Residual stress, intermolecular force, and frictional properties distribution maps of diamond films for micro- and nano-
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O.A. Williams Institute for Materials Research, Universiteit Hasselt, BE-3590 Diepenbeek, Belgium
R.J. Patel Department of Physics and Materials Science, Missouri State University, Springfield, Missouri 65897
K. Haenen Institute for Materials Research, Universiteit Hasselt, BE-3590 Diepenbeek, Belgium (Received 11 May 2006; accepted 3 August 2006)
Carbon in its various forms, specifically nanocrystalline diamond, may become a key material for the manufacturing of micro- and nano-electromechanical (M/NEMS) devices in the twenty-first century. To utilize effectively these materials for M/NEMS applications, understanding of their microscopic structure and physical properties (mechanical properties, in particular) become indispensable. The microcrystalline and nanocrystalline diamond films were grown using hot-filament and microwave chemical vapor deposition techniques involving novel CH4/[TMB for boron doping and H2S for sulfur incorporation] in high hydrogen dilution chemistry. To investigate residual stress distribution and intermolecular forces at nanoscale, the films were characterized using Raman spectroscopy and atomic force microscopy in terms of topography, force curves, and force volume imaging. Traditional force curve measures the force felt by the tip as it approaches and retracts from a point on the sample surface, whereas force volume is an array of force curves over an extended range of sample area. Moreover, detailed microscale structural studies are able to demonstrate that the carbon bonding configuration (sp2 versus sp3 hybridization) and surface chemical termination in both the un-doped and doped diamond have a strong effect on nanoscale intermolecular forces. The preliminary information in the force volume measurement was decoupled from topographic data to offer new insights into the materials’ surface and mechanical properties of diamond films. These measurements are also complemented with scanning electron microscopy and x-ray diffraction to reveal their morphology and structure and frictional properties, albeit qualitative using lateral force microscopy mode. We present these comparative results and discuss their potential impact for electronic and electromechanical applications.
I. INTRODUCTION
Diamond is a promising wide-gap semiconductor material with a large potential offering excitement and interest due to its unique blend of superlative physical (electronic, optical, mechanical, and chemical) properties.1,2 Diamond thin film (DTF) are attractive for several applications such as in tribological coatings and cutting a)
Address all correspondence to this author. Present address: Univ. of Missouri, ECE Department, Columbia, MO 65211-2300. e-mail: [email protected] DOI: 10.1557/JMR.2006.0372 J. Mater. Res., Vol. 21, No. 12, Dec 2006
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tools (extreme hardness), heat sinks3,4 (high thermal conductivity), optical windows (wide band gap, 5.45 eV)5 (wide spectral transparency), high temperature and high power electronics (breakdown volta
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