[1~5] sp 2 C sp 3 C [17] (ta-c) sp 2 C sp 3 C 250~1700nm 380~1700nm XPS ta-c ta-c sp 2 -πc sp 3 -σc sp 2 C 2 sp 3 C 2.1 FCVA ta-c sp 2 C sp 3 C ta-c (

32 10 Vol.32No.10 2012 10 ACTAOPTICASINICA October2012 ( 315201) (FCVA) (ta-c) (SE) ta- C sp 3 C sp 2 C X (XPS) -100V 33.9nm; sp 2 C sp 3 C ta-c sp 2 C sp 3 C sp 2 C 250~1700nm ; ; ; O484.41 A doi:10.3788/aos201232.1031005 DeterminationofChemicalBondofTetrahedralAmorphous CarbonFilmsbyElipsometryApproach LiXiaowei ZhouYi SunLili WangAiying (Ningbo Key Laboratoryof MarineProtection MaterialsNingboInstituteof MaterialTechnologyand Engineering ChineseAcademyofSciencesNingboZhejiang315201China) Abstract Tetrahedralamorphouscarbon(ta-C)filmsunderdiferentsubstratenegativebiasarepreparedbyahome developedfilteredcathodicvacuumarc(fcva)technologywithdoublebendshape.thefilmthicknessismeasured byacombinedspectrophotometryandspectroscopicelipsometry (SE)approach;thechemicalbondsincludingsp 2 C andsp 3 Caregainedbythefitedelipsometrymethod.Furthermoretheaccuracyofelipsometryresultsisevaluated bycomparingwiththoseofx-rayphotoelectronspectroscopy(xps)andramanspectra.theresultsindicatethatthe minimumthicknessofta-cfilmof33.9nmisobtainedwhenthebiasvoltageis -100V;withtheincreaseofbias voltagethe optical gaps and the content ofsp 3 C atomic bond decrease while the sp 2 C contentincreases correspondingly.bycomparison withtheresultsofxpsand Ramanspectraitisfoundthat whentheoptical constantsofsp 2 C modelarerepresentedbytheglassycarbonandthefitingwavelengthrangesarechosenfrom250 to1700nmthebestfitingresultofatomicbondsofta-cfilmscanbededucedbytheelipsometry method. Thereforeitcouldbesaidthattheeliposometrymethodisaquitepromisingmethodtocharacterizetheatomicbonds ofta-cfilmsincludingsp 2 Candsp 3 Casanewnondestructivefastquantitativeandeasyway. Keywords thinfilms;chemicalbond;elipsometryapproach;filteredcathodicvacuumarc;tetrahedralamorphous carbon OCIScodes 240.2130;310.4925;310.6860 1 :2012-04-01; :2012-05-28 : (Y4100312) (2011B1016) (2010D10015 2010A0203) : (1982 ) E-mail:lixw@nimte.ac.cn : (1975 ) E-mail:aywang@nimte.ac.cn( ) 1031005-1

[1~5] sp 2 C sp 3 C [17] (ta-c) sp 2 C sp 3 C 250~1700nm 380~1700nm XPS ta-c ta-c sp 2 -πc sp 3 -σc sp 2 C 2 sp 3 C 2.1 FCVA ta-c sp 2 C sp 3 C ta-c ( 99.99%) ta-c 1mm (525±5) μ m sp 2 C sp 3 C p (100) : sp 3 /sp 2 [6] X (XPS) [7] (EELS) [8] 10~15 min (NMR) [9] ; 2.67 10-3 Pa sp 2 C Ar(0 1 sp 3 C π 20mL/min) -400V 4 min; σ sp 2 C 0-50 -100-150V sp 3 C 50~100 Ar 1 ml/min sp 3 C 4.66 10-3 Pa 10min 60A EELS sp 2 C sp 3 C 20V 6 4 4 4A ta-c 2.2 NMR XPS ta-c C1s [16] sp 2 C sp 3 C PerkinElmer Lambda950 - (VIS-NIR) ta-c / / sp 2 C sp 3 C ta-c 250~1700nm (SE) 1nm [1011] sp 3 C sp 2 C J.A.Woolam M- 2000DI (VariableAngle [12~15] SpectroscopicElipsometry) Ψ Δ sp 2 C sp 3 C sp 2 C 0.015 250~1700nm [16] (FCVA) 55 60 65 ta-c WVASE32 1031005-2

: 2.3 ta-c ta-c fsp2+ fsp3+fvoid=1; sp 2 C fsp2 sp 3 C fsp3 fvoid; 250~1700nm 380~1700nm; (EMA) Bruggeman ta-c sp 3 /sp 2 AXIS 1 ta-c UTLTRADLD[Al(mono)Kα (160eV)Ar + Fig.1 Thicknessofta-Cfilmsatdiferent 5min] X JY biasvoltages LabRam HR800 ta-c k XPS : ta-c 532.2nm 50 120s sp 3 C sp 2 C 3 sp 3 /sp 2 ta-c 3.1 1 ta-c sp 2 C sp 2 [18] ; -100 V sp 2 C ta-c 33.9nm 3.4nm/min ta-c p 3.2 ta-c Tauc α 2 55 ta-c E opt WVASE32 αhv =A(hv-E opt ) 2 (1) (αhv) 1/2 =A(hv-E opt ) (2) ta-c hv A 3 ta-c (αhv) 1/2 hv n 2.37~2.72 ; ta-c E opt 4 2 55 ta-c (a)ψ;(b)δ Fig.2 Elipsometryspectraofta-Cfilmswiththeincidentangleof55 atdiferentbiasvoltages.(a)ψ;(b)δ 1031005-3

3 ta-c n k (a)n;(b)k Fig.3 Refractionindexnandextinctioncoeficientkofta-Cfilmsatdiferentbiasvoltages.(a)n;(b)k ta-c sp 3 C sp 2 C sp 2 C 250~1700nm 380~1700nm 1 1 (MSE) 10 ;sp 3 C ta-c sp 2 C 250~ 1700nm sp 2 C 0-150V ta-c sp 3 C 62.6% 28.6% 4 ta-c sp 2 C Fig.4 Opticalbandgapofta-Cfilmsatdiferent sp 3 /sp 2 sp 3 C biasvoltages sp 2 C 0-150 V ta-c sp 2 C 1.42eV 0.88eV sp 3 C sp 2 C 0-150V sp 3 C 3.3 sp 3 /sp 2 26% 44.1% ta-c sp 2 C sp 2 C 1 sp 3 C sp 2 C Table1 Contentsofsp 3 Candsp 2 Cinta-Cfilmsbyelipsometryapproach Wavelength/nm 250~1700 Wavelength/nm 380~1700 Substratebias/V Glasscarbonforsp 2 C Graphiteforsp 2 C sp 3 /sp 2 sp 3 /% MSE sp 3 /sp 2 sp 3 /% MSE 0 1.68 62.6 2.37 7.78 88.6 2.37-50 1.34 57.3 1.096 6.57 86.8 1.096-100 0.71 41.5 1.305 4 80 1.305-150 0.4 28.6 1.209 2.66 72.7 1.214 Substratebias/V Glasscarbonforsp 2 C Graphiteforsp 2 C sp 3 /sp 2 sp 3 /% MSE sp 3 /sp 2 sp 3 /% MSE 0 6.29 86.3 0.4603 15.09 93.8 0.4603-50 4.33 81.2 3.599 10.2 91.1 4.416-100 1.98 66.4 2.113 5.6 84.4 1.991-150 1.14 53.3 2 3.16 76 1.948 1031005-4

: sp 2 C C-O ( ) 380~1700nm sp 3 C 3.4 XPS sp 3 C sp 2 C ta-c sp 3 /sp 2 sp 3 sp 2 XPS XPS- sp 3 C 2 PEAK41 ta-c XPS-C1s Shirley ; sp 3 C 64.6% 31.2% sp 2 C sp 3 C 0.8eV [19] 5 sp 2 C sp 3 C sp 2 C sp 3 C sp 2 C sp 3 C ta-c 0-150Vta-C 5 ta-c XPS-C1s Fig.5 XPS-C1sspectraofta-Cfilmsatdiferentsubstratenegtivebiasvoltages 2 ta-c XPS Table2 XPSfitingresultsofta-Cfilmsatdiferentsubstratenegtivebiasvoltages Substratebias/V sp 2 Cpeakposition/eV sp 3 Cpeakposition/eV C-Opeakposition/eV sp 3 /sp 2 sp 3 /% 0 283.825 284.625 285.115 1.826 64.6-50 283.890 284.690 285.227 1.327 57.0-100 284.463 285.263 285.850 0.699 41.1-150 284.470 285.270 286.079 0.454 31.2 ta-c sp 3 /sp 2 π G [20] π [2122] ta-c 6 D sp 3 / 900~1000cm -1 sp 2 fityk 1200~1700cm -1 1590cm -1 sp 2 1332cm -1 D 1558cm -1 G I d /I g G 1031005-5

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