Modeling of the gas-phase chemistry in C-H-O gas mixtures for diamond Chemical Vapor Deposition

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1、JOURNALOFAPPLIEDPHYSICSVOLUME89,NUMBER91MAY2001Modelingofthegas-phasechemistryinC–H–Ogasmixturesfordiamondchemicalvapordepositiona)JamesR.Petherbridge,PaulW.May,andMichaelN.R.AshfoldSchoolofChemistry,UniversityofBristol,Bristol,BS81TSUnitedKingdom~Received21November2000

2、;acceptedforpublication8February2001!TheboundariesofthediamonddepositionregionintheC±H±O~Bachmann!atomicphasecompositiondiagramhavebeenreproducedsuccessfullyfor38differentC,H,andOcontaininggasmixturesusingtheCHEMKINcomputerpackage,togetherwithjusttwocriteriaÐaminimummol

3、efractionofmethylradicals@CH3#andalimitingvalueofthe@H#/@C2H2#ratio.Thediamondgrowth/no-growthboundarycoincideswiththelinealongwhichtheinputmolefractionsofCandOareequal.Foreverygasmixturestudied,no-growthregionsarefoundtocoincidewithanegligible(,10210)molefractionofCHra

4、dicals,whileforgasmixtureslyingwithinthediamond3growthregiontheCHmolefractionis;1027.Eachno-growth!diamondgrowthboundaryis3seentobeaccompaniedbya2±3orderofmagnitudestepinCH3molefraction.Theboundarybetweendiamondandnondiamondgrowthislessclearlyde®ned,butcanbereproducedby

5、assumingacritical,temperaturedependent@H#/@C2H2#ratio~0.2,inthecasethatTgas52000K!thatre¯ectsthecrucialroleofHatomsintheetchingofnondiamondphases.Theanalysisallowspredictionofthecompositionprocesswindowforgoodqualitydiamondgrowthforallstableinputgasmixturesconsideredint

6、hisstudy.©2001AmericanInstituteofPhysics.@DOI:10.1063/1.1360221#I.INTRODUCTIONmodelthatconsideredbothgasphaseandgas-surfacechem-istrytocalculatemolefractionsofC,H,andOcontainingLow-pressurediamonddepositionhasbeenachievedus-radicalspecies,whichwerethenplottedintheformof

7、aingalargerangeofC,H,andOcontaininggasmixtures.ternaryC±H±Odiagram.Wenote,however,thatthisstudy1,2Bachmannetal.summarizedtheresultsofmanydeposi-coversonlyasmallsectionoftheconventionalBachmanntionexperimentsinvolvingvariousgasmixturesandreactordiagram.HerewepresentCHEMK

8、INsimulationsofgasmix-typesintheformofanatomicC±H±Ophasediagram.Theyturescorrespondingto38cutsthroughlargewide