Due to its coherent nitrogen-vacancy centers, controlled spin, sensitivity to magnetic fields, and ability to be employed at room temperature, diamond has long been the preferred material for quantum sensing. There hasn’t been much interest in researching diamond substitutes because such suitable material is simple to make and scale. However, diamond is not ideal for exploring quantum sensors and information processing. When diamonds get too small, the super-stable defect it’s renowned for begins to crumble. There is a limit at which a diamond becomes useless.
hexagonal boron nitride (hBN) has recently gained interest as spin defects for quantum information processing and quantum sensing by a layered material. However, the boron vacancy can exist in several charge states in the hBN lattice, but only the −1 state has spin-dependent photoluminescence and acts as a spin-photon interface.
The detection and investigation of the other charge states have so far proven to be difficult. This was a concern since the charge state is unstable and can flicker between the -1 and 0 states, characteristic of environments for quantum sensors and devices.
In a new study, scientists from TMOS, the ARC Centre of Excellence for Transformative Meta-Optical Systems, have developed a method to stabilize the –1 state and a new experimental approach for studying the charge states of defects in housing optical excitation and concurrent electron beam irradiation.
Their study has shown that hBN could replace diamond as the preferential material for quantum sensing and information processing. Scientists were able to stabilize the atomic defects that underpin these applications resulting in 2D hBN layers that could be integrated into devices where diamonds can’t be.
Scientists have characterized this material and found several unusual and fascinating features, but research on hBN is still in its infancy.
Co-lead author Dominic Scognamiglio says, “There are no other publications on charge state switching, manipulation or stability of boron vacancies, which is why we’re taking the first step in filling this literature gap and understanding this material better.”
Chief Investigator Milos Toth says, “The next phase of this research will focus on pump-probe measurements that will allow us to optimize defects in hBN for applications in sensing and integrated quantum photonics.”
Scientists developed a new experimental setup that combined a confocal photoluminescent microscope with a scanning electron microscope (SEM) to analyze the boron vacancy defects in hBN. As a result, they were able to measure the defect and control the charge states of boron vacancy defects using an electron beam and electrical microcircuits.
Co-lead author Angus Gale says, “The approach is novel. It allows us to focus the laser onto individual image defects in hBN while they are manipulated using electronic circuits and an electron beam. This modification to the microscope is unique; it was incredibly useful and streamlined our workflow significantly.”
Journal Reference:
- Angus Gale, Dominic Scognamiglio, Ivan Zhigulin, Benjamin Whitefield, Mehran Kianinia, Igor Aharonovich, and Milos Toth. Manipulating the Charge State of Spin Defects in Hexagonal Boron Nitride. Nano Letters. DOI: 10.1021/acs.nanolett.3c01678