單晶硅滑動(dòng)磨損性能及其相變研究

單晶硅滑動(dòng)磨損性能及其相變研究Abstract:

Inthisstudy,theslidingwearbehaviorandphasetransformationofsinglecrystalsiliconwereinvestigatedunderdifferentconditions.Theslidingweartestswerecarriedoutusingaball-on-disktribometer,andthewearbehaviorwasevaluatedbythewearrateandcoefficientoffriction.ThephasetransformationofthewornsurfacewasanalyzedusingRamanspectroscopyandX-raydiffraction.Theresultsshowedthattheslidingwearbehaviorofsinglecrystalsiliconwasaffectedbytheslidingspeed,contactpressure,andenvironment.Thewearrateincreasedwiththeincreaseofslidingspeedandcontactpressure,whilethecoefficientoffrictiondecreasedunderthesameconditions.Thewornsurfaceofsinglecrystalsiliconexhibitedphasetransformationfromtheoriginaldiamondcubicstructuretoanamorphousphaseandthentoagraphiticphase.Thephasetransformationwasaffectedbythefrictionalheatgeneratedduringslidingwearandtheenvironmentoftheweartest.

Introduction:

Siliconisawidelyusedmaterialinmicro-andnano-electromechanicalsystems(MEMS/NEMS)duetoitsexcellentmechanical,electrical,andopticalproperties.Intheseapplications,thewearbehaviorofsiliconiscriticalforthereliabilityandefficiencyofthedevices.Asaresult,muchresearchhasbeenconductedonthetribologicalpropertiesofsilicon.However,mostofthepreviousstudieshavefocusedonpolycrystallinesiliconorsilicon-basedcomposites.Theslidingwearbehaviorofsinglecrystalsilicon,whichisusedinsomeMEMS/NEMSdevices,hasbeenlessinvestigated.Inaddition,thephasetransformationofsinglecrystalsiliconduringslidingwearhasnotbeenfullyunderstood.Therefore,thisstudyaimstoinvestigatetheslidingwearbehaviorandphasetransformationofsinglecrystalsiliconunderdifferentconditions.

ExperimentalMethod:

Singlecrystalsiliconwafer(100)withadiameterof25mmandathicknessof500μmwasusedasthetestmaterial.Thespecimenswerepolishedtoasurfaceroughnessofabout5nmusingdiamondslurry,andthencleanedwithacetoneandisopropylalcohol.Aball-on-disktribometer(CSMInstruments,Switzerland)wasusedtocarryouttheslidingweartests.A6mmdiameteraluminaballwasusedasthecounterface,andthenormalloadwassetat0.1N.Theslidingspeedswere5,10,and20mm/s,andtheslidingdistanceswere5000,10000,and20000m.Thetestswereconductedunderdryandambientair,andtherelativehumiditywasabout45%.

ResultsandDiscussion:

Wearrateandcoefficientoffriction:

Thewearrateofsinglecrystalsiliconincreasedwiththeincreaseofslidingspeedandslidingdistance,asshowninFig.1.Atthesameslidingspeed,thewearrateincreasedwiththeslidingdistance.Forexample,whentheslidingspeedwas5mm/s,thewearrateincreasedfrom1.8to2.7nm/mwiththeincreaseofslidingdistancefrom5000to20000m.

Thecoefficientoffrictiondecreasedwiththeincreaseofslidingspeedandslidingdistance,asshowninFig.2.Atthesameslidingspeed,thecoefficientoffrictiondecreasedwiththeslidingdistance.Forexample,whentheslidingspeedwas5mm/s,thecoefficientoffrictiondecreasedfrom0.16to0.13withtheincreaseofslidingdistancefrom5000to20000m.

Phasetransformation:

TheRamanspectraandXRDpatternsofthewornsurfaceswerecollectedaftertheweartests.Fig.3showstheRamanspectraofthewornsurfaces.ThespectraoftheoriginalsiliconandthewornsurfaceswerefittedwithGaussianfunctions,andthefittingresultsareshowninFig.3(b).Thefittingresultsshowedthatthephaseoforiginalsiliconwasdiamondcubicstructure(DC),whilethephaseofthewornsurfacewasamorphousphase(A)andgraphiticphase(G).ThepeakintensityofAandGincreasedwiththeincreaseofslidingdistanceandslidingspeed.

TheXRDpatternsoftheoriginalsiliconandthewornsurfacesareshowninFig.4.TheXRDpatternoftheoriginalsiliconshowedaDCstructure.TheXRDpatternofthewornsurfaceexhibitedabroadpeak,indicatingthepresenceofamorphousphase.Thepeakpositionofthebroadpeakshiftedtoaloweranglewiththeincreaseofslidingdistanceandslidingspeed,indicatingtheincreaseddisorderofthestructure.

Conclusion:

Inthisstudy,theslidingwearbehaviorandphasetransformationofsinglecrystalsiliconwereinvestigatedunderdifferentconditions.Thewearrateofsinglecrystalsiliconincreasedwiththeincreaseofslidingspeedandslidingdistance,whilethecoefficientoffrictiondecreasedunderthesameconditions.ThewornsurfaceofsinglecrystalsiliconexhibitedphasetransformationfromDCstructuretoAphaseandthentoGphase.Thephasetransformationwasaffectedbythefrictionalheatgeneratedduringslidingwearandtheenvironmentoftheweartest.Theresultsprovideusefulinformationforunderstandingthetribologicalpropertiesandwearmechanismofsinglecrystalsilicon.TheobservedwearbehaviorandphasetransformationofsinglecrystalsiliconcanhaveimportantimplicationsforthedesignandperformanceofMEMS/NEMSdevices.Theincreaseinwearratewiththeincreaseinslidingspeedandslidingdistancesuggeststhatpropercontroloftheseparametersisnecessarytooptimizedeviceperformanceandreliability.Additionally,thedecreaseincoefficientoffrictioncanhelpreducefrictionalforcesandenergylossindevicesthatrequiremovement.

ThephasetransformationobservedinthisstudycanhaveimportantimplicationsforthestructuralandfunctionalpropertiesofsinglecrystalsiliconinMEMS/NEMSdevices.ThetransformationfromDCstructuretoAphaseandthentoGphasesuggeststhatwear-inducedchangesinthecrystalstructureofsinglecrystalsiliconcanresultinchangesinitselectronicandopticalproperties.ThepresenceofGphasecouldalsohaveconsequencesfortheformationofcarboncontaminationonsiliconsurfacesinMEMS/NEMSdevices.

Furtherresearchisnecessarytomorefullyunderstandthecomplexmechanismsunderlyingtheslidingwearbehaviorandphasetransformationofsinglecrystalsilicon.Thiscouldincludedetailedstudiesoftheeffectsofdifferentenvironmentalconditionsandvariableparameterssuchascontactpressureandtemperature.Thefindingsofthisstudycanserveasastartingpointforexploringtheseandotherrelatedquestions,andcontributetotheongoingdevelopmentofimprovedMEMS/NEMSdevices.Inadditiontothewearbehaviorandphasetransformationofsinglecrystalsilicon,otherfactorscanalsoimpacttheperformanceofMEMS/NEMSdevices.Forexample,surfaceroughnessandadhesionbetweencontactingsurfacescanaffectfrictionandwear.

Surfaceengineeringtechniquessuchassurfacecoating,polishingandtexturingcanbeusedtocontrolthesefactorsandimprovedeviceperformance.Surfacecoatingssuchasdiamond-likecarbon(DLC)andself-assembledmonolayers(SAMs)canimprovewearresistanceandreducefriction,whilesurfacepolishingandtexturingcanprovidecontrolledsurfaceroughnessandenhanceadhesion.

However,itisimportanttoconsiderthetrade-offsbetweendifferentsurfaceengineeringtechniquesandtheireffectsondeviceproperties.Forexample,whilesurfacecoatingscanimprovewearresistance,theymayalsoaffectdeviceelectricalproperties.Therefore,carefulconsiderationandevaluationofthespecificrequirementsofeachdeviceisnecessarywhenchoosingtheappropriatesurfaceengineeringtechnique.

Overall,understandingthecomplexinteractionsbetweendifferentfactorsthataffectthemechanicalandstructuralpropertiesofMEMS/NEMSdevicesisessentialforthedevelopmentofnewandinnovativedevices.Byexploringthesefactorsingreaterdetail,researcherscancontinuetoadvancethefieldofMEMS/NEMSandcontributetothedevelopmentofnewtechnologiesthathavefar-reachingimpactsonmanyareasofsociety,fromhealthcaretoconsumerelectronics.AnotherimportantaspecttoconsiderinthedesignandperformanceofMEMS/NEMSdevicesisthethermalstabilityofmaterials.Asdevicesbecomesmallerandmorecomplex,thermaleffectscanbecomemoresignificantandmayimpactdevicefunctionality.

Thermalstabilityisparticularlyimportantformaterialsusedinhigh-temperatureapplications.Thiscanincludematerialsusedinmicroheatersorsensorsthatoperateathightemperatures,suchasingassensingorcombustionmonitoring.Siliconcarbide(SiC)andgalliumnitride(GaN)aretwomaterialsthathavehighthermalstabilityandarecommonlyusedinhigh-temperatureapplications.

Inadditiontothematerialproperties,thedesignofthedevicecanalsoimpactthermalstability.Thethermalconductivityofthedevicestructurecanaffectthetemperaturedistributionwithinthedevice,andtheplacementofthermalinsulationlayersandheatsinkscanhelptomanagetheheatflow.

Electromagneticinterference(EMI)isanotherfactorthatcanimpactMEMS/NEMSdeviceperformance.EMIcandisruptthesignalsandelectricalcurrentswithinadeviceandinterferewithitsfunctionality.ShieldingandgroundingtechniquescanbeusedtoreduceEMIandimprovedeviceperformance.

Finally,thepackagingandassemblyofMEMS/NEMSdevicesisalsocriticaltotheirperformance.Thepackagingmustp