Fabrication and use of nanocoils on nitrogen-vacancy diamond substrates for magnetic field detection and manipulation
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.
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 . The spiral inductor of claim 1 , wherein the spiral nanocoil has a turn spacing that is no larger than 500 nm.
3 . The spiral inductor of claim 1 , wherein the spiral nanocoil has a turn spacing that is no larger than 250 nm.
4 . The spiral inductor of claim 1 , wherein the spiral nanocoil has a diameter that is no greater than 100 μm.
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 . 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 . The spiral inductor of claim 1 , wherein the electrically conductive material is a titanium/gold bilayer.
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 . 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 . 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 . The magnetic field sensor of claim 10 , comprising the green light-emitting laser, wherein the green light-emitting laser is a pulsed laser.
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 . 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 . 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 . 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 . The method of claim 15 , wherein the electron-beam resist is poly(methyl methacrylate).
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.