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1、ExplorationofthegasphasechemistryinmicrowaveactivatedplasmasusedfordiamondchemicalvapourdepositionbyJieMaUniversityofBristolAthesissubmittedtotheUniversityofBristolinaccordancewiththerequirementsofthedegreeofDoctorofPhilosophyintheDepartmentofChemistry,Facul
2、tyofScience.April2008Wordcount:49,407AbstractAbstractTheworkpresentedinthisthesisfocusesonusinglaserspectroscopyandopticalemissionspectroscopy(OES)todiagnosemicrowaveactivatedhydrocarbon/Ar/H2andhydrocarbon/Ar/H2/B2H6plasmasusedindiamondchemicalvapourdeposit
3、ion.Twolaserspectroscopymethods,cavityring-downspectroscopy(CRDS)andtuneableinfraredlaserabsorptionspectroscopy(TIRLAS),havebeenemployed.IntheTIRLASexperiment,anovelquantumcascadelaser(QCL)wasusedtomeasuretheIRabsorptionsoftwostablehydrocarbonspecies,CH4andC
4、2H2,indifferenthydrocarbon/Ar/H2plasmas.ThefastfrequencychirpoftheQCLalsoallowstimeresolvedabsorptionmeasurements.AspectsofthegasphasechemistryofCH4andC2H2,andtheirinterconversion,wasthusexplored.CRDSisahighlysensitiveandaccurate,multi-passabsorptiontechniqu
5、e.Inthisthesis,ithasbeenappliedsuccessfullytomeasureabsolutecolumndensitiesof32C2(aΠu)andCH(XΠ)radicals,andH(n=2)atoms,andtheirspatialprofilesinCH4/Ar/H2plasma,asfunctionsofvariousdischargeparameters(power,pressure,CH4flowrate,Arflowrate).Thegastemperaturein
6、theplasmaregionwasalsodeterminedbymeasuringtheC2rotationaltemperature,andfoundtohavetypicalvaluesaround3000K.OEShasbeenusedtostudythebehaviourofseveralspecies(Ar,H,CH,C2,etc)emissionsinCH4/Ar/H2plasma,asfunctionsofdifferentdischargeparameters.Actinometrywasu
7、sedtoinvestigatethebehaviourofH(n=1)atomsintheplasma.ThespatialprofilesoftheseemissionswerealsomeasuredandcomparedwiththecolumndensityprofilesmeasuredinCRDSexperiments.Finally,B/C/HchemistrywasexploredinB2H6/Ar/H2/CH4plasma–usingCRDStomeasurecolumndensitieso
8、fBHradicals,andOEStomeasureemissionsfromBHandfromBatoms–underdifferentdischargeconditions.ThespatialprofilesofBHcolumndensitiesandemissionswerealsomeasuredandcompared.-i-Abstract-ii-Acknowledgem
