Quantum sensing for 2D materials
What are 2D Materials?
2D materials are materials that are made up of a single layer of atoms or molecules. They are incredibly thin, with a thickness that is only one or a few atoms thick. These materials have unique properties that are not found in their bulk counterparts, such as exceptional strength, flexibility, and electrical conductivity. Some examples of 2D materials include graphene, which is made up of carbon atoms arranged in a hexagonal lattice, and molybdenum disulfide (MoS2), which consists of layers of molybdenum atoms sandwiched between layers of sulfur atoms. Because of their unique properties, 2D materials have a wide range of potential applications in electronics, energy, and other fields. MoS₂ have magneto-optical responses ideally suited for electronic devices which may enhance performance in transmitting data on and between computer chips. Graphene is one of the most established 2D materials, and its unique properties have been leveraged into many applications, particularly in the biomedical sector where from wearable technology to membranes they can make huge impacts. 2D materials are also revolutionizing many fields by making applications possible that were previously only theoretical, such as quantum computing. They have the potential to not only create artificial states of quantum matter but also fulfill a range of promises in solid-state quantum computing. They can serve as crucial components in quantum communication circuits and enable intriguing quantum sensing schemes.
The advantages of quantum sensing
As materials get thinner and smaller, the signal they generate is small. Therefore it is increasingly critical to have both high resolution and high sensitivity to do research and development into understanding them. Their magnetic and electric properties are often the most interesting. Magnetic fields also do not have the same optical penetration limits as optical methods. There are different commercially available sensors to characterize materials, each with their own strengths and weaknesses and unique niche. Diamond-based quantum sensing however is a measurement tool with very unique capabilities. Users can probe material on very small length scales across a large temperature range with high sensitivity. NV-centers as quantum sensors in diamonds are also becoming commercially available.
There are two state-of-the-art methods that are relevant to industrial applications: Scanning tip and wide-field imaging. For the scanning tip method, an NV diamond tip is moved pixel by pixel over the sample. This technique enables a very high spatial resolution (25 - 50 nm) that few techniques can match. However, scanning is costly. A single diamond tip costs thousands of euros and would need to be replaced regularly. The application potential of the scanning tip approach is limited by its long measurement time, as it takes more than 3 hours to measure less than 100 square microns. Wide-field imaging records the fluorescence of a diamond with a camera, simultaneously measuring and spatially correlating the signal recorded by each pixel. The approach meets the high speed required by many industrial applications and has a field of view of a few square millimeters (typically limited by the size of the diamond). However, its spatial resolution is at best a tenth (350 - 500 nm) of the scanning tip method, limiting its applicability for most industrial use cases.
The fundamentals of research
Industrial use cases as previously mentioned are mainly in the realm of applied research. However, fundamental research is also crucial to be engaged with, the reason being that it is fundamental science that leads to breakthroughs in capabilities such as microscopy, which will lead to new science and technological advances. NV-diamonds are ready to make an impact in studying materials and devices! Wide-field imaging at the moment is cheaper and more accessible. Positioning diamond “microchips” of roughly 10 to 50 microns on the material would reduce dust and surface inhomogeneity as well as optical aberrations. One example of such fundamental research was done at Harvard by Ku et al.. In this study, the researchers used quantum spin magnetometers to directly image viscous Dirac fluid flow in graphene at room temperature by measuring the associated stray magnetic field. The results showed a parabolic Poiseuille profile for electron flow in a high-mobility graphene channel near the charge-neutrality point, indicating the viscous transport of the Dirac fluid. This measurement contrasted with the conventional uniform flow profile seen in metallic conductors and low-mobility graphene channels. This work also highlights the potential of quantum spin magnetometers to probe such materials and phenomena at the nanoscale. Work such as this will push forward the global market of approximately $ 2 billion dollars to be closer to $ 3 billion even as soon as 2027!