon oxides and silicon nitrides.
  7. 7 . The spiral inductor of claim 1 , wherein the electrically conductive material is a titanium/gold bilayer.
  8. 8 . The spiral inductor of claim 1 , wherein the spiral nanocoil is an octahedral spiral coil having a turn spacing that is no larger than 400 nm and a diameter that is no greater than 100 μm, and the barrier layer of dielectric material has a thickness that is no greater than 3 μm.
  9. 9 . A magnetic field detector comprising: a spiral inductor comprising: a nitrogen vacancy diamond substrate; a barrier layer of dielectric material on a surface of the nitrogen vacancy diamond substrate; a spiral nanocoil comprising an electrically conductive material on a surface of the barrier layer of dielectric material; an overlayer of dielectric material disposed over the spiral nanocoil; a first electrode contact on a first end of the spiral nanocoil; and a second electrode contact on a second end of the spiral nanocoil; an optical excitation source positioned to direct excitation radiation onto the nitrogen vacancy diamond substrate and the spiral nanocoil; and an optical detector positioned to detect a fluorescence signal generated by the nitrogen vacancy diamond.
  10. 10 . The magnetic field sensor of claim 9 , wherein the optical excitation source is a green light-emitting laser or light-emitting diode and the optical detector is a photon detector that detects red light.
  11. 11 . The magnetic field sensor of claim 10 , comprising the green light-emitting laser, wherein the green light-emitting laser is a pulsed laser.
  12. 12 . The magnetic field sensor of claim 9 , further comprising a microwave source configured to apply a microwave signal to the nitrogen vacancy diamond substrate.
  13. 13 . The magnetic field sensor of claim 12 , further comprising a static magnetic field generator positioned to apply a bias magnetic field across the surface of the nitrogen vacancy diamond substrate.
  14. 14 . A method of detecting a magnetic field generated by the spiral nanocoil in the magnetic field detector of claim 9 , the method comprising: directing excitation radiation from the optical excitation source onto the surface of the nitrogen vacancy diamond substrate and the spiral nanocoil, whereby the nitrogen vacancy diamond emits fluorescence having an intensity that is modulated by the magnetic field generated by the spiral nanocoil; and monitoring the fluorescence using the optical detector.
  15. 15 . A method of fabricating a spiral inductor, the method comprising: depositing a barrier layer of dielectric material on a surface of a nitrogen vacancy diamond substrate; forming a layer of an electron-beam resist on a surface of the barrier layer of dielectric material; defining a spiral nanocoil pattern in the layer of the electron-beam resist using positive electron-beam lithography; depositing an electrically conductive material in the spiral nanocoil pattern to form a spiral nanocoil comprising the electrically conductive material on the surface of the barrier layer of dielectric material; removing the remaining electron-beam resist from the surface of the barrier layer of dielectric material; depositing an overlayer of dielectric material over the spiral nanocoil; forming a first electrode contact on a first end of the spiral nanocoil; and forming a second electrode contact on a second end of the spiral nanocoil.
  16. 16 . The method of claim 15 , wherein the electron-beam resist is poly(methyl methacrylate).
  17. 17 . The method of claim 16 , wherein the positive electron-beam lithography is carried out with an electron beam dose in the range from 640 μC/cm 2 to 1600 μC/cm 2 and the spiral nanocoil has a turn spacing that is no larger than 500 nm and a diameter of less than 1 μm.

Description

REFERENCE TO GOVERNMENT RIGHTS This invention was made with government support under NS122605 awarded by the National Institutes of Health. The government has certain rights in the invention. BACKGROUND On-chip micro- and nano-fabricated inductors, antennas, and electromagnets extend possibilities for compartmentalizing a wide variety of technologies and research applications. From wireless communication, high frequency signal conversion, power transfer and filtering, to environmental and biological sensing-new designs are leveraging diverse geometries and material compositions to transform electromagnetic energy at a broad spatiotemporal range. Specific lab-on-chip platforms for magnetic detection and manipulation rely on patterned coils and loops for optical magnetometry, nuclear magnetic resonance (NMR) spectroscopy and imaging, magnetic particle separation, molecular magnetophoresis, and cell manipulation and labelling. Theoretical limitations and fabrication constraints restrict performance and are closely related to quality factor, frequency bandwidth, and temporal response. More recent innovative devices demonstrate improved properties by utilizing approaches such as three-dimensional fabrication, mechanically self-assembled coils, air-core or air-suspended coils, and the use of alternative materials such as graphene, carbon, ZnO, and others. However, the integration of complex designs into standard fabrication processes is not trivial. Consequently, metal-based flat spiral coils remain the mainstay devices for on-chip electromagnetic signal conversion owing to a relatively small number of lithography steps and higher structural and thermal stability. Spiral inductors are integrated in a myriad of recent applications including power harvesting components on flexible and bioresorbable electronic sensors, recording and stimulation devices for wireless neurological applications, and ingestible electroceuticals. Additionally, they empower modalities such as nuclear magnetic resonance (NMR) and biomedical magnetic resonance imaging (MRI) by providing high spatial resolution microprobes for spectroscopy and imaging. While most systems employ microlithography to pattern coil structures, a small number of studies began exploring nano-scale lithography to propel spatial features while maximizing performance. These include electron beam lithography (EBL) for synthesizing meandering inductors with submicron conducting lines, complementary metal-oxide semiconductor (CMOS)-compatible glancing angle physical vapor deposition (GLAD) for vertically aligned nanohelices, and spiral patterns realized via focused ion beam fabrication (FIB). (Stojanovic, G. et al., Scaling Meander Inductors from Micro to Nano. in 2006 International Semiconductor Conference vol. 1 93-96 (2006); Seilis, A. et al., IEEE Transactions on Components, Packaging and Manufacturing Technology 5, 675-684 (2015); Khorasani, S. A. Appl. Phys. Lett. 112, 031906 (2018).) The emerging integration of these methods and other promising nanofabrication techniques with standard CMOS processes, in particular EBL, highlights opportunities for designing novel rapid fabrication processes for high spatial resolution electromagnetic conversion. SUMMARY Spiral inductors, methods of fabricating the spiral inductors, magnetic field detectors incorporating the spiral inductors, and methods of using the magnetic field detectors are provided. One embodiment of a spiral inductor includes: a nitrogen vacancy diamond substrate; a barrier layer of dielectric material on a surface of the nitrogen vacancy diamond substrate; a spiral nanocoil comprising an electrically conductive material on a surface of the barrier layer of dielectric material; an overlayer of dielectric material disposed over the spiral nanocoil; a first electrode contact on a first end of the spiral nanocoil; and a second electrode contact on a second end of the spiral nanocoil. One embodiment of a magnetic field detector includes: a spiral inductor of a type described herein; an optical excitation source positioned to direct excitation radiation onto the nitrogen vacancy diamond substrate and the nanocoil; and an optical detector positioned to detect a fluorescence signal generated by the nitrogen vacancy diamond. One embodiment of a method of detecting a magnetic field generated by the spiral nanocoil in a magnetic field detector of a type described herein includes the steps of: directing excitation radiation from the optical excitation source onto the surface of the nitrogen vacancy diamond substrate and the nanocoil, whereby the nitrogen vacancy diamond emits fluorescence having an intensity that is modulated by the magnetic field generated by the spiral nanocoil; and monitoring the fluorescence using the optical detector. One embodiment of a method of fabricating a spiral inductor includes the steps of: depositing a barrier layer of dielectric material on a surface of a nitrogen vacancy diamond substra