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1、JOURNALOFAPPLIEDPHYSICSVOLUME89,NUMBER215JANUARY2001LowtemperaturediamondgrowthusingCO2ÕCH4plasmas:Molecularbeammassspectrometryandcomputersimulationinvestigationsa)JamesR.Petherbridge,PaulW.May,SeanR.J.Pearce,KeithN.Rosser,andMichaelN.R.AshfoldSchoolofChe
2、mistry,UniversityofBristol,Bristol,BS81TSUnitedKingdom~Received21August2000;acceptedforpublication23October2000!Microwaveplasmaenhancedchemicalvapordepositionhasbeenusedtogrowdiamond®lmsatsubstratetemperaturesdownto435°CusingCO2/CH4gasmixtures.AnArrheniusp
3、lotofgrowthrateasafunctionofsubstratetemperatureyieldsavaluefortheactivationenergyforthegrowthstepof28kJmol21.ThisislowerthanthatmeasuredpreviouslyforCH/Hsystemsandhintsat42adifferentgas-surfacechemistrywhenusingCH4/CO2plasmas.Molecularbeammassspectrometry
4、hasbeenusedtomeasuresimultaneouslytheconcentrationsofthedominantgasphasespeciespresentduringgrowth,forawiderangeofplasmagasmixtures~0%±80%CH4,balanceCO2).TheCHEMKINcomputerpackagehasalsobeenusedtosimulatetheexperimentalresultsinordertogaininsightintothemaj
5、orreactionsoccurringwithinthemicrowaveplasma.Thecalculatedtrendsforallspeciesagreewellwiththeexperimentalobservations.Usingthesedata,themodelforthegasphasechemistrycanbereducedtoonlyfouroverallreactions.Our®ndingssuggestthatCH3radicalsarelikelytobethekeygr
6、owthspecieswhenusingCO2/CH4plasmasandprovideaqualitativeexplanationforthenarrowconcentrationwindowfordiamondgrowth.©2001AmericanInstituteofPhysics.@DOI:10.1063/1.1333031#I.INTRODUCTION50%CH/50%CObyvolume¯owrate.7,8Suchgasmixtures42areunusualinthattheyconta
7、innoinputhydrogen,comparedTheoutstandingpropertiesofdiamond®lmsgrownbytotheexcessusedinothergasmixtures~althoughthecon-chemicalvapordeposition~CVD!haveattractedmuchinter-centrationofHintheactivatedgasmixtureisapproxi-21,2estduringrecentyears.Thenowwell-est
8、ablishedcondi-matelyhalfthatseeninCH4/H2mixtures!.Ithasbeentionsfordiamondgrowthincludetheuseofsubstratetem-proposed9thatO,O,andOHspeciesintheplasmaperform2peratures.700°Candacarbon-containingprecursorgassome
