Call It Scanning NV Microscopy: More Than Magnetic Field Images

Even though scanning Nitrogen Vacancy microscopy (SNVM) was only invented 15 years ago, both first proposals and first implementation date to 2008, one can already speak of the “historical” application, which is magnetometry. A single nitrogen vacancy center (NV) at the tip of a scanning probe acts as an atomic size quantum sensor, yielding quantitative data with high sensitivity at the nanometer scale and in a wide range of conditions, from ambient to vacuum, from room temperature to sub-Kelvin.

Mainly, this data has been the magnetic stray field projected on the NV axis. A number of key factors has made scanning NV especially attractive for magnetometry at the nanometer scale: 1. The high sensitivity, down to 1.1 µT/ÖHz in cw ODMR for top-of-the-line QZabre scanning tips in our scanning NV system. 2 The high spatial resolution of better than 50 nm. 3. The NV does not create any back-action. These notable features have contributed to high profile scientific studies of, amongst others, anti ferromagnets, multi-ferroics and 2D magnets, all with rich physics and all high-profile candidates for advanced non-volatile fast memories or beyond CMOS devices.

Quantitative images of stray fields are very useful, but are only one of several ways that scanning NV can be used. Staying in the realm of magnetic fields, the QSM can now measure hysteresis loops, a staple of magnetic characterization methods, but now feasible at the nm scale. In combination with Quickscan, Qzabre’s fast mode that provides fully quantitative real time data at up to 200 pixels/s, you can choose between single points on your sample, a grid of points, or even images.

Ferromagnetic Resonance measurements are another classic method of material characterization that NV technology has now moved from the millimeter scale to the nanometer scale. Whether it is plain characterization at a different size scale or probing inhomogeneities, SNVM will help you understand your material better.

While tracking currents and measuring current densities is technically magnetometry, the spatial resolution is on the order of the current metal line spacing in today’s 5 nm node. The novel possibility of tracing signals in a running chip creates applications such as failure analysis and design verification for security sensitive applications.

Wrapping up, Qzabre recently implemented a new sensing protocol called gradiometry. For magnetic field, this protocol increases sensitivity by almost a factor of 10. This means high quality images of sub-µT fields are now possible without needing days of integration time. More important, one can also measure electric fields with this protocol, for example the field distribution between MEMS electrodes. In summary, SNVM can provide so much more data than just quantitative maps of magnetic stray fields. Get in touch with Qzabre if they have raised your interest!

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