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1、ProceduresforImagingofStandardsatAtomic-ScaleResolutionUsingtheDigitalInstrumentsMultimodeAFMOrtizNanomechanicsLaboratory@MITF01I.SampleProducersandPreparation·MuscoviteMicaisayellowish,light-colored,transparenttotranslucentsilicate(subclass:phyllosilicat
2、es)mineralwiththefollowingchemistry:K2Al4Si6Al2O20(OH,F)4,Potassiumaluminumsilicatehydroxidefluoride.Itisahard,layered,crystalline(monoclinic2/m)materialthatfracturesalongweakatomicplanes("cleavage"planes),thuseasilyproducingatomicallyflatsurfacesofatomsh
3、avingaregularlatticestructurewhichareexcellentforuseinhigh-resolutionAFMpiezocalibrationandassubstratesforimagingofbiologicalsamples.Muscovitehasalayeredstructureofaluminumsilicatesheetsweaklybondedtogetherbylayersofpotassiumions.Thepotassiumionsoccupylar
4、geholesbetween12oxygenatoms,6fromthelayeraboveand6fromthelayerbelow;theresultingK-Oionicbondsare13ratherweakandeasilybroken.Thecleavagesheetsfairlyflexibleandelastic,hydrophilic,andnegativelychargedinwater.MuscoviteMicahaslowironcontentisagoodelectricalan
5、dthermalinsulator.MoredetailedinformationonMuscoviteMicacanbefoundhere:http://www.2spi.com/catalog/submat/mic_shet.html(*http://www.ill.fr/dif/3D-crystals/layers.html)AnothertypicalAFMsubstrateisHighlyOrderedPyrolyticGraphite(HOPG)whichisdescribedindetail
6、here:http://www.2spi.com/new/hopgsub.html·Afewsuppliersincludethefollowingcompanies:1)BioforceLab(http://www.bioforce.com)2)Structure-ProbeInc.(*http://www.2spi.com/catalog/afmstm.html),3)MicroscopyMart/PelcoInternational(*http://www.pelcoint.com/AFM.htm)
7、·Cleavagedirectionsaredetailedhere:http://www.2spi.com/catalog/submat/mica-disk.html·Attachtometalpuckandthentopiezoscannercap.II.RealTimeParameterSettings·contactmode,airorfluidcantileverholder(itistypicallymucheasiertoobtainimagesinwaterorbufferthaninai
8、r)·usestiffestspringconstantcantilever;onDIV-shapedcantileverchipsthisistheshortestonewithfattestlegs·useoxide-sharpenedSi3N4probetips,e.g.ModelNPSwhichhasthefollowingspecifications(http://www.di).com/products2/NewP
