ABSTRACT
Abstract .................................................................................................................. 104 5.1Introduction .................................................................................................. 104 5.2Materials and Methods ................................................................................. 105
5.2.1Materials ........................................................................................... 105 5.2.2SAM Formation ................................................................................ 105 5.2.3 Transmission FTIR ........................................................................... 105 5.2.4Contact Angle Measurement ............................................................ 106 5.2.5Atomic Force Microscopy ................................................................ 106
5.3Results ........................................................................................................... 106 5.3.1Temperature Effects on Molecular Packing in SAM Films ............. 106 5.3.2 Surface Energy of SAM-Modi”ed Silicon as a Function of
Temperature ...................................................................................... 109 5.3.3Temperature Effect on Surface Topography ..................................... 110 5.3.4Temperature Effect on Surface Friction ........................................... 112
5.4Discussion ..................................................................................................... 114 5.4.1 Temperature Effects on Molecular Packing State and
Nanotribological Properties of SAMs .............................................. 114 5.5Conclusion .................................................................................................... 115 Acknowledgments .................................................................................................. 116 References .............................................................................................................. 116
Self-assembled monolayers (SAMs) are promising candidates for lubrication ”lmsinmicro-andnanoelectromechanicalsystems(MEMSandNEMS) devices.Characterizingchangesinthestructureandstabilityofthese”lms duetothermalcyclingisimportantforoptimizingtheirperformance.Inthis report,wehaveusedhexyltrichlorosilane(C6),dodecyltrichlorosilane(C12), and octadecyltrichlorosilane (C18) to form SAMs on silicon, to study the molecularpackingandtribologicalbehaviorofeachtypeof”lmasafunctionoftemperature.Fouriertransforminfraredspectroscopy(FTIR),contact angle,andatomicforcemicroscopy(AFM)wereusedtocharacterize”lms molecularpacking,surfaceenergy,androughness/friction,respectively.FTIR results show the peak position changes in discrete steps for C12 and C18 indicatingstructuraltransitionsthatresultinachangeinthemolecularpackingof the”lms.Ontheotherhand,theC6”lmpeakpositionwasconstantto500K, indicatingthatnochangeinthemolecularpackingstateoccurredoverthis temperaturerange.Frictionstudieshaveshownthatthemolecularpacking and tribological behavior of SAM ”lms at elevated temperatures is an importantconsiderationforMEMSandNEMSdevices,inordertooptimizeperformance and increase lifetimes.
