Are you curious to know how NV centers were turned into nanoscale sensors? When did it happen and how did it start? Well, you are in the right spot. This week, we will uncover the rather brief, but pretty intense history of Nitrogen-Vacancy probes. From the first proof of concept to the first commercial probe developed by Qnami and beyond.
Are you ready to discover the path that brought us where we are now?
Let’s dive in
NV centers are naturally extremely powerful sensors. When a single NV center is scanned over a surface, a wide range of applications can be unlocked: from electrical and magnetic-field sensing to quantum information processing, and bioimaging.
The first successful attempt to use NV centers as scanning probes was made in 2008 by Balasubramanian et al in Stuttgart. The team grafted nanodiamonds onto a scanning probe tip and used it to map nanoscale magnetic field variations. The achieved sensing performances were however limited by the short spin coherence time of NVs in nanodiamonds, and the inefficient collection of fluorescence light.
Back in 2012 – The first all-diamond tip
The beginning of the revolution of the NV probes was marked in 2012 at Harvard. Maletinsky et al radically changed the approach by placing a single NV center at the apex of a high-purity all-diamond nanopillar used as the tip of an atomic force microscope.
This resulted in a more robust NV probe with NVs preserving very long spin coherence times, and record-high signal collection efficiencies. A new era for high-sensitivity and high-spatial resolution Scanning NV Magnetometry began. The first sample characterized with the first ever monolithic scanning NV sensor was a magnetic memoryd device.
Peer-reviewed results: Nature Nanotechnology volume 7, pages320–324 (2012)
Back in 2016 – 2017 – Scalability and first commercial probes
After intense work on optimizing complex fabrication processes, in 2016 Appel et al at the University of Basel published a paper describing an advanced procedure for producing robust all-diamond scanning probes starting from commercially available diamond material. The team presented a a scalable procedure suited for structuring large volumes. The team led by Prof. Maletinsky, used the probes to image the dipolar field of Nickel nanorods.
Few months later, Qnami joined forces with the Quantum Sensing Lab at the University of Basel and the Paul Sherrer Institute and won the Nano Argovia grant. With the grant they initiated the NQsense project to boost even further the sensitivity of scanning NV probes. The project ensured the technology transfer from the University of Basel to Qnami and led to the first commercial scanning NV probe DP-Quant1. Qnami sold the first DP-Quant1 unit already in 2018.
Since 2019 – Second generation and first scientific results
After the beginning of the commercialization in 2017-2018, Qnami continued the development of scanning NV probes to push the performances to the optimal limits. In 2019, the second generation of Qnami diamond tips, Quantilever MX, was launched. The performance of this new generation was drastically improved by otpimizing the geometry of the pillar from cylindrical as in DP-Quant1, to tapered.
Since 2019, the Quantilever MX probes unlock a wide range of applications: from the first demonstration of new chiral spin-textures occurring on BiFeO3’s domain-walls, to stable skyrmions in exchage-biased ultra thin films imaged at room temperature, or imaging non collinear spin textures through magnetic noise. We are extremely happy to see that the list goes on and on.