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J9.2.1

Mechanical Properties of Ultrananocrystalline Diamond Thin Films for MEMS Applications H.D. Espinosa1, B. Peng1, K.-H. Kim1, B.C. Prorok2, N. Moldovan3, X.C. Xiao3, J.E. Gerbi3, J. Birrell3, O. Auciello3, J.A. Carlisle3, D.M. Gruen3, and D.C. Mancini3 1

2 3

Department of Mechanical Engineering, Northwestern University Evanston, IL 60208-3111, USA Materials Research and Education Center, Auburn University, Auburn, AL 36849-5341, USA Materials Science and Experimental Facilities Divisions, Argonne National Laboratory Argonne, IL 60439, USA

ABSTRACT Microcantilever deflection and the membrane deflection experiment (MDE) were used to examine the elastic and fracture properties of ultrananocrystalline diamond (UNCD) thin films in relation to their application to microelectromechanical systems (MEMS). Freestanding microcantilevers and membranes were fabricated using standard MEMS fabrication techniques adapted to our UNCD film technology. Elastic moduli measured by both methods described above are in agreement, with the values being in the range 930 and 970 GPa with both techniques showing good reproducibility. The MDE test showed fracture strength to vary from 3.95 to 5.03 GPa when seeding was performed with ultrasonic agitation of nanosized particles. INTRODUCTION Carbon in its various forms, specifically diamond, may become a key material for the manufacturing of MEMS/NEMS devices in the 21st Century. The new ultrananocrystalline diamond (UNCD) films developed at Argonne National Laboratory [1] may provide the basis for revolutionary microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). The UNCD films are grown using a microwave plasma chemical vapor deposition technique involving a novel CH4/Ar chemistry. The process yields films with extremely small grain size (2-5 nm), significantly smaller than nanocrystalline diamond films (30-100 nm grain size) produced by the conventional CH4/H chemistry [2,3]. The UNCD films posses many of the outstanding physical properties of diamond, i.e., they exhibit exceptional hardness, extremely low friction coefficient and wear, high thermal and electrical conductivity, the latter when doped with nitrogen [4]. Preliminary results have shown that this unique microstructure results in outstanding mechanical properties (~ 97 GPa hardness and 967 GPa Young’s modulus that are similar to single crystal diamond [5]), unique tribological properties (coefficient of friction of the order of ~0.02-0.03, [6]), and field-induced electron emission (threshold voltage 2-3 V/µm, [7]). Preliminary work by investigators at Argonne has demonstrated the feasibility of fabricating 2-D and 3-D MEMS components that can be the basis for the fabrication of complete MEMS / NEMS devices [8-10]. Components such as cantilevers and multi-level devices such as microturbines have already been produced. These preliminary exercises are promising steps toward full-scale application of UNCD components in functional MEMS devices. However, before full-scale integration can occur, several