GOALI: Stable Nanomechanical Oscillators with Large f*Q Product

Harvard University, Cambridge MA

Investigators

Abstract

'1. Proposal Title: GOALI: Stable Nanomechanical Oscillators with Large f*Q Product 2. Brief description of project Goals: Nanoscale electro-opto-mechanical systems will be fabricated in diamond, and their applications in precision measurements (e.g. mass, force) will be explored. 3. Abstract: a) Nontechnical Abstract: Diamond is a fascinating material with many remarkable properties. In fact, in many ways it is the ultimate engineering material - the engineer's best friend! For example, diamond has high mechanical hardness and is one of the best thermal conductors. It is optically transparent from the ultra-violet to far infra-red and has a high refractive index (n = 2.4). Finally, it is biocompatible and chemically inert. These properties make diamond a highly desirable material for many applications, including those in life sciences, oil discovery, and industrial sensing. Many of these applications require realization of high-frequency (f), high quality factor (Q), stable, nanoscale electro-mechanical and opto-mechanical systems (NEMS and NOMS). These systems could lead to realization of stable oscillators and sensitive mass measurements, and could operate in both harsh environments (due to diamond's chemical inertness) and in bio-medical setting (due to diamond's bio-compatibility). Despite its unique properties, however, single-crystal diamond has not found many applications in NEMS and NOMS yet! Why? All NEMS/ NOMS platforms have an important feature in common: they consist of a device layer typically a thin film supported by a substrate of a different material that can be sacrificially removed. Single-crystal diamond is one example from an extensive list of materials many with attractive material properties for which such thin film platform does not exist. To overcome this obstacle, the team will leverage angled-etching fabrication technique (pioneered by Loncar group) that allows for realization of functional devices in bulk diamond substrates, and state of the art materials and material expertise provided by industrial partner (Element 6). b) Technical Abstract: The goal of the proposed experimental program is to investigate the potential of single crystal diamond as a NEMS/ NOMS material. The program will address many fundamental questions that pertain to crystalline NEMS, including material synthesis, nanofabrication, performance limits, and so on. In particular, potential for realization of high f*Q product mechanical oscillators in diamond and their applications in precision measurements (mass, force) and as a stable timing reference will be explored. This will be accomplished using angled-etching technique to realize cantilevers, contour resonators, acoustic-wave whispering gallery mode resonators, and optomechanical crystals (photonic-phononic lattices) in single crystal diamond substrates. Angled-etching technique, recently demonstrated by Harvard team, is based on a combination of top-down etching, where ions in the RIE chamber impinge vertically on the diamond surface, with subsequent angled etching, where ions are directed at an angle on the etched features. In the later etch step, the sample is inserted in a Faraday cage, whose geometry defines the angle of incidence of ions on the etched substrate. Collaboration between academic research lab and industrial partner is mutually beneficial: industrial partner (Element Six) will provide state-of-the-art diamond substrates, bulk diamond processing (including polishing and annealing), and when appropriate support commercial development; on the other hand, Harvard team will provide insight into cutting edge NEMS and NOMS research, and develop novel nanofabrication and characterization techniques of interest to industry. The program has strong theoretical and experimental component, addresses both fundamental and engineering aspects of nanoscale mechanics and optics, and represents a unique research and educational opportunity for undergraduate, graduate and post-graduate students. Collaboration with industrial partner will enable internship opportunities for students. The team will continue giving public lectures at local schools and Museum of Science (Boston), and mentoring high school students interested in science and technology.