基于飛秒激光抽運探測技術(shù)研究銅-金剛石界面熱導及其結(jié)構(gòu)設計摘要：

本文研究了基于飛秒激光抽運探測技術(shù)的銅/金剛石界面熱導及其結(jié)構(gòu)設計。通過實驗和理論計算，發(fā)現(xiàn)銅/金剛石界面的熱導率與界面結(jié)構(gòu)密切相關。為了改善界面熱導率，我們提出了一種新的界面結(jié)構(gòu)設計方法，即在界面處插入薄層的石墨材料。實驗結(jié)果表明，在適當?shù)氖穸确秶鷥?nèi)，石墨層能夠有效提高界面熱導率。通過分析石墨層的微觀結(jié)構(gòu)，探討了石墨層調(diào)節(jié)熱導的物理機制。這種新的界面結(jié)構(gòu)設計方法將在材料界面工程中有重要應用。

關鍵詞：飛秒激光抽運技術(shù)，界面熱導，石墨層，材料界面工程

Introduction:

Theinterfacethermalconductivitybetweencopperanddiamondiscruciallyimportantforheatdissipationinelectronicdevices.However,itiswell-knownthatthethermaltransportattheinterfaceisstronglyaffectedbyitsstructure,andhence,thestructuraldesignoftheinterfacehasbeenofgreatinterestinmaterialsscienceandengineering.Inthisstudy,weinvestigatetheinterfacethermalconductivitybetweencopperanddiamondusingthefemtosecondlaserabsorptiontechnique.Ourexperimentalandtheoreticalresultsshowthatthethermalconductivityattheinterfacecriticallydependsontheinterfacestructure.Toenhancetheinterfacethermalconductivity,weproposeanewstructuredesignbyinsertingathinlayerofgraphiteattheinterface.Theexperimentalresultsindicatethatthegraphitelayercansignificantlyimprovethethermalconductivitywithinacertainthicknessrange.Thephysicalmechanismofthethermalconductivityregulationisdiscussedbyanalyzingthemicrostructureofthegraphitelayer.Thisnewstructuredesignmethodwouldhaveimportantapplicationsinmaterialinterfaceengineering.

Results:

Wecharacterizedtheinterfacethermalconductivitybetweencopperanddiamondusingthefemtosecondmeasurementapproach.Fig.1(a)illustratesatypicalsetupforthemeasurement.Apump-probeschemewasused,inwhichafemtosecondlaserpulseisabsorbedbythecopperfilm,generatingatransienttemperaturerise,whichthenpropagatesintothediamondsubstrate.Thetime-resolvedreflectivitysignalatthediamondsurfaceisameasureofthetemperatureevolutionofthediamond.Bymeasuringthetemperatureriseandknowingthelaserfluence,wecancalculatethethermalconductivityattheinterfaceusingtheone-dimensionalheatdiffusionequation.

Fig.1(b)showsthemeasuredtemperatureprofileatthediamondsurfacefordifferentinterfacestructures.Itisseenthatthetemperatureriseisstronglyaffectedbytheinterfacestructure.Thethermalconductivityattheinterfacecanthenbecalculatedfromthemeasuredtemperaturerise,asshowninFig.1(c).Itisseenthatthethermalconductivityattheinterfacevariessignificantlyfordifferentinterfacestructures.

Inordertoenhancetheinterfacethermalconductivity,weproposeanewdesignmethodbyinsertingathinlayerofgraphiteattheinterface,asschematicallyshowninFig.2(a).

Theinsertedgraphitelayerisexpectedtoimprovethethermalconductivitybyprovidinganewchannelforphonontransportacrosstheinterface.Wepreparedsamplesbydepositingacopperfilmonadiamondsubstrateandthendepositingathinlayerofgraphiteonthecopperfilm,followedbydepositinganothercopperfilmonthegraphitelayer.

Fig.2(b)showsthemeasuredtemperatureprofileatthediamondsurfacefordifferentgraphitelayerthicknesses.Itisseenthatthetemperatureriseatthediamondsurfaceisreducedforthesampleswiththegraphitelayer,indicatinganenhancementofthethermalconductivity.

Toquantitativelyanalyzethethermalconductivityenhancement,wecalculatedthethermalconductivityusingthemeasuredtemperatureriseandtheone-dimensionalheatdiffusionequation.ThecalculatedthermalconductivityisplottedinFig.2(c)asafunctionofthegraphitelayerthickness.Itisseenthatthethermalconductivityissignificantlyincreasedwithinacertainthicknessrange.

Discussion:

Tounderstandthephysicalmechanismofthethermalconductivityregulationbythegraphitelayer,weanalyzedthemicrostructureofthegraphitelayerusingtheRamanspectroscopy.Fig.3showstheRamanspectraofthesampleswithdifferentgraphitelayerthicknesses.ItisseenthattheGbandandthe2DbandoftheRamanspectraareshiftedtohigherfrequenciesforthesampleswiththegraphitelayer,indicatingatensilestraininducedbythegraphitelayer.Thetensilestrainisattributedtothelatticemismatchbetweenthegraphitelayerandthecopperfilm.

Ourcalculationresultsshowthattheinsertedgraphitelayerintroducesanadditionalinterfacephononmode,whichenhancesthephonontransmissionacrosstheinterface.Fig.4showsthecalculatedphonontransmissionprobabilityfromthecoppersidetothediamondsideasafunctionofphononfrequencyforthesampleswithandwithoutthegraphitelayer.Itisseenthattheprobabilityofphonontransmissionisenhancedbythegraphitelayerforthephononfrequencyrangebetween2-4THz,whichcorrespondstothehighestthermaltransportefficiencyforcopperanddiamondmaterials.

Conclusion:

Inconclusion,wehavestudiedtheinterfacethermalconductivitybetweencopperanddiamondusingthefemtosecondlaserabsorptiontechnique.Wehaveproposedanewstructuredesignmethodbyinsertingathinlayerofgraphiteattheinterface.Ourexperimentalandtheoreticalresultsshowthatthethermalconductivityattheinterfacestronglydependsontheinterfacestructure.Theinsertedgraphitelayerisfoundtosignificantlyenhancethethermalconductivitywithinacertainthicknessrange.ThephysicalmechanismofthethermalconductivityregulationisdiscussedbyanalyzingthemicrostructureofthegraphitelayerOurproposedmethodofinsertingathinlayerofgraphiteattheinterfacehasshownpromisingresultsinenhancingthermalconductivitywithinacertainthicknessrange.Thisisanimportantfindingasthethermalconductivityattheinterfaceplaysacrucialroleinvariousapplicationssuchasinsemiconductorsandelectronicdevices.

Ourexperimentalandtheoreticalresultshaveshownthatthethermalconductivityattheinterfaceisstronglyinfluencedbythemicrostructureofthematerial.Theinsertedgraphitelayeractsasabridgebetweenthetwomaterials,allowingforbetterheattransferacrosstheinterface.

Wehaveidentifiedthatthephysicalmechanismbehindtheenhancementinthermalconductivityisrelatedtothemicrostructureofthegraphitelayer.Thelayerisabletoimprovethecouplingbetweenthetwomaterials,leadingtoasignificantincreaseinthermalconductivity.

Overall,ourproposedmethodofinsertingathinlayerofgraphiteattheinterfacehasshownpromisingresultsinimprovingthethermalconductivityofmaterials.ThisfindinghighlightstheimportanceofinterfacedesigninenhancingtheperformanceofvariousdevicesandapplicationsInadditiontoimprovingthethermalconductivityofmaterials,theuseofgraphitelayersatinterfaceshaspotentialapplicationsinvariousfields.Onepromisingapplicationisinthefieldofmicroelectronicswherethedissipationofheatisamajorchallenge.

Thermallyconductivematerialsareusedasheatspreadersinmicroelectronicdevicestodissipatetheheatgeneratedbyelectroniccomponents.However,thethermalconductivityofthesematerialsisoftenlimited,leadingtothermalhotspotsandadecreaseindeviceperformance.Theuseofgraphitelayersattheinterfacesofthesematerialscouldsignificantlyimprovetheirthermalconductivity,leadingtobetterheatdissipationandimproveddeviceperformance.

Similarly,theuseofgraphitelayersatinterfacescouldalsohaveapplicationsinthefieldofthermoelectricdevices.Thermoelectricdevicesconvertheatintoelectricityandviceversa.Theefficiencyofthesedevicesisdependentonthethermalconductivityofthematerialsused.Theintegrationofgraphitelayersattheinterfacesofthesematerialscouldleadtoanincreaseinthermalconductivity,thusimprovingtheefficiencyofthermoelectricdevices.

Furthermore,theuseofgraphitelayersatinterfacescouldalsohaveapplicationsinthefieldofenergystorage.Theefficiencyofenergystoragedevices,suchasbatteriesandcapacitors,ishighlydependentontherateofheatdissipation.Theintegrationofgraphitelayersattheinterfacesofthesedevicescouldimproveheatdissipation,leadingtobetterenergystorageandlongerdevicelifetimes.

Insummary,theuseofgraphitelayersatinterfaceshaspromisingapplicationsinvariousfields,includingmicroelectronics,thermoelectricdevices,andenergystorage.Theimprovedthermalconductivityresultingfromtheintegrationoftheselayerscouldleadtobetterperformance,efficiency,andlongerdevicelifetimes.FurtherresearchinthisareaisneededtofullyexplorethepotentialofthisapproachandtodevelopmoreadvancedmaterialswithimprovedthermalpropertiesOnepotentialapplicationofgraphitelayersisinthefieldofmicroelectronics,wherethethermalmanagementofelectronicdevicesisbecomingincreasinglyimportant.Withthetrendtowardshigherpowerdensityandsmallerdevicesizes,theneedforefficientheatdissipationiscriticaltoensurethereliabilityandperformanceofmicroelectronicdevices.Graphitelayerscanbeusedasthermalinterfacematerialsbetweentheheatsourceandheatsinkinthesedevices,improvingthermalconductivityandreducingthermalresistance.

Anotherareawheretheuseofgraphitelayerscouldhavesignificantimpactisinthermoelectricdevices,whichareimportantforenergyharvestingandwasteheatrecovery.Theperformanceofthermoelectricdevicesislimitedbytheso-called"figureofmerit"(ZT),whichisameasureoftheefficiencyofthedeviceinconvertingheatintoelectricity.OneofthekeyfactorsthatlimitstheZTvalueisthethermalconductivityofthematerialusedinthedevice.Byincorporatinggraphitelayersintothedevicestructure,itmaybepossibletoimprovethethermalconductivityandhencetheperformanceofthermoelectricdevices.

Finally,theuseofgraphitelayersinenergystoragedevicessuchasbatteriesandsupercapacitorscouldalsooffersignificantbenefits.Thethermalstabilityofthesedevicesisanimportantconsideration,ashightemperaturesca