Ultra-High Quality Diamond Cantilevers-Based MEMS Sensor Chip

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Researchers from National Institute for Materials Science, Japan developed a single crystal diamond microelectromechanical systems sensor chip

A team of researchers from National Institute for Materials Science (NIMS), Japan developed a high-quality diamond cantilever with the highest quality (Q) factor values at room temperature. Moreover, the team also succeeded in developing a single crystal diamond microelectromechanical systems (MEMS) sensor chip capable of actuating and sensing through electrical signals. According to the researchers, the findings can facilitate development of research on diamond MEMS with significantly higher sensitivity and greater reliability as compared to current silicon MEMS. The research was published in the journal Physical Review Materials on September 28, 2018.

Microscopic cantilevers that project beams at only one end and electronic circuits are integrated on a single substrate in MEMS sensors. These sensors are used in gas sensors, mass analyzers, and scanning microscope probes. Increase in sensitivity and reliability of MEMS sensors can boost application of these sensors in a wider variety of fields such as disaster prevention and medicine. Diamond has the highest elastic constant and mechanical constant, which makes it promising for use in the development of highly reliable and sensitive MEMS sensors. However, three-dimensional microfabrication of diamond is challenging due to its mechanical hardness.  In 2010, the team developed a ‘smart cut’ fabrication method that allows microprocessing of diamond with the help of ion beams. This allowed the team to fabricate a single crystal diamond cantilever. However, the quality factor of the diamond cantilever was equivalent to currently used silicon cantilevers due to the presence of surface defects.

The team developed a new technique that allowed atomic-scale etching of diamond surfaces. The etching technique enabled to remove defects on the bottom surface of the single crystal diamond cantilever. The team found that the resulting cantilever exhibited Q factor values greater than one million. Q factor is a parameter used to measure the sensitivity of a cantilever. The team formulated a novel MEMS device concept that described simultaneous integration of a cantilever. The device is an electronic circuit that oscillates the cantilever and an electronic circuit that senses the vibration of the cantilever. The team later developed a single crystal diamond MEMS chip capable of actuating with the help of electrical signals.

Rina Vidyasagar

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