Magnetic field imaging by hBN quantum sensor nanoarray

Abstract

Placing a sensor close to the target at the nano-level is a central challenge in quantum sensing. We demonstrate magnetic field imaging with a boron vacancy (VB−) defects array in hexagonal boron nitride with a few 10 nm thickness. VB− sensor spots with a size of (100 nm)2 are arranged periodically with nanoscale accuracy using a helium ion microscope and attached tightly to a gold wire. The sensor array allows us to visualize the magnetic field induced by the current in the straight micro wire with a high spatial resolution. Each sensor exhibits a practical sensitivity of 73.6 μT/Hz0.5, suitable for quantum materials research. Our technique of arranging VB− quantum sensors periodically and tightly on measurement targets will maximize their potential.

Nitrogen isotope effects on boron vacancy quantum sensors in hexagonal boron nitride

“…Its electron spin is localized around the vacancy site and is significantly affected by the three nearest nitrogen nuclear spins. Stable isotopes of nitrogen are 14 N and 15 N. The natural composition ratio of 14 N is 99.6%, and 15 N is almost nonexistent (0.4%). The nuclear spin is one of the major differences between these isotopes.…”

“…8,9) Recently, it has been discovered that electron spins of boron vacancy (V B ) defects in hexagonal boron nitride (hBN) can be used as quantum sensors even at room temperature. [10][11][12][13][14][15] A V B defect has a structure in which a boron atom in hBN is replaced by a vacancy [Fig. 1(a)].…”

“…The nuclear spin is one of the major differences between these isotopes. Since 15 N spin (I = 1/2) is only half of the 14 N spin (I = 1), V B defects in 15 N isotopically enriched hBN have fewer energy levels than in non-treated hBN. The fewer levels and the higher the occupancy, the stronger and less overlapping each resonance signal will be.…”

“…[16][17][18][19] Here, we investigate nitrogen isotope-enriched hBN and observe nitrogen isotope effects on the optically detected magnetic resonance (ODMR) spectrum of V B defects. We synthesized the isotopically controlled hBN crystals using a metathesis reaction under high pressure 20,21) with commercially available 15 NH 4 Cl. The Raman shifts of the samples are scaled with their reduced mass, which is the effective mass for an equivalent one-body problem of the two-body vibration problem for boron and nitrogen atoms, consistent with previous work on boron isotope enrichment.…”

“…The Raman shifts of the samples are scaled with their reduced mass, which is the effective mass for an equivalent one-body problem of the two-body vibration problem for boron and nitrogen atoms, consistent with previous work on boron isotope enrichment. We perform ODMR measurements of V B defects produced by helium ion implantation and determine the magnitude of the HFI parameter of 15 N spin to be 64 MHz. The observed significant modification of resonance spectra due to 15 N isotope enrichment will help improve sensitivity, control fidelity, and precise positioning of quantum sensors.…”