Designation:F1438−93(Reapproved2012)StandardTestMethodforDeterminationofSurfaceRoughnessbyScanningTunnelingMicroscopyforGasDistributionSystemComponents1ThisstandardisissuedunderthefixeddesignationF1438;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONSemiconductorcleanroomsareservicedbyhigh-puritygasdistributionsystems.Thistestmethodpresentsaprocedurethatmaybeappliedfortheevaluationofoneormorecomponentsconsideredforuseinsuchsystems.1.Scope1.1Thepurposeofthistestmethodistodefineamethodforanalyzingthesurfacetextureoftheabove-mentionedcompo-nentsusingascanningtunnelingmicroscope(STM).STMisanoncontactmethodofsurfaceprofilingthatcanmeasurethree-dimensionalsurfacefeaturesinthenanometersizerange,whichcanthenbeusedtorepresentthesurfacetextureortoprovidefiguresofmerit.Applicationofthistestmethod,wheresurfacetextureisusedasaselectioncriterion,isexpectedtoyieldcomparabledataamongdifferentcomponentstested.1.2Limitations:1.2.1ThistestmethodislimitedtocharacterizationofstainlesssteelsurfacesthataresmootherthanRa=0.25µm,asdeterminedbyacontact-stylusprofilometeranddefinedbyANSIB46.1.Themagnificationsandheightscalesusedinthistestmethodwerechosenwiththissmoothnessinmind.1.2.2Intentionaletchingorconductivecoatingofthesur-faceareconsideredmodificationsofthegas-wettedsurfaceandarenotcoveredbythistestmethod.1.2.3Thistestmethoddoesnotcoversteelsthathaveanoxidelayertoothicktopermittunnelingunderthetestconditionsoutlinedin11.3.1.3ThistechniqueiswrittenwiththeassumptionthattheSTMoperatorunderstandstheuseoftheinstrument,itsgoverningprinciples,andanyartifactsthatcanarise.Discus-sionofthesepointsisbeyondthescopeofthistestmethod.1.4ThevaluesstatedinSIunitsaretoberegardedasthestandard.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itis...
