Scanning electron microscope images of the suspended structures of single crystal diamond, (a) cantilever, (b) bridge, and (c) 3-terminal NEMS switch.
Air gap structure has been formed in the substrate side.
Dr. Meiyong Liao, a Senior Researcher of Sensor Materials Center, National Institute for Materials Science (Japan), and his colleagues, succeeded in the batch fabrication of suspended structures (cantilevers and bridges) of single crystal diamond for nano/micro electromechanical system (NEMS/MEMS). Based on this process, they achieved in the world the first single crystal diamond NEMS switch.
In comparison with the existing MEMS switches, the diamond NEMS switches are expected to show greatly improved functions, including reliability, lifetime, speed, and electrical handling capacity, etc. The developed devices can be applied as microwave switch for next-generation wireless communications and logic circuit under harsh environments. These research results also establish the infrastructure for diamond NEMS/MEMS with novel functions, opening the way for the development of various chemical, physical, and mechanical sensors.
The leakage current of the developed diamond NEMS switch is very low, and the power consumption is less than 10pW (picowatt). The devices exhibit high reproducibility, high reliability and no surface stiction. Stable operation of the diamond NEMS switch in a high temperature environment (250°C) was also confirmed. The Young’s modulus of the moveable cantilever structure was measured to be 1100GPa, which is close to the value of bulk diamond single crystals. Thus, high-speed (gigahertz) switching operation can be expected.
The NIMS research team developed a process for fabricating suspended single crystal diamond structures by locally forming a graphite sacrificial layer in a single crystal diamond substrate by high energy ion implantation, followed by the growth of a diamond epilayer with electrical conductivity by microwave plasma chemical vapor deposition method (MPCVD) and the removal of the graphite sacrificial layer. As a further development of this technique, the group also succeeded for the first time in fabricating NEMS switching devices with a transistor-like structure comprising 3 electrodes.
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