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Register a new userDiamond spin sensors: A new way to probe nanomagnetism
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Studies of individual quantum systems, which have led to considerable progress in our understanding of quantum physics, have traditionally been associated with atomic gases. In the last decades however, the emphasis has shifted towards solid-state systems, which are much more practical for applications. In particular, a new field has recently emerged that is concerned with the study of quantum systems based on single spins localized near point defects in crystalline solids. One such system is the nitrogen-vacancy (NV) defect in diamond. Initially used as an experimental breadboard for testing concepts of quantum physics and quantum computation, the NV defect was soon proposed as a sensitive magnetometer, capable of detecting minute magnetic fields, down to ultimate level of single spins. This atomic-sized magnetometer can be used as a standalone sensor, or integrated into an imaging system providing spatial resolution down to the atomic scale. Diamond-based instruments thus offer new pathways to probe the magnetism of matter from the mesoscale down to the nanoscale. This book chapter gives an overview of the field of diamond-based magnetic sensing and imaging, with an emphasis on already demonstrated applications of this technology. The chapter is divided into three main sections. In Section 2, the underlying physics and methods of diamond-based magnetometry are described. Section 3 is devoted to various experimental implementations that employ this new class of sensors for magnetic sensing and imaging. Finally, some recent applications are presented in Section 4.
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Atomic-size spin defects in solids are unique quantum systems. Most applications require nanometer positioning accuracy, which is typically achieved by low energy ion implantation. So far, a drawback of this technique is the significant residual implantation-induced damage to the lattice, which strongly degrades the performance of spins in quantum applications. In this letter we show that the charge state of implantation-induced defects drastically influences the formation of lattice defects during thermal annealing. We demonstrate that charging of vacancies localized at e.g. individual nitrogen implantation sites suppresses the formation of vacancy complexes, resulting in a tenfold-improved spin coherence time of single nitrogen-vacancy (NV) centers in diamond. This has been achieved by confining implantation defects into the space charge layer of free carriers generated by a nanometer-thin boron-doped diamond structure. Besides, a twofold-improved yield of formation of NV centers is observed. By combining these results with numerical calculations, we arrive at a quantitative understanding of the formation and dynamics of the implanted spin defects. The presented results pave the way for improved engineering of diamond spin defect quantum devices and other solid-state quantum systems.
The precise measurement of mechanical stress at the nanoscale is of fundamental and technological importance. In principle, all six independent variables of the stress tensor, which describe the direction and magnitude of compression/tension and shear stress in a solid, can be exploited to tune or enhance the properties of materials and devices. However, existing techniques to probe the local stress are generally incapable of measuring the entire stress tensor. Here, we make use of an ensemble of atomic-sized in-situ strain sensors in diamond (nitrogen-vacancy defects) to achieve spatial mapping of the full stress tensor, with a sub-micrometer spatial resolution and a sensitivity of the order of 1 MPa (corresponding to a strain of less than $10^{-6}$). To illustrate the effectiveness and versatility of the technique, we apply it to a broad range of experimental situations, including mapping the elastic stress induced by localized implantation damage, nano-indents and scratches. In addition, we observe surprisingly large stress contributions from functional electronic devices fabricated on the diamond, and also demonstrate sensitivity to deformations of materials in contact with the diamond. Our technique could enable in-situ measurements of the mechanical response of diamond nanostructures under various stimuli, with potential applications in strain engineering for diamond-based quantum technologies and in nanomechanical sensing for on-chip mass spectroscopy.
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