SEM Sample Preparation
description
Transcript of SEM Sample Preparation
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SamplepreparationforScanningelectronmicroscopy(SEM)SEMisprimarilyusefulforgivingathreedimensionalimageofthesurfaceofthespecimenandisforviewinglargeobjects.AswithTEM,specimensareimagedwithabeamofelectrons,butinsteadoftheelectronsbeingtransmittedthroughthespecimen,thebeamis"scanned"across,creatinganimageofthesurfaceofthesample,withexceptionaldepthoffield.Thisimageisachievedviathedetectionof"secondary"electronsthatarereleasedfromthespecimenasaresultofitbeingscannedbyveryhighenergy"primary"electrons(ie.thoseemittedfromtheelectron"gun"intheSEM).Asmostbiologicalspecimensaremadeupofnondensematerialtheamountofsecondaryelectronsproducedistoolowtobeofmuchuseincreatinganimageandthereforetheyareusuallycoatedwithaveryfinelayerofametalwhichreadilyproducessecondaryelectrons.Thelargedepthoffieldachievablecanproduceanimageofgreatvisualdepthwithathreedimensionalappearance.Theoperatingenvironmentofastandardscanningelectronmicroscopedictatesthatspecialistpreparationtechniquesareused.Typically,abiologicalspecimenischemicallyfixed,dehydratedthroughanacetoneorethanolseriesandthendriedatthecriticalpointamethodusedtominimizespecimendistortionduetodryingtensions.Fordrysamples,thisprocessisnotnecessary.SEMcanalsobeusedtoinvestigatesmoothsurfacesofindustrialsamples.Thesamplesaremountedonastubofmetalwithadhesive,coatedwith4060nmofmetalsuchasGold/Palladiumandthenobservedinthemicroscope.Everysampleisdifferent.PleaseconsultwiththeEMStaffbeforestartingaproject.
Epidermoidcarcinomacells.Bar:2m
Epidermoidcarcinomacells.Bar:2m
StaphylococcusAureus.Bar:2m
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Smallintestine,villi.Bar:200m.
Smallintestine,microvillionthesurfaceofavillus.
Plastinatedglomerulusfromrat.Tissueisremoved.Bar:50m.
FlyBar:200m.
SpiderBar:300m.
Haironthesurface.Bar:10m.
SEMservicesinclude: Fixationanddehydration Criticalpointdrying Dryingwithhexamethyldisilazane(HMDS)andtButanol CoatingwithGold/PalladiumusingSputtercoater Imageprocessing(softwareScandium)