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Title: Amorphous Diamond MEMS and Sensors

Abstract

This report describes a new microsystems technology for the creation of microsensors and microelectromechanical systems (MEMS) using stress-free amorphous diamond (aD) films. Stress-free aD is a new material that has mechanical properties close to that of crystalline diamond, and the material is particularly promising for the development of high sensitivity microsensors and rugged and reliable MEMS. Some of the unique properties of aD include the ability to easily tailor film stress from compressive to slightly tensile, hardness and stiffness 80-90% that of crystalline diamond, very high wear resistance, a hydrophobic surface, extreme chemical inertness, chemical compatibility with silicon, controllable electrical conductivity from insulating to conducting, and biocompatibility. A variety of MEMS structures were fabricated from this material and evaluated. These structures included electrostatically-actuated comb drives, micro-tensile test structures, singly- and doubly-clamped beams, and friction and wear test structures. It was found that surface micromachined MEMS could be fabricated in this material easily and that the hydrophobic surface of the film enabled the release of structures without the need for special drying procedures or the use of applied hydrophobic coatings. Measurements using these structures revealed that aD has a Young's modulus of {approx}650 GPa, a tensile fracture strength of 8 GPa,more » and a fracture toughness of 8 MPa{center_dot}m {sup 1/2}. These results suggest that this material may be suitable in applications where stiction or wear is an issue. Flexural plate wave (FPW) microsensors were also fabricated from aD. These devices use membranes of aD as thin as {approx}100 nm. The performance of the aD FPW sensors was evaluated for the detection of volatile organic compounds using ethyl cellulose as the sensor coating. For comparable membrane thicknesses, the aD sensors showed better performance than silicon nitride based sensors. Greater than one order of magnitude increase in chemical sensitivity is expected through the use of ultra-thin aD membranes in the FPW sensor. The discoveries and development of the aD microsystems technology that were made in this project have led to new research projects in the areas of aD bioMEMS and aD radio frequency MEMS.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
800990
Report Number(s):
SAND2002-1755
TRN: US200224%%160
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 2002
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; AMORPHOUS STATE; DIAMONDS; ELECTRIC CONDUCTIVITY; FRACTURE PROPERTIES; MECHANICAL PROPERTIES; MEMBRANES; ORGANIC COMPOUNDS; SENSITIVITY; SILICON NITRIDES; WEAR RESISTANCE; MINIATURIZATION; MICROELECTRONICS

Citation Formats

SULLIVAN, JOHN P., FRIEDMANN, THOMAS A., ASHBY, CAROL I., DE BOER, MAARTEN P., SCHUBERT, W. KENT, SHUL, RANDY J., HOHLFELDER, ROBERT J., and LAVAN, D.A. Amorphous Diamond MEMS and Sensors. United States: N. p., 2002. Web. doi:10.2172/800990.
SULLIVAN, JOHN P., FRIEDMANN, THOMAS A., ASHBY, CAROL I., DE BOER, MAARTEN P., SCHUBERT, W. KENT, SHUL, RANDY J., HOHLFELDER, ROBERT J., & LAVAN, D.A. Amorphous Diamond MEMS and Sensors. United States. doi:10.2172/800990.
SULLIVAN, JOHN P., FRIEDMANN, THOMAS A., ASHBY, CAROL I., DE BOER, MAARTEN P., SCHUBERT, W. KENT, SHUL, RANDY J., HOHLFELDER, ROBERT J., and LAVAN, D.A. Sat . "Amorphous Diamond MEMS and Sensors". United States. doi:10.2172/800990. https://www.osti.gov/servlets/purl/800990.
@article{osti_800990,
title = {Amorphous Diamond MEMS and Sensors},
author = {SULLIVAN, JOHN P. and FRIEDMANN, THOMAS A. and ASHBY, CAROL I. and DE BOER, MAARTEN P. and SCHUBERT, W. KENT and SHUL, RANDY J. and HOHLFELDER, ROBERT J. and LAVAN, D.A.},
abstractNote = {This report describes a new microsystems technology for the creation of microsensors and microelectromechanical systems (MEMS) using stress-free amorphous diamond (aD) films. Stress-free aD is a new material that has mechanical properties close to that of crystalline diamond, and the material is particularly promising for the development of high sensitivity microsensors and rugged and reliable MEMS. Some of the unique properties of aD include the ability to easily tailor film stress from compressive to slightly tensile, hardness and stiffness 80-90% that of crystalline diamond, very high wear resistance, a hydrophobic surface, extreme chemical inertness, chemical compatibility with silicon, controllable electrical conductivity from insulating to conducting, and biocompatibility. A variety of MEMS structures were fabricated from this material and evaluated. These structures included electrostatically-actuated comb drives, micro-tensile test structures, singly- and doubly-clamped beams, and friction and wear test structures. It was found that surface micromachined MEMS could be fabricated in this material easily and that the hydrophobic surface of the film enabled the release of structures without the need for special drying procedures or the use of applied hydrophobic coatings. Measurements using these structures revealed that aD has a Young's modulus of {approx}650 GPa, a tensile fracture strength of 8 GPa, and a fracture toughness of 8 MPa{center_dot}m {sup 1/2}. These results suggest that this material may be suitable in applications where stiction or wear is an issue. Flexural plate wave (FPW) microsensors were also fabricated from aD. These devices use membranes of aD as thin as {approx}100 nm. The performance of the aD FPW sensors was evaluated for the detection of volatile organic compounds using ethyl cellulose as the sensor coating. For comparable membrane thicknesses, the aD sensors showed better performance than silicon nitride based sensors. Greater than one order of magnitude increase in chemical sensitivity is expected through the use of ultra-thin aD membranes in the FPW sensor. The discoveries and development of the aD microsystems technology that were made in this project have led to new research projects in the areas of aD bioMEMS and aD radio frequency MEMS.},
doi = {10.2172/800990},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Jun 01 00:00:00 EDT 2002},
month = {Sat Jun 01 00:00:00 EDT 2002}
}

Technical Report:

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  • The state-of-the-art of inertial micro-sensors (gyroscopes and accelerometers) has advanced to the point where they are displacing the more traditional sensors in many size, power, and/or cost-sensitive applications. A factor limiting the range of application of inertial micro-sensors has been their relatively poor bias stability. The incorporation of an integral sensitive axis rotation capability would enable bias mitigation through proven techniques such as indexing, and foster the use of inertial micro-sensors in more accuracy-sensitive applications. Fabricating the integral rotation mechanism in MEMS technology would minimize the penalties associated with incorporation of this capability, and preserve the inherent advantages of inertialmore » micro-sensors.« less
  • The objective of this project was to determine why diamond-based films are unusually efficient electron emitters (field emission cathodes) at room temperature. Efficient cathodes based on diamond are being developed by SI Diamond Technology (SIDT) as components for bright, sunlight-readable, flat panel displays. When the project started, it was known that only a small fraction (<1%) of the cathode area is active in electron emission and that the emission sites themselves are sub-micron in size. The critical challenge of this project was to develop new microcharacterization methods capable of examining known emission sites. The research team used a combination ofmore » cathode emission imaging (developed at SIDT), micro-Raman spectroscopy (LBNL), and electron microscopy and spectroscopy (National Center for Electron Microscopy, LBNL) to examine the properties of known emission sites. The most significant accomplishment of the project was the development at LBNL of a very high resolution scanning probe that, for the first time, measured simultaneously the topography and electrical characteristics of single emission sites. The increased understanding of the emission mechanism helped SIDT to develop a new cathode material,''nano-diamond,'' which they have incorporated into their Field Emission Picture Element (FEPix) product. SIDT is developing large-format flat panel displays based on these picture elements that will be brighter and more efficient than existing outdoor displays such as Jumbotrons. The energy saving that will be realized if field emission displays are introduced commercially is in line with the energy conservation mission of DOE. The unique characterization tools developed in this project (particularly the new scanning microscopy method) are being used in ongoing BES-funded basic research.« less
  • Los Alamos National Laboratory has developed diamond sensors with interdigitated electrodes that operate in a photoconducting mode. The specific application for this work was for the Department of Energy`s instruments flown on the Global Positioning System satellites. Sensors have been fabricated and tested for their response to low-energy x-rays. These sensors can be operated to extremely high volumetric radiation doses. We find that the sensors are extremely useful for situations where the surface radiation dose is not excessive, but that this limit is exceeded for the GPS orbit. It is possible that further studies and special detector arrangements or auxiliarymore » heating of the sensor may push this limit to higher values.« less
  • In order to safeguard the silicon vertex tracker in the BaBar detector from excessive radiation damage, cumulative dose and instantaneous dose rates are continuously monitored. As an upgrade to the current radiation monitoring system which uses silicon PIN-diodes, we are examining the possible use of single-crystal and/or polycrystalline chemical vapor deposition (CVD) diamonds. The radiation responses of several CVD diamonds have been tested on time scales from tens of nanoseconds to thousands of seconds in order to determine their integrity in monitoring accumulated dose and their response to large sudden changes in dose rates. Two polycrystalline CVD diamonds have beenmore » installed near the silicon vertex tracker near existing silicon PIN-diodes for comparative studies. CVD diamond radiation sensors have also been tested using {sup 60}Co and in various magnetic field configurations.« less