Residual Stress Distribution, Intermolecular Force, And Frictional Coefficient Maps In Diamond Films: Processing-Structure-Mechanical Property Relationship

Abstract

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 21st Century. In order to utilize effectively these materials for M/NEMS applications, understanding of their microscopic structure and physical properties (mechanical, in particular) become indispensable. The micro-and nanocrystalline diamond films were grown using hotfilament 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 the 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, while 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.