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Introduction Chemical vapor deposition (CVD) diamond film technology has experienced modest growth in the last two decades in terms of scientific and technological advances in the field, which has, ultimately, positively affected progress in diamondbased microelectromechanical/nanoelectromechanical systems (MEMS/NEMS). In the early 1990s, soon after realizing excellent mechanical, chemical, electrical, and optical properties of polycrystalline diamond films, which attracted attention from the MEMS community, the initial challenges ranged from mostly dealing with the rough microcrystalline morphology and developing surface micromachining processing techniques to the fabrication of basic MEMS structures (e.g., cantilever, bridges, comb-drive)1,2 and characterization of mechanical properties such as Young’s modulus, intrinsic stress, and fracture strength. Soon after the introduction of nanocrystalline (NCD) and ultrananocrystalline diamond (UNCD) thin-film technology in the late 1990s, demonstrating mechanical and tribological properties close to that of single crystal diamond (SCD),3 interest peaked in this area. Multiple groups worked from all over the world, leading to rapid progress in this field in recent years. Although in terms of optimizing residual stress (stress management), diamond thin-films are still not there yet as

compared to silicon, it is now possible to control the residual stress in diamond films to a certain extent to fabricate “all diamond” moving MEMS devices with reasonable complexity.4 Surface micromachining technology in diamond is now well matured, and advanced NEMS devices even in SCD have been demonstrated.5,6 Integration of diamond with piezoelectric materials such as PZT7 and AlN8 added another boost, enabling fabrication of high-performance piezoelectric-driven MEMS/NEMS. The first demonstration of complementary metal oxide semiconductor (CMOS) compatibility of UNCD9 and thereafter fabrication of a radio frequency MEMS switch using UNCD as a dielectric layer driven by on-chip CMOS at wafer-scale10 was a major step forward in diamond MEMS technology, paving the entry of diamond MEMS in communications electronics. Researchers are now successful in locating and manipulating electron spin associated with nitrogen-vacancy (NV) centers in diamond (substituted nitrogen atom in the diamond lattice paired with a nearest-neighbor vacancy) by applying external stimuli such as an electric field, magnetic field, microwave radiation or light, or a combination. This could be utilized to develop ultrasensitive NEMS sensors that can detect very weak magnetic fields (∼few nano tesla)11 useful for biomedical imaging.12 The NV centers are also considered a basic

Anirudha V. Sumant, Argonne National Laboratory, IL, USA; [email protected] Orlando Auciello, University of Texas at Dallas, USA; [email protected] Meiyong Liao, National Institute for Materials Science, Japan; [email protected] Oliver A. Williams, School of Physics and Astronomy, Cardiff University, UK; [email protected] DOI: 10.1557/mrs.2014