⎇ⓥ⺖㗴ฬ㧦⥄↱㔚ሶ࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦᴺߦࠃࠆⅣႺඨዉ૕ᚑ⤑⎇ⓥઍ⴫⠪㧦㋈ᧁ⮍(ᣣᧄᄢቇℂᎿቇㇱ㔚᳇Ꮏቇ⑼)⎇ⓥᓥ੐⠪㧦ዊᨋ዁ᄥ㇢(ᣣᧄᄢቇℂᎿቇ⎇ⓥ⑼㔚᳇Ꮏቇኾ᡹)↰ਛᘮᒾ(ᣣᧄᄢቇℂᎿቇ⎇ⓥ⑼㔚᳇Ꮏቇኾ᡹)⋉↰ᕺᄥ(ᣣᧄᄢቇℂᎿቇ⎇ⓥ⑼㔚᳇Ꮏቇኾ᡹)ᷡ᳓ᵗᐔ(ᣣᧄᄢቇℂᎿቇ⎇ⓥ⑼㔚᳇Ꮏቇኾ᡹)౒ห⎇ⓥ⠪㧦૒⮮᣽ᙗ( 㚤Ỉᄢቇක≮ஜᐽ⑼ቇㇱ᡼኿✢⑼)‫⎇ޣ‬ⓥ⋡⊛‫ޤ‬ⅣႺඨዉ૕ߣߪࠢ࡜࡯ࠢᢙ㧔࿾Ზਛߢߩర⚛ߩሽ࿷Ყ₸㧕ߩ㜞޿ర⚛߿ᬀ‛߿േ‛߇↢↥ߔࠆర⚛ߥߤࠍ↪޿ࠆߎߣߢ‫ޔ‬ⅣႺߦૐ⽶⩄ߢ࡝ࠨࠗࠢ࡞₸߇㜞ߊ‫ੱޔ‬૕ߦኻߒߡᲥᕈࠍᜬߚߥ޿․ᕈࠍ
᦭ߔࠆඨዉ૕ࠍ⋡ᜰߒߚ߽ߩߢ޽ࠆ‫ޕ‬࿾⃿ⅣႺߦఝߒߊ㧘⾗Ḯߩ⼾ንߥ᧚ᢱߢ૞⵾ߐࠇߚඨዉ૕ߩ
ⷐ᳞ߦኻᔕߢ߈ࠆⅣႺඨዉ૕ߣߒߡ‫ࠢ࡯࡜ࠢߪߦ⥸৻ޔ‬ᢙߩ㜞޿㋕(Fe)ߣࠪ࡝ࠦࡦ(Si)ࠍ↪޿ߡᾲ㔚ᄌ឵⚛ሶ߿ᄥ㓁㔚ᳰߣߒߡߩ೑↪߿࠺ࡃࠗࠬߦᔕ↪ߔࠆߎߣߢ⦟ᅢߥ․ᕈ߇ᓧࠄࠇࠆߣᦼᓙߐࠇ
ߡ޿ࠆ‫ޔߦઁߩߘޕ‬ᚒ‫ߪޘ‬ᬀ‛߿േ‛߇↢↥ߔࠆ᦭ᯏ‛⾰ࠍ᭴ᚑߔࠆC,H߿‫ޔ‬ᬀ‛ߩశวᚑ෻ᔕ߿
శ⸅ᇦ૞↪ߥߤ߽ⅣႺඨዉ૕ߣ᜛ᒛߒߡᬌ⸛ߒ‫㉄߿࠼ࡦࡕࡗࠗ࠳ޔ‬ൻ࠴࠲ࡦߩశ⸅ᇦ૞↪ࠍ೑↪ߒߚᄥ㓁㔚ᳰߥߤࠍ⠨᩺ߒߚ‫ޕ‬ᓥ᧪ߩᚑ⤑ᣇᴺߣߒߡߪએਅߩࠃ߁ߦᄢ೎ߐࠇ‫(ޔ‬1)Physical Vapor
Deposition :PVD ᴺ㧔⫳⌕㧘ࠬࡄ࠶࠲㧘࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦߥߤ㧕‫(ޔ‬2) Chemical Vapor Deposition㧦
CVDᴺ㧔ኈ㊂ᕈ㧘⺃ዉᕈ㧘⴫㕙ᵄ㧘ࡋ࡝ࠦࡦᵄ㧘ECRߥߤ㧕ߥߤᄙߊߩᬌ⸛߇ߥߐࠇߡ޿ࠆ‫ࠇߎޕ‬ࠄߩਛߢ‫ޔ‬ᐢࡃࡦ࠼ࠡࡖ࠶ࡊඨዉ૕ߩᚑ⤑ࠍ⋡ᜰߒ‫ޔ‬ಽሶᝄേߦ౒㡆ߔࠆ⥄↱㔚ሶ࡟࡯ࠩߣ㔚ሶബ⿠ࠍⴕ߁ࠛࠠࠪࡑ࡟࡯ࠩߩ㧞ࡈࠜ࠻ࡦࡊࡠ࠮ࠬߦࠃࠆࠕࡉ࡟࡯࡚ࠪࡦᴺࠍㆡ↪ߔࠆߎߣࠍᬌ⸛ߒ
ߚ‫ޕ‬‫⎇ޣ‬ⓥ᭎ⷐ‫ޤ‬㧝㧚㨚ဳDLC/pဳSiᄥ㓁㔚ᳰ
C6H6ߣC6H6㧗P(OCH3)ߩๆశశᐲ⸘ߦࠃࠆㅘㆊ₸᷹ቯߩ⚿ᨐ‫ޔ‬1600nm-1800nmߦ߆ߌߡC-H⚿วߦ⿠࿃ߔࠆๆ෼‫ߚ߹ޔ‬300nmએਅߦ߅޿ߡ߽శߩๆ෼߇⏕⹺ߐࠇߚ‫⚡ޔࠄ߆ߣߎߩߎޕ‬ᄖ஥ߩ200nm
એਅߩๆ෼ࠍ೑↪ߒ‫ޔ‬ArF૶↪ߒߚࠕࡉ࡟࡯࡚ࠪࡦ߇น⢻ߣߥࠅ‫ޔߚ߹ޔ‬C-H⚿วߩಽሶᝄേߦ⿠
࿃ߔࠆๆ෼Ꮺၞߢߪ‫ޔ‬FEL࡟࡯ࠩࠍ૶↪ߒߡᵄ㐳ࠍᄌൻߐߖࠆߎߣߦࠃࠅലᨐ⊛ߦࠕࡉ࡟࡯࡚ࠪࡦ
߇ⴕ߃ࠆߣ੍ᗐߢ߈ࠆ‫ޕ‬ታ㓙ߦFEL࡟࡯ࠩᵄ㐳ࠍC-H⚿วߩๆ෼Ꮺၞߢ޽ࠆ2.4Ǵmߦㆬᛯߒߡࠣ࡜
ࡈࠔࠗ࠻☳ᧃߣ಄ළ࿕૕ൻߒߚC6H6㧗P(OCH3)ߦᾖ኿ߒߚ‫ߪߦᤨ↪૶࠻࠶ࠥ࡯࠲ᧃ☳ޕ‬ၮ᧼⴫㕙ߦ⤑߇ᒻᚑߐࠇߚ߇‫ޔ‬ṁᶧ࠲࡯ࠥ࠶࠻૶↪ᤨߦߪ࠲࡯ࠥ࠶࠻⴫㕙ߦࠕࡉ࡟࡯࠻ߐࠇߚ∥߇⏕⹺ߐࠇߚ߇‫ޔ‬ᚑ⤑ၮ᧼਄ߦ⤑ߩᒻᚑߪ⏕⹺ߢ߈ߥ߆ߞߚ‫ࠍ࠻࠶ࠥ࡯࠲ᧃ☳ޕ‬FELߢ‫ޔ‬C6H6෸߮C6H6㧗P(OCH3
ࠍArFߢߘࠇߙࠇၮ᧼᷷ᐲࠍᄌൻߐߖߡࠕࡉ࡟࡯࡚ࠪࡦߒᚑ⤑ߒߚ‫ߩߎޕ‬DLC⤑ߩ㗼ᓸ࡜ࡑࡦࠬࡍ
-1ࠢ࠻࡞ߢ‫ޔ‬FELߢ૞⵾ߒߚ⤑ߪ⤑ෘ100nmߢ޽ࠅ‫ޔ‬1580cm ߦgraphitic (-G) band߇⏕⹺ߐࠇߚ‫ޕ‬-1

1580cm ߦgraphitic (-G) band‫ޔ‬1360cm-1ߦdisordered (-D) band߇⏕⹺ߐࠇ‫ޔ‬G/DᒝᐲᲧߪၮ᧼᷷ᐲࠍ
਄᣹ߐߖࠆߣૐਅߔࠆߎߣ߇⏕⹺ߐࠇߚ‫ޔߚ߹ޕ‬C6H6ࠍ૶↪ߒߚDLC⤑ߢߪG-band߇ࠤࡒࠞ࡞ࠪࡈ
࠻ߔࠆ੐߇⏕⹺ߐࠇߚ‫ޕ‬C6H6㧗P(OCH3)࠲࡯ࠥ࠶࠻ࠍArFߢࠕࡉ࡟࡯࡚ࠪࡦߒ‫ޔ‬ၮ᧼᷷ᐲ200͠ߢᚑ⤑ߒߚ⹜ᢱ߳⇼ૃᄥ㓁శࠍᾖ኿ߒߚߣ߈ߩ㔚࿶-㔚ᵹ․ᕈ߆ࠄ‫ޔ‬⍴⛊㔚ᵹ3.22ǴA㐿᡼㔚࿶0.17V⊒㔚

-5ല₸810 %ߩ಴ജ߇⏕⹺ߐࠇ‫ޔ‬㨚ဳDLC/pဳSiᄥ㓁㔚ᳰ߇ߢ߈ߚ‫ޕ‬㧞㧚 ⦡⚛Ⴧᗵဳ㉄ൻ࠴࠲ࡦᄥ㓁㔚ᳰ
100‫ޔ‬200͠ߢᚑ⤑ߒߚ⭯⤑ߢࠕ࠽࠲࡯࠯ဳTiO2ߦ․ᓽ⊛ߥ⚿᥏㕙ߩࡇ࡯ࠢߪ⏕⹺ߢ߈‫ޔ‬᷷ᐲ਄᣹
ߦ઻޿XRDࡇ࡯ࠢߩᒝᐲ߇ᄢ߈ߊߥࠅ⚿᥏ᚑ㐳ߒߡ޿ࠆߎߣ߇ಽ߆ࠆ‫ߒ߆ߒޕ‬300‫ޔ‬400͠ߢᚑ⤑ߒߚ⭯⤑ߢߎߩࡇ࡯ࠢߪ⏕⹺ߢ߈ߕࠕࡕ࡞ࡈࠔࠬߥ⤑⾰ࠍ␜ߔࡉࡠ࡯࠼ߥ․ᕈߣߥߞߚ‫ޕ‬એ਄ߩ⭯⤑ࠍ↪޿ߡTiO2⦡⚛Ⴧᗵဳᄥ㓁㔚ᳰࠍ૞⵾ߒߚ‫ޕ‬శࠍᾖ኿ߔࠆߎߣߦࠃࠅ⍴⛊㔚ᵹ୯߇Ⴧടߒᄥ㓁㔚ᳰߣߒߡశ㔚ᄌ឵ߒߡ޿ࠆߎߣ߿‫ޔ‬100͠߆ࠄ200͠ߣ᷷ᐲ਄᣹ߦࠃࠅ಴ജߩะ਄ߦ઻޿శ㔚ᄌ឵ല₸߇ะ਄ߒߡ޿ࠆߎߣ߇⏕⹺ߢ߈ࠆ‫ޕ‬㧟㧚 (LaO)CuS ⊒శ᧚ᢱArFࠛࠠࠪࡑ࡟࡯ࠩߢ૞⵾ߒߚ⭯⤑ߩࡈࠜ࠻࡞ࡒࡀ࠶࠮ࡦࠬ(PL)᷹ቯ⚿ᨐࠍ࿑㧣ߦ␜ߔ‫ߡߴߔޕ‬ߩᚑ⤑᧦ઙߦ߅޿ߡ380nmߩࠛࠠࠪ࠻ࡦ⊒శ߇⏕⹺ߐࠇߚ‫ޕ‬Ar㔓࿐᳇ߢ૞ᚑߒߚ⭯⤑ߦ߅޿ߡ‫ޔ‬ၮ᧼᷷ᐲࠍ਄᣹ߐߖߡ޿ߊߦߟࠇߡ600nmઃㄭߦ⷗ࠄࠇߚਇ⚐‛߿ᰳ㒱ߦࠃࠆࡉࡠ࡯࠼ߩࡇ࡯ࠢ߇
100͠ߩ႐วߪ‫ޔ‬700nmઃㄭߦ࡟࠶࠼ࠪࡈ࠻ߒߚࡇ࡯ࠢߣߒߡ⏕⹺ߐࠇߚ‫ޕ‬
㧠㧚PXRߦࠃࠆXAFS᷹ⷰᐢࡃࡦ࠼ࠡࡖ࠶ࡊ㉄ൻ‛ඨዉ૕ߦ߅޿ߡ㉄ൻߩ⒟ᐲ߿⓸ൻߥߤߦࠃߞߡࡈࠜ࠻࡞ࡒࡀ࠶࠮ࡦࠬ
․ᕈ߇ᄌൻߔࠆߎߣ߇⠨߃ࠄࠇ‫㉄ޔ‬ൻ߿⓸ൻߩቯ㊂ൻ߇㊀ⷐߢ޽ࠆ‫⤑ࡦ࠻ࡊࠞޕ‬਄ߦCuO⭯⤑ࠍࠛࠠࠪࡑ࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦᴺߢᚑ⤑ߒߚ‫ޕ‬㌃▗(ෘߐ20Ǵm)ࠍࠦࡦ࠻ࡠ࡯࡞ߣߒߡ⾍ઃߌ‫ޔ‬㌃▗ㇱಽ(Cu)ߩXAFSࠬࡍࠢ࠻࡞ࠍ᷹ⷰߒߚߣߎࠈ‫ޔ‬㕖ᏱߦṖࠄ߆ߥKࠛ࠶ࠫ․ᕈࠍ␜ߒߡ޿ߚ‫ࠩ࡯࡟ޕ‬ࠕࡉ࡟࡯࡚ࠪࡦߢᚑ⤑ߒߚCuOߩXAFSࠬࡍࠢ࠻࡞ߪ㉄ൻߩ⒟ᐲ߇ᄢ߈ߊߥࠆߦߟࠇߡ‫ޔ‬Kࠛ࠶ࠫߩ┙ߜ਄߇ࠅߣEXAFSᝄേߦᄌൻ߇⴫ࠇߚ‫ޕ‬‫ޤ߼ߣ߹ޣ‬
FELࠍ૶↪ߒߚࠕࡉ࡟࡯࡚ࠪࡦߢߪ࠲࡯ࠥ࠶࠻⴫㕙ߩ⎕უߪ⏕⹺ߐࠇߚ߇‫ޔ‬ᚑ⤑ၮ᧼਄ߦ⤑ߩᒻᚑߪ⏕⹺ߐࠇߥ߆ߞߚ‫ޕ‬C6H6㧗P(OCH3)ࠍArFߦࠃࠅၮ᧼᷷ᐲ200͠ߢᚑ⤑ߒߚߩ߽ߩߢߪ⍴⛊㔚ᵹ
-5

3.22ǴA㐿᡼㔚࿶0.17V⊒㔚ല₸810 %ߩ಴ജ߇ᓧࠄࠇࠆ㨚ဳDLC/pဳSiᄥ㓁㔚ᳰ߇ߢ߈ߚ‫㉄ޕ‬ൻ࠴2࠲ࡦߢߪTi:O߇1:1.7ߩᤨߦ㐿᡼㔚࿶0.53V‫ޔ‬⍴⛊㔚ᵹ 6.24 mA/cm ‫ޔ‬ല₸0.51%ߩTiO2⦡⚛Ⴧᗵဳᄥ㓁㔚ᳰߣߥߞߚ‫(ޕ‬LaO)CuSߢߪၮ᧼᷷ᐲߩ਄᣹߿O2㔓࿐᳇ߢߩᚑ⤑ߦࠃߞߡPLࠬࡍࠢ࠻࡞ߪࡃ࡞
ࠢߦᲧߴߡ࡟࠶࠼ࠪࡈ࠻ߒ‫⚵ޔ‬ᚑᲧߩ೙ᓮߦࠃߞߡPL⊒శߩᵄ㐳ߪนᄌߣߥࠆߎߣ߇᣿ࠄ߆ߣߥߞ
ߚ‫ޕ‬CuO⭯⤑ߩPXRߦࠃࠆXAFS᷹ⷰߩ⚿ᨐ‫ޔ‬Kࠛ࠶ࠫߩ┙ߜ਄߇ࠅߣEXAFSᝄേߦᄌൻ߇⴫ࠇߚ‫ޕ‬‫⎇ޣ‬ⓥᬺ❣╬‫ޤ‬࡮⊒⴫⺰ᢥ(1) M.ITOH, Y.SUDA, M.A.BRATESCU, Y.SAKAI, K.SUZUKI ‫ޟ‬Amorphous carbon nitride film
preparation by plasma-assisted pulsed laser deposition method ‫ޠ‬Appl. Phys., A79, pp.1575-1578(2004)(2) Y.SUDA, K.UTAKA, M.A.BRATESCU, Y.SAKAI, J.TSUJINO, K.SUZUKI ‫ޟ‬Growth of carbon
nanotubes on Fe or Ni-coated Si substrate by feeding with carbon from a graphite ablation plume ‫ޠ‬Appl. Phys., A79, pp.1331-1333 (2004)(3) ㋈ᧁ ⮍‫ࡦ࡚ࠪ࡯࡟ࡉࠕࠩ࡯࡟ޟ‬ᴺߦࠃࠆ⭯⤑↢ᚑߣߘߩ․ᕈ‫ޠ‬᡼㔚ቇળ⹹, Vol.47, pp.11-17,(2004)(4) T.ONO, Y.SUDA, M.AKAZAWA, Y.SAKAI, K.SUZUKI ‫ޟ‬Effects of Oxygen and Substrate
Temperature on Properties of Amorphous Carbon Films Fabricated by Plasma-Assisted Pulsed Laser
Deposition Method ‫ޠ‬J.J. Appl.Phys., Vol.41, pp.4651-4654 (2002)(5) Akira Mori, Kaoru Suzuki ‫ޟ‬High-Repetition Frequency Short Pulses in a VHF Discharge-Excited SlabType Carbon Dioxide Laser Using Ultrasonic Vibrator ‫ޠ‬Electrical Engineering in Japan, Vol.41, pp.1-7(2003)(6) ਛ᫪⑲᮸, ศ↰ੳ♿, ㋈ᧁ⮍ ‫ࠍࠬࠕࠗࡃࠬ࡞ࡄ⽶ޟ‬೑↪ߒߚࠗࠝࡦࡆ࡯ࡓ⫳⌕ᴺߦࠃߞߡ↢ᚑߒߚ࠳ࠗࡗࡕࡦ࠼⁁὇⚛⤑ߩ․ᕈ‫ޠ‬㔚᳇ቇળ⺰ᢥ⹹A, Vol.122A, pp.274-280 (2002)
࡮ቇળ⊒⴫(1) Kaoru Suzuki ‫ޟ‬Phosphorus doped diamond like carbon films deposited by plasma-assisted free electron
and ArF laser ablation method ‫ޠ‬Laser and Applications in Science and Engineering 5713C-88,
pp.41-46 (2005-1:San Jose)(2) ᷡ᳓ᵗᐔ㧘㜞ἑᶈ৻㧘㋈ᧁ⮍‫ࡑ࠭࡜ࡊޟ‬ᡰេ࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦᴺߦࠃࠆ㧔LaO㧕CuS ᚑ⤑‫ޠ‬㔚᳇ቇળశ࡮㊂ሶ࠺ࡃࠗࠬ⎇ⓥળ⾗ᢱ㧘OQD-05-02㧘pp.5-9㧘(2005.3: ർᶏ㆏ᄢቇ)(3) ↰ਛᘮᒾ㧘㋈ᧁ⮍‫ޟ‬RF ᡼㔚ᡰេ࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦᴺߦࠃࠆDLC ᄥ㓁㔚ᳰߩᚑ⤑‫ޠ‬㔚᳇ቇળ శ࡮㊂ሶ࠺ࡃࠗࠬ⎇ⓥળ⾗ᢱ㧘OQD-04-08㧘pp.41-46㧘(2004.3: ㊄ᴛᄢቇ)(4) ⋉↰ᕺᄥ㧘㋈ᧁ⮍‫ࡦ࡚ࠪ࡯࡟ࡉࠕࠩ࡯࡟ޟ‬ᴺߦࠃࠆ㉄ൻ࠴࠲ࡦᄥ㓁㔚ᳰ૞⵾‫ޠ‬㔚᳇ቇળశ࡮㊂ሶ࠺ࡃࠗࠬ⎇ⓥળ⾗ᢱ㧘OQD-04-10㧘pp.51-55㧘(2004.3: ㊄ᴛᄢቇ)(5) Ꮏ⮮ᥓᒾ㧘㋈ᧁ⮍‫ࡦ࡚ࠪ࡯࡟ࡉࠕࠩ࡯࡟ޟ‬ᴺߦࠃࠆDLC ᄥ㓁㔚ᳰߩഃ⵾‫ޠ‬㔚᳇ቇળ శ࡮㊂ሶ࠺ࡃࠗࠬ⎇ⓥળ⾗ᢱ㧘OQD-03-12㧘pp.5-10㧘(2003.3: ᐢፉᄢቇ)(6) ዊᨋ዁ᄥ㇢㧘㜞ἑᶈ৻㧘㋈ᧁ⮍‫ࡦ࡚ࠪ࡯࡟ࡉࠕࠩ࡯࡟ޟ‬ᴺߦࠃࠆLaOCuS ߩ⭯⤑ൻ‫ޠ‬㔚᳇ቇળ
శ࡮㊂ሶ࠺ࡃࠗࠬ⎇ⓥળ⾗ᢱ㧘OQD-03-15㧘pp.23-26㧘(2003.3: ᐢፉᄢቇ)ߘߩઁ‫ޔ‬㔚᳇ቇળో࿖ᄢળ࡮ᔕ↪‛ℂቇળᐕᰴᄢળ࡮࡟࡯ࠩ࡯ቇળᐕᰴᄢળߥߤߦ36 ઙ࡮ቇ૏ߩขᓧ⁁ᴫ(1) ዊᨋ ዁ᄥ㇢: ୃ჻(Ꮏቇ), ࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦᴺߦࠃࠆLaOCuS⭯⤑ߩ૞ᚑߣ․ᕈ⹏ଔ, 2004 ᐕ
2 ᦬, ᣣᧄᄢቇᄢቇ㒮ℂᎿቇ⎇ⓥ⑼㔚᳇Ꮏቇኾ᡹
(2) ↰ਛ ᘮᒾ: ୃ჻(Ꮏቇ), ࡊ࡜࠭ࡑᡰេ࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦᴺߦࠃࠆDLCᄥ㓁㔚ᳰߩᚑ⤑, 2005
ᐕ2 ᦬, ᣣᧄᄢቇᄢቇ㒮ℂᎿቇ⎇ⓥ⑼㔚᳇Ꮏቇኾ᡹

(3) ⋉↰ ᕺᄥ: ୃ჻(Ꮏቇ), ࡟࡯ࠩࠕࡉ࡟࡯࡚ࠪࡦᴺߦࠃࠆTiO2⦡⚛Ⴧᗵဳᄥ㓁㔚ᳰߩ૞⵾, 2005 ᐕ2
᦬, ᣣᧄᄢቇᄢቇ㒮ℂᎿቇ⎇ⓥ⑼㔚᳇Ꮏቇኾ᡹

Appl. Phys. A 79, 1575–1578 (2004)

Applied Physics A

DOI: 10.1007/s00339-004-2852-2

Materials Science & Processing

m. itoh1
y. suda1
m.a. bratescu1
y. sakai1,uk. suzuki2

Amorphous carbon nitride ﬁlm preparation byplasma-assisted pulsed laser deposition method
1 Graduate School of Engineering, Hokkaido University, North 13 West 8, Sapporo, 060-8628, Japan
2 Department of Electrical Engineering, College of Science & Technology, Nihon University 1-8-14,

Surugadai, Kanda, Chiyoda-ku, Tokyo, 101-8308, Japan

Received: 26 September 2003/Accepted: 26 March 2004
Published online: 26 July 2004 • © Springer-Verlag 2004
ABSTRACT Amorphous carbon nitride (a-CNx ) ﬁlms were prepared by pulsed laser ablation of graphite in N2 RF plasma.
The ﬁlm property was compared with that prepared in N2 gas.
The N2 plasma was generated by a mesh electrode, which wasinserted between a graphite target and a Si substrate. The gaspressure pN2 was varied from 10 to 100 mTorr. The ﬁlm deposition rate exponentially decreased with pN2 for both the plasmaand gas environment. X-ray photoelectron spectroscopy analysis showed that the ratio of nitrogen content to the carbon one([N]/[C]) of the a-CNx ﬁlm surface deposited in the N2 plasma
was ∼2 times higher than that obtained in the N2 gas. The ﬁlm
structure was shown by Raman spectroscopy analysis that sp2clustering was enhanced with increasing the [N]/[C]. The effectof plasma on a-CNx ﬁlm deposition was discussed.
PACS 81.15.Fg; 79.60.-i; 81.05.Uw

1

Introduction

Carbon nitride is a promising material for electronics and mechanical technology because of its excellent
physical properties, such as high hardness, low coefﬁcient offriction and high thermal conductivity. Since Liu and Cohen
predicted that β-C3 N4 could have a higher bulk modulus thandiamond [1], numerous studies for crystallization of carbon
nitride have been performed. So far, amorphous carbon nitride(a-CNx ) ﬁlm has been successfully synthesized by pulsed
laser deposition (PLD) and showed good mechanical as wellas an electron ﬁeld emission property [2, 3].
PLD in nitrogen gas atmosphere has many advantages
for a-CNx ﬁlm deposition, as: (1) energetic carbon species
generated in a plume promote sp3 C−C bonding, and (2) ambient nitrogen gas pressure can be varied in a wide range.
Moreover, plasma assisted PLD (PAPLD) technique is useful for getting a high ratio of nitrogen to carbon ([N]/[C])in a-CNx ﬁlms. Therefore, so far, many reports concerning
PAPLD of a-CNx ﬁlms have been presented, for instance,in [4–6]. However, almost of them employ “a remote plasma
technique”, which generates nitrogen ions, nitrogen atoms
u Fax: +81-11/706-7890, E-mail: sakaiy@eng.hokudai.ac.jp

and excited nitrogen molecules by plasma gun mounted awayfrom a substrate and makes them bombard the substrate topromote the chemical reactions between carbon and nitrogen in a-CNx ﬁlms [4, 5]. On the other hand, the author’sgroup has been studying PAPLD in a different electrode system from aforementioned one [7–9]. In the present system,
plasma was generated around a mesh electrode inserted in
the space between the substrate and the target. This system issimilar to that in [6]. We have elucidated advantages of thisPAPLD system, as: (1) carbon nanoparticle growth was enhanced in Ar plasma atmosphere because nanoparticles canbe positively and/or negatively charged in plasma and coalesce by Coulomb force [7, 8], (2) carbon species in a plumein oxygen plasma atmosphere could react with oxygen radicals while the plume was ﬂying [9], and (3) μm-sized droplets
ablated from a target could be expelled by the sheath electricﬁeld generated near the substrate and droplet free ﬁlms wereobtained [9].
In the present study, we demonstrated a-CNx ﬁlm deposition using a PAPLD method in nitrogen atmosphere, andevaluated the effect of the plasma on the ﬁlm properties. The
deposited a-CNx ﬁlms were analyzed by ellipsometry, X-ray
photoelectron spectroscopy (XPS) and Raman spectroscopy.
The physical property of the ﬁlm (deposition rate, [N]/[C],C−C bonding state) was examined.
2

Experimental

The present experimental setup of a PAPLD system is the same as that described in the previous reports [7–9].
Here, the essential points are brieﬂy described. An ArF excimer laser (LAMBDA PHYSIK COMPex 205; λ = 193 nm;
pulse duration = 20 ns) is used as ablation laser. The laser
beam is focused by two cylindrical lenses and irradiated tothe spot size of 1 mm × 5 mm on the target with an incident angle of 37◦ . The PAPLD chamber contains a substrate
and a target holder and is evacuated up to 2.7 × 10−6 Pa.
A mesh electrode (ϕ = 68 mm; mesh opening = 0.328 mm)
was inserted between the target and substrate. An RF ( f =13.56 MHz) plasma was generated around the mesh. The target and substrate spin with around 25 and 10 rpm, respectively. The target and substrate were pre-treated before thedeposition as described in the previous reports [7–9]. N2
gas (purity = 99.9995%) was introduced through a mass ﬂow

1576

Applied Physics A – Materials Science & Processing

TargetSubstrate
Laser ﬂuenceLaser repetition rate
Target-substrate distance
RF input power
TABLE 1Sintered graphite (purity = 99.999%)
n-type Si(100)3 J cm−2
10 Hz
37 mm
60 W

Experimental condition

controller with a ﬂow rate of 10 sccm. The N2 gas pressure
pN2 was kept to be at 10 – 100 mTorr. Deposition is continued
for 30 – 120 minutes at room temperature. The experimental
condition is listed in Table 1.
The ﬁlm thickness was measured by an ellipsometer(Mizojiri Optical Co., Ltd, DVA-FL3). The chemical composition and bonding state of the ﬁlm were analyzed by
X-ray photoelectron spectroscope (XPS: Shimadzu Cooperation, ESCA-3400; X-ray radiation: Mg K α (1253.6 eV); passenergy = 75 eV) and Raman spectroscope (JASCO Co. Ltd.,
NR-1000HS: excitation wavelength = 632.8 nm).

FIGURE 1

C (1s)
C−C
284.6 eV
TABLE 2

3

Results and discussion

The deposition rate of a-CNx ﬁlms as a function of
pN2 is shown in Fig. 1. The deposition rate exponentially decreased with pN2 . It is reasonable that ablated carbon clusters
are decelerated due to an increase of collisions with ambient
N2 gas molecules and cannot reach the substrate with increasing the pressure. There was no difference in the deposition
rate in the conditions of between N2 gas and N2 plasma. Generally, plasma generates high electric ﬁeld in sheath region
near the substrate surface, and then ionic carbon species (C+n)
may have high velocities. However, for the deposition rate
result, there was no difference between the N2 gas and N2
plasma conditions. It may indicate that the present magnitudeof sheath potential did not affect C+
n or most of the impinging
species are neutral.

Film deposition rate as a function of pN2

sp2 C−N
285.9 eVN (1s)
sp3 C−N
287.7 eVN−sp3 C
398.5 eVN−sp2 C
400.0 eV

BE of C−C and C−N bonds in C (1s) and N (1s) XPS spec-tra [7]The C (1s) and N (1s) XPS spectra of the a-CNx ﬁlms deposited in the N2 plasma are shown in Fig. 2. The binding
energies (BE) of C−C and C−N in XPS spectra were reportedby Marton, et al. [10] as listed in Table 2. With increasing pN2 ,the energy at which the C (1s) peak shows shifts from the BEof C−C to that of sp2 C−N, and the peak in the N (1s) spectrum shifts from BE of N−sp3 C to that of N−sp2 C. Figure 3
shows the ratio of nitrogen content to carbon one ([N]/[C]) ofa-CNx ﬁlms evaluated by the area of C (1s) and N (1s) spectrum under consideration of the relative sensitivity factor foreach element. The value of [N]/[C] increases, but gradually,
with increasing pN2 . From these results, the increase of nitrogen content in the ﬁlm with pN2 would be ensured.

C (1s) and N (1s) XPS spectra of thea-CNx ﬁlms deposited in the N2 plasma

FIGURE 2

ITOH et al.

Amorphous carbon nitride ﬁlm preparation by plasma-assisted pulsed laser deposition method

FIGURE 3[N]/[C] ratio in the a-CNx ﬁlm as a function of pN2

FIGURE 4 Emission spectrum generated by synergy effect due to interaction between N2 plasma and carbon plume (= I1 − I2 − I3 ). All the measurements were performed in pN2 = 5 Torr

Note that the [N]/[C] in the plasma is ∼ 2 times higher
than that in the gas. To investigate the effect of plasma, spectroscopic measurement of the carbon ablation plume and theN2 plasma has been performed in our laboratory [11, 12], inthe following three experimental conditions: (1) laser ablation of graphite in N2 plasma (spectral intensity, I1 ); (2) laser
ablation of graphite in N2 gas ( I2 ); (3) N2 plasma only ( I3 ).
Subtracting the emission intensity of I2 and I3 from I1 (= I1 −I2 − I3 ), we obtain the plasma effect on the plume as shownin Fig. 4. This ﬁgure clearly shows the increase of CN violet emission (388.34 and 421.60 nm) and decrease of C2 Swanone (468.02 and 516.52 nm) in the condition (1). This result
implies that introduction of the plasma induced some sort ofsynergy effect. It may be reasonable to consider that energetic electron (> 9.76 eV) generated in plasma dissociates N2
molecule into radicals and promote chemical reaction of CN
molecule formation. If CN molecules were directly depositedon a-CNx ﬁlm, the value of [N]/[C] could be ∼1. However,a plateau tendency for the [N]/[C] in the plasma condition
is obtained as ∼0.6. On the surface reaction during the ﬁlm
deposition, further study, for instance, etching of carbon bynitrogen ions, is needed.
Raman spectra of the a-CNx ﬁlms at various [N]/[C] ratios are shown in Fig. 5a. Generally, the visible Raman spectrum of a-C has two peaks, G and D, which lie at around1560 and 1360 cm−1 , respectively. Both peaks arise from sp2

FIGURE 51577

a Raman spectra of a-CNx ﬁlms, and b I(D)/I(G) vs. [N]/[C]sites [9, 13, 14]. In the present analysis, broad peak ranging
from ∼ 1300 to ∼ 1600 cm−1 was obtained. This is a typical
spectrum of a-C and a-CNx ﬁlms [9, 13, 14]. Though CN peakat ∼2200 cm−1 was not detected from the present a-CNx , itis reported that this peak could be usually detected using UV
excitation [10].
The Raman spectrum was deconvoluted by ﬁtting a Lorentzian proﬁle to G and D peaks, and then the ratio of D peakintensity to G peak one, I(D)/I(G), was calculated as shownin Fig. 5b. I(D)/I(G) increases with [N]/[C], and G peak
position always locates at ∼ 1560 cm−1 . As this tendency isreferred to a three-stage model proposed by Ferrari et al. [14],the domain size of graphite clusters would be increased as increasing the [N]/[C].
4Conclusion

We have deposited a-CNx ﬁlms by N2 plasmaassisted pulsed laser deposition. It was found that, comparing to the conventional PLD in N2 gas, the nitrogen content in the ﬁlm was enhanced by introduction of nitrogenplasma without any decrease in the ﬁlm deposition rate.
This enhancement was suggested by the increase of CN content in the plume in the N2 plasma condition, which wasproven from emission spectroscopic observation. The chemical bond between carbon and nitrogen was ensured by the1578

Applied Physics A – Materials Science & Processing

C (1s) and N (1s) XPS spectra. Raman spectroscopy analysis indicated the increase of graphite cluster size with increasing the ratio of nitrogen content to carbon one in theﬁlm.
ACKNOWLEDGEMENTS The authors are grateful to Professor
H. Sugawara and N. Sakura at Hokkaido Univ. for their helpful comment andspectroscopic measurement.

REFERENCES
1 A.Y. Liu, M. Cohen: Science 24, 841 (1989)
2 I. Alexandrou, I. Zergioti, M.J.F. Healy, G.A.J. Amaratunga, C.J. Kiely,
H. Davock, A. Papworth, C. Fotakis: Surf. Coat. Technol. 110, 147(1998)
3 E. Fogarassy, T. Szorenyi, F. Antoni, J.P. Stoquert, G. Pirio, J. Olivier,P. Legagneux, P. Boher, O. Pons-Y-Moll: Appl. Surf. Sci. 197–198, 316(2002)

4 C.Y. Zhang, X.L. Zhong, J.B. Wang, G.W. Yang: Chem. Phys. Lett. 370,
522 (2003)
5 M.E. Ramsey, E. Poindexter, J.S. Pelt, J. Marin, S.M. Durbin: Thin Solid
Films 360, 82 (2000)
6 V. Marotta, S. Orlando, G.P. Parisi, A. Santagata: Appl. Surf. Sci.
208–209, 575 (2003)
7 Y. Suda, T. Ono, M. Akazawa, Y. Sakai, J. Tsujino, N. Homma: Thin
Solid Films 415, 15 (2002)
8 Y. Suda, T. Nishimura, T. Ono, M. Akazawa, Y. Sakai, N. Homma: Thin
Solid Films 374, 287 (2000)
9 T. Ono, Y. Suda, M. Akazawa, Y. Sakai, K. Suzuki: Jpn. J. Appl. Phys.
41, 4651 (2002)
10 D. Marton, K.J. Boyd, A.H. Al-Bayati, S.S. Todorov, J.W. Rabelais:
Phys. Rev. Lett. 73, 118 (1994)
11 M.A. Bratescu, Y. Sakai, D. Yamaoka, Y. Suda, H. Sugawara: Appl. Surf.
Sci. 197–198, 257 (2002)
12 M.A. Bratescu, N. Sakura, D. Yamaoka, Y. Sakai, Y. Suda, H. Sugawara:
Appl. Phys. A, DOI: 10.1007/s00339-004-2645-7
13 A.C. Ferrari, S.E. Rodil, J. Robertson: Phys. Rev. B 67, 155 306 (2003)
14 A.C. Ferrari, J. Robertson: Phys. Rev. B 61, 14 095 (2000)

Appl. Phys. A 79, 1331–1333 (2004)

Applied Physics A

DOI: 10.1007/s00339-004-2765-0

Materials Science & Processing

y. suda1
k. utaka1
m.a. bratescu1
y. sakai1,uj. tsujino2
k. suzuki3

Growth of carbon nanotubes on Fe or Ni-coated
Si substrate by feeding with carbon
from a graphite ablation plume
1 Graduate School of Engineering, Hokkaido University, North 13 West 8, Kita-ku, Sapporo, 060-8628, Japan
2 Hokkaido Electric Power Co., Inc., 2-1 Tsuishikari, Ebetsu 067-0033, Japan
3 Department of Electrical Engineering, College of Science & Technology, Nihon University 1-8-14,

Surugadai, Kanda, Chiyoda-ku, Tokyo, 101-8308, Japan

Received: 26 Septmeber 2003/Accepted: 4 March 2004
Published online: 26 July 2004 • © Springer-Verlag 2004
ABSTRACT By feeding with carbon clusters from the ArF excimer laser (λ = 193 nm) ablation of graphite target, carbon
nanotubes (CNTs) were grown on Fe and Ni ﬁlms deposited on
SiO2 /Si substrates, which were set inside a quartz tube with Ar
gas pressure of 500 Torr operating at 1100 ◦ C. Optical emission
spectroscopic observation of the ablation plume of graphite and
Ni/Y catalyst was performed in the Ar gas for a pressure range
of 0–600 Torr at room temperature and 1000 ◦ C. The emission
band intensity of C3 ( Ã1 Πu ) at the distance of 2 mm from thetarget increased with increasing Ar gas pressure.
PACS 79.20.Ds; 81.07.De; 39.30.+w

know, only a few results have been reported by, e.g., Braidy
et al. [7] and the authors’ group [5].
On the other hand, plasma chemical vapour deposition(CVD) of CNTs using hydrocarbon gases as carbon feedstock
has been extensively studied because a large volume of CNTs
can be grown on metal-catalysed substrates with an aligned
and ordered structure [8].
In this report, we have grown CNT on Ni and Fe catalyticﬁlms deposited on Si substrates by feeding with carbon clusters from plumes generated by ArF laser ablation of graphite
as well as Ni/Y-catalyzed graphite target. Optical emission
spectra from the ablation plume in Ar gas were observed tounderstand what kind of excited species existed in the plume.
2

1

Introduction

As carbon nanotubes (CNTs) show unique structural and excellent electronic properties, they have been
widely studied for applications, such as ﬁeld electron emitters, electronic devices and hydrogen absorption. Among
several CNT-production techniques, a method of laser ablation of metal-catalyzed graphite is known to synthesize
single-wall CNTs in gas phase with high yield [1, 2]. In thistechnique, the growth process of CNTs is thought as follows.
(1) Firstly, carbon and metal catalyst are vaporized from target
surface by laser ablation and form high temperature plasma.
(2) As the plasma gradually cools by collision with ambient
gas atoms, the vaporized carbon and metal clusters condense
to liquid-phase nanoparticles. (3) Finally, when the temperature of nanoparticle drops down below the carbon-metal
eutectic temperature, Teu (e.g., Teu for C−Ni = 1326 ◦ C),
carbon atoms are separated out from the nanoparticles andform CNT [3, 4]. In order to understand the aforementioned
presumption more clearly, it is essential to generate smallsize carbon clusters and grow CNT by feeding with them.
Therefore, we have studied CNT growth in gas phase by
ArF excimer laser (λ = 193 nm) ablation of metal-catalyzed
graphite [5] since ArF excimer laser generates mainly small
carbon clusters (C+n , n = 1 − 3) [6]. However, concerning theuse of ultra-violet laser light for CNT growth, as far as weu Fax: +81-11/706-7890, E-mail: sakaiy@eng.hokudai.ac.jp

Experimental setup and procedure

A schematic diagram of the present experimental
set-up for CNT growth (SUGA Co., Ltd., AL039) is illustrated in Fig. 1. The set-up consists of a quartz tube of 60 mm
in inner diameter and 620 mm in length, an electrical furnace(360 mm length) operating at 1100 ◦ C, and an ArF excimer
laser (LAMBDA PHYSIK, COMPex 205: λ = 193 nm; pulse
duration = 20 ns; ﬂuence = 2 J/cm2 ; repetition rate = 50 Hz).
Inside the tube, a target was mounted at the center of the furnace and was spun at 40 rpm. The operating temperature T in
the span of ∼ 100 mm at the center of the furnace was 1100 ◦ C
and dropped gradually down to ∼ 700 ◦ C at the front end and∼ 800 ◦ C at the back end. Sintered graphite containing 1 at. %Ni and a minute amount of Y (Ni/Y/C target: TOYO TANSO
Co., Ltd.) and pure graphite (Kojundo Chemical LaboratoryCo., Ltd.) were used as targets. Using inductively coupledplasma mass spectrometry (ICP-MS: JOBIN YVON S.A.S,
JY38UL) of Ni/Y/C target, the concentration of Y was measured to be < 0.1 at. %. Both metals were used as catalyst for
CNT growth as performed in [9]. In the experiment, the quartz
tube was ﬁrst evacuated down to < 10−2 Torr by a rotary
pump and then heated up to T = 1100 ◦ C for 2 hours. Ar gas
with a ﬂow rate of 600 sccm was introduced from the windowside inlet and pumped out through a butterﬂy valve by a rotary
pump. The gas pressure was kept at 500 Torr. On SiO2 /Si substrates, Ni and Fe catalytic ﬁlms with a thickness of ∼ 350 nm
and ∼ 300 nm were respectively prepared by DC sputtering,and placed at +30 mm, −30 mm and −60 mm from the target surface (+: upstream of the Ar gas ﬂow, −: indicates

1332

Applied Physics A – Materials Science & Processing
FIGURE 1

downstream). The grown CNT was analyzed with a scanningelectron microscope (SEM: Hitachi, S-4300). Optical emission spectrum of the ablation plume generated from Ni/Y/C
target surface was observed by photonic multichannel analyzer (PMA: Hamamatsu, PMA-11 (300 – 800 nm)) with an
exposure time of 20 ms.
3

Results and discussion

3.1

CNT growth on metal-catalyzed substrates

Figure 2a and b shows the SEM micrographsof CNTs on Ni/SiO2 /Si and Fe/SiO2 /Si substrates placedat −30 mm when Ni/Y/C target was used. The diametersof CNTs on Ni/SiO2 /Si and Fe/SiO2 /Si substrates are∼ 150 nm and ∼ 80 nm, respectively. The number densityof CNTs on Ni/SiO2 /Si is ∼ 2 times higher than that on
Fe/SiO2 /Si substrate. Both CNTs are > 100 μm in length.
The present CNT diameter is a few times larger than that obtained in gas-phase growth (∼ 20 – 50 nm) [5]. When a graphite target without Ni/Y catalyst was used, the characteristics
of CNT ﬁgures did not show any difference from those obtained by the catalyzed target.
Huang et al. reported that the CNT diameter depended on
the catalyst ﬁlm thickness because the ﬁlm thickness strongly
correlated with the size of catalytic nanoparticle encapsulated in CNT [10]. On the Fe ﬁlm surface, as seen in Fig. 2b,nanoparticles are composed. Their sizes are ∼ 400 nm, whichis larger than the size of catalyst particle for the CNT of 80 nm
in diameter in [10]. The present large size of nanoparticles
may come from the thick Fe ﬁlm (∼ 300 nm). Concerning theactivation thickness of the catalyst ﬁlms, further investigationis needed.
Figure 2a shows that the CNTs contain catalyst particles intheir tips. However, the CNTs on Fe/SiO2 /Si substrate shown

Experimental setup for CNT growthin Fig. 2b do not seem to hold them. There are some differences in the diameter, the number density and the shape of the
tip of CNTs grown on between Ni/SiO2 /Si and Fe/SiO2 /Si
substrates. These results may indicate that the catalyst effectof Ni and Fe on CNT growth is different. In the case of theplasma CVD process using C2 H2 gas, it was reported that
Ni catalyst yielded higher growth rate and the larger diameter of CNT than Fe did [10, 11]. Lee et al. explained thisdifference by the fact that the diffusion coefﬁcient of carbon in bulk Ni (1.6 × 10−7 cm2 s−1 ) is higher than that in Fe(1.1 × 10−7 cm2 s−1 ) [11].
Though the substrates were placed at three different positions, CNTs were grown mainly at the edge of the substrateplaced only at −30 mm. As Sen et al. and Puretzky et al.
observed dynamics of carbon clusters (Cn ) generated froma metal-catalyzed graphite target by laser ablation, Cn initiallygoes against Ar gas ﬂow, then was pushed back, and ﬁnallydeposited at certain position downstream the target as forming CNT [3, 4]. Taking into account these observations, we
speculate that in the present CNT growth process ablated Cn
initially reached the substrate surface, and then dissolved into
the catalytic metal, and CNT was ﬁnally precipitated from thesaturated metal particle [1]. The position at −30 mm may beappropriate to have enough carbon feedstock from the graphite ablation plume.
3.2

Optical emission spectrum of ablation plume of
Ni/Y/C target

In order to investigate ablated species from Ni/Y/C
target, optical emission spectroscopy was performed in the
Ar gas pressures of 0 – 600 Torr at room temperature (RT) and1000 ◦ C as shown in Fig. 3. The background emission fromthe electric furnace was removed. The emission band of C2( A3 Πg ) and the emission lines of CII ( 2P 0 ), YI ( y 2D0 3/2 ),FIGURE 2 SEM micrographs of the CNT
grown on a Ni/SiO2 /Si and b Fe/SiO2 /Si substrate. The ﬁlm thickness of Ni and Fe was∼ 350 nm and ∼ 300 nm, respectively

SUDA et al.

Growth of carbon nanotubes on Fe or Ni-coated Si substrate by feeding with carbon from a graphite ablation plume 1333
FIGURE 3 Optical emission spectrum of thelaser ablation plume of Ni/Y/C target in the Ar
gas pressure range of 0–600 Torr at the temperature of RT and 1000 ◦ C

YII (z 1D20 ) and ArI (4 p[1/2, 3/2], 4 p[1/2, 3/2, 5/2]) weredetected, which were identiﬁed from [13]. The wide bandsof C3 ( Ã1 Πu ) were detected at 405 nm, 410 nm and 431 nm
as [14, 15] indicated. Ni was not observed in this spectrum
since the intense lines of Ni lie in UV region [13]. The emission intensity of C3 ( Ã1 Πu ) increased as the Ar pressure andthe temperature increased. For the atomic and ionic emission
lines of C, the emission intensity at 1000 ◦ C was ∼ 100 times
higher than that at room temperature, however, the structure in
the spectrum did not changed. The C3 ( Ã1 Πu ) emission bands
could give information about the formation of carbon clusters
in the ablation plume.
4

Conclusion

CNTs were grown on Ni and Fe-catalyzed SiO2 /Si
substrates set inside a quartz tube operating at 1100 ◦ C byfeeding with carbon from the ArF laser ablation plume ofgraphite. The number density and diameter of CNT dependedon Ni and Fe catalytic metals. The optical emission spectroscopy of the ablation plume showed that carbon species
including the catalyst metal with various excited levels weregenerated by the laser ablation.
ACKNOWLEDGEMENTS The authors would like to thank Professor H. Sugawara, Mr. A. Okita and T. Kojima at Hokkaido Univ. for theirhelpful comments and advice. This research was supported in part by 21st
century COE program, “Meme-Media Technology Approach to the R&D of
Next-Generation Information Technologies” by MEXT, Japan and REFEC(Research Foundation for the Electrotechnology of Chubu), Japan.

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J. Chem. Phys. 108, 10 129 (1998)Jpn. J. Appl. Phys. Vol. 41 (2002) pp. 4651–4654
Part 1, No. 7A, July 2002
#2002 The Japan Society of Applied Physics

Eﬀects of Oxygen and Substrate Temperature on Properties of Amorphous Carbon Films
Fabricated by Plasma-Assisted Pulsed Laser Deposition Method
Tomoyuki O NO1 , Yoshiyuki SUDA1 , Masamichi A KAZAWA1 , Yosuke S AKAI1 and Kaoru SUZUKI2
1
2

Graduate School of Engineering, Hokkaido University, North 13 West 8, Sapporo 060-8628, Japan
Department of Electrical Engineering, College of Science and Technology, Nihon University, Tokyo 101-8308, Japan(Received December 6, 2001; revised manuscript received March 8, 2002; accepted for publication March 19, 2002)

Amorphous carbon (a-C) thin ﬁlms were deposited on Si (111) substrates by an oxygen RF plasma-assisted pulsed laser
deposition (PLD) method at an oxygen pressure of 53 mPa, as well as in vacuum and oxygen gas ambient at 53 mPa forcomparison, at substrate temperatures (Tsub ) between room temperature and 480 C. An X-ray photoelectron spectroscopy(XPS) analysis showed that the highest sp3 content of the ﬁlm was 58% in oxygen plasma PLD at Tsub ¼ 410 C. Under thiscondition, the ﬁlm surface morphology was shown to be quite smooth with a roughness of about 5 nm, by scanning electron
microscopy (SEM) and atomic force microscopy (AFM). Eﬀects of the oxygen plasma and the substrate temperature on theﬁlm properties were examined. [DOI: 10.1143/JJAP.41.4651]
KEYWORDS: amorphous carbon (a-C), pulsed laser deposition (PLD), oxygen plasma, substrate temperature, XPS, SEM,
Raman spectroscopy, graphite, diamond

1.

Introduction

Mirror

It is well known that amorphous carbon (a-C) ﬁlms have
many useful properties such as mechanical hardness, opticaltransparency near the infrared (IR) range, high thermal
conductivity, high electrical resistivity, low frictionalcoeﬃcient and chemical inertness.1) Therefore, a-C ﬁlms
will be widely used in ﬁelds of industrial coatings,
tribological materials and corrosion protection. The ﬁlm
consists of two components, that is, diamond (sp3 -bonded
carbon) and nondiamond. The sp3 -bonded/non-sp3 -bonded
carbon ratio, which depends strongly on the preparation
conditions, inﬂuences the aforementioned physical andchemical properties of a-C ﬁlm.2–8)
Pulsed laser deposition (PLD) is an excellent method forthe fabrication of a-C ﬁlms, because it can generate highly
energetic carbon clusters on a substrate. Consequently,
diamond-rich ﬁlms are obtained at relatively low substratetemperatures.9) However, particularly when laser beams withlong wavelengths are used, micrometer-sized droplets arealso deposited on the ﬁlm, which is undesirable for industrial
applications.
In plasma-enhanced chemical vapor deposition (PECVD)
of a-C ﬁlms, atomic oxygen generated by electron impact
dissociation is known to remove the nondiamond component
and hence to cause selective diamond component growth.8)
In PLD, as well, when oxygen is introduced into a reactor, it
is reported that atomic and excited oxygen enhances
diamond formation.10,11) In oxygen-plasma-assisted PLD,
since much atomic and excited oxygen is produced, selective
growth of the diamond component may be expected.
In the present study, we deposit a-C ﬁlms by a PLD
method carried out in oxygen RF plasma ambient. The ﬁlm
properties are analyzed by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy (XPS), atomic
force microscopy (AFM) and Raman spectroscopy. The
eﬀects of the oxygen plasma and substrate temperature on
the ﬁlm properties are examined.
2.

Experimental Setup and Procedure

The experimental setup is illustrated in Fig. 1. A focused
ArF excimer laser beam was irradiated onto a sintered

TMP

Substrate
Focusing Lens

TargetO2

RF Coil Mirror
Chamber

ArF
Excimer
LaserShield Box

Fig. 1. Schematic diagram of the experimental setup.

Table I.

Experimental condition.

Ablation laser:

ArF excimer laser (193 nm, 20 ns)

Laser ﬂuence:

2.1 J cm2

Repetition rate:

20 Hz

Target (purity):
Base pressure:

Graphite (99.999%)<6:5  104 Pa

Ambient gas (pressure):
Substrate:
Substrate temp. Tsub :Oxygen (53 mPa)
Si (111)
RT–480 C

Target–substrate distance:

33 mm

Plasma input power:

0, 20 W

Deposition time:

30–60 mingraphite target. A radio frequency (RF) plasma was
generated in a RF coil. Carbon ﬁlms were deposited on Si(111) substrates in vacuum, in 53 mPa oxygen gas and in
53 mPa oxygen plasma. Experiments were attempted at otherpressures up to 20 Pa, but no deposition occurred. The
pressure of 53 mPa was found to be favorable for revealing
the diﬀerences among the present three ambients. The
typical deposition rates in vacuum, oxygen gas and oxygen
plasma at a substrate temperature (Tsub ) of 400 C were about
1.5, 1.3 and 0.7 nm/min, respectively. Table I shows thepresent experimental conditions.
In an XPS (X-ray source: Mg K (1253.6 eV); passenergy: 75 eV) analysis of the ﬁlm, we referred to Au spectra
to calibrate the binding energy of C (1s). Gold spots were

4651

4652

Jpn. J. Appl. Phys. Vol. 41 (2002) Pt. 1, No. 7A

T. ONO et al.

Table II. Decomposing data of C (1s) spectra.
FWHM (eV)Peak position (eV)Diamond
Graphite

1.1
1.1

285.5
284.1

Intensity [arb. units]

Content

(a)

(a)
(b)

(b)

288 287 286 285 284 283 282 281

Binding energy [eV]Fig. 2. C (1s) spectra. (a) Polycrystalline diamond ﬁlm deposited byplasma CVD, and (b) crystalline graphite.

deposited by vacuum evaporation in some small areas (100 m) on the ﬁlm before the analysis. The binding energyof Au (4f ) was 83.57 eV using the present XPS instrument.
The C (1s) spectra were decomposed into ‘‘diamond(100% sp3 carbon)’’, ‘‘graphite (100% sp2 carbon)’’ and‘‘unidentiﬁed’’ components using the peak values and fullwidths at half maxima (FWHMs) listed in Table II. These
data were obtained from the spectra of polycrystalline
diamond (pc-diamond) (Kobe Steel Ltd.) and crystalline
graphite (c-graphite) samples obtained using the present
XPS instrument shown in Fig. 2.
3.

Results and Discussion

3.1 Morphology of ﬁlm surface
Figure 3 shows SEM micrographs of the ﬁlms depositedin (a) vacuum, (b) oxygen (O2 ) gas and (c) O2 plasma at an
O2 pressure pO2 of 53 mPa at Tsub  400 C. As is clearly
seen, the surface morphology of the ﬁlm formed in vacuum
and in O2 gas is rough. In particularly, about 300-nm-sizedparticles are seen on the ﬁlm prepared in the O2 gas. In
contrast, the ﬁlm surface obtained in the O2 plasma is quitesmooth.
PLD in gas ambients is well known as a fabrication
technique of ﬁne particles, particularly nm-sized particles(nanoparticles).12) Here, it is thought that ablated atoms andmolecules cool due to collisions with ambient gas atoms
and/or molecules and condense into nanoparticles. In O2 gas
ambient, ﬁne carbon particles with a diameter of 100 nm
were formed, as shown in Fig. 3(b). On the other hand, on
the ﬁlm deposited in O2 plasma no 100-nm-order particles
are seen, even at the same pO2 as in the case of O2 gas [seeFig. 3(c)]. In order to examine whether the plasma inhibited
particle formation in the ablation plume or on the ﬁlm(c)Fig. 3. SEM micrographs of the ﬁlms deposited at Tsub  400 C in (a)vacuum, (b) 53 mPa oxygen gas and (c) 53 mPa oxygen plasma.

surface, the carbon ﬁlm prepared in O2 gas [e.g., the ﬁlm
shown in Fig. 3(b)] was exposed to oxygen plasma for
30 min (¼ deposition time) using the same arrangement of
the coil, target and substrate as in the experiment resulting in
Fig. 3(c). However, the 100-nm-order particles remained
without any appreciable change in size. This result suggeststhat the smooth ﬁlm surface was not treated directly with O2
plasma, but O2 plasma restrained the formation of 100-nmorder particles in the plume, and/or did not allow theparticles to reach the substrate if they were generated in theplume. These speculations may be supported also by thefollowing ﬁndings. (1) In O2 plasma, atomic and reactive
oxygen, which are produced in signiﬁcant amounts byelectron collision, may etch the graphite component8) in theplume. (2) As in dense SiH4 plasmas, 100-nm-sizedparticles are formed with negative charge,13) and thesenegatively charged particles may not reach the substrate due
to a strong electric ﬁeld formed in the plasma sheathsurrounding the substrate.
Figure 4 shows an AFM image of the ﬁlm surface shownin Fig. 3(c). The imaged area is 1 m  1 m. It is clearlyshown that nanometer-scale ﬁne convex structures cover theJpn. J. Appl. Phys. Vol. 41 (2002) Pt. 1, No. 7A

T. ONO et al.

Oxygen plasma50

sp 3 content [%]4653

OxygenVacuum

40
30
20
10

Fig. 4. AFM image of sample shown in Fig. 3(c).

0entire surface of the ﬁlm. These convex structures are notformed by deposition of ﬁne nanoparticles grown in theplume, but are composed of migrated C clusters which
impinged into the ﬁlm subsurface since this surface wasprepared at 400 C.14)
3.2 Film Composition
Figure 5 shows C (1s) XPS spectra of the ﬁlms obtained ingraphite

Intensity [arb. units]

diamond

450 C
440 C
420 C
410 C
400 C

380 C

288

286 284282

Binding energy [eV]Fig. 5. C (1s) spectra of the ﬁlms in oxygen plasma at pO2 ¼ 53 mPa.

100

200

300

400

500

Substrate temperature [ C]
Fig. 6. sp3 content as a function of the substrate temperature.

the O2 plasma PLD at Tsub between 380 C and 450 C. At
Tsub  410 C, the peak binding energy (BE) of the ﬁlm isclose to that of [pc-diamond] (BE ¼ 285:5 eV). However,
above 420 C, the BE approaches that of c-graphite(BE ¼ 284:1 eV).
Figure 6 shows the sp3 content of the ﬁlms as a function of
Tsub . In vacuum and in O2 gas ambient, the sp3 content
decreases gradually with the increase of Tsub and noappreciable diﬀerences are seen. However, in the O2 plasma,
although the sp3 content decreases with Tsub below 100 C, it
increases with Tsub and ﬁnally reaches a maximum value of
58% at Tsub ¼ 410 C. For Tsub > 410 C the sp3 content
rapidly drops with Tsub . Above 450 C the sp3 content
becomes only a 2–3% in any ambient.
It is diﬃcult to explain why the distinct peak of the sp3
content appears at Tsub ¼ 410 C in O2 plasma PLD.
However, the following previously reported results will
help us to understand this peak. 1) In the microwave plasmaenhanced CVD experiment, the sp3 bond number decreases
with increasing Tsub , and addition of O2 gas signiﬁcantly
inﬂuences the growth of diamond ﬁlms below 500 C,
through the etching of nondiamond carbon component with
O and active species.8) Another example is the oxidizationeﬀect observed at around 500–600 C.11) 2) Deposition of aC from appropriate energy ion beams (100 eV) promotes
sp3 bonding,7) so the plasma sheath could accelerate Cþ
n tothe appropriate energy. 3) The deposition rate of the ﬁlms inO2 plasma PLD was signiﬁcantly lower than that in otherambients at Tsub  400 C. This may indicate selective
etching of nondiamond carbon components.8)
Based on the results presented above, we conclude thatappropriate energy impinging onto the substrate for Cþn due
to sheath formation was obtained in O2 plasma PLD at
410 C. More eﬃcient etching of nondiamond components
would shift the favorable Tsub for O2 addition in PLD or
CVD.8,11)Figure 7 shows Raman spectra of the ﬁlms deposited in (a)vacuum, (b) oxygen gas and (c) oxygen plasma of 53 mPa at
Tsub ¼ 410 C. The spectra in Figs. 7(a) and 7(b) clearlyshow two peaks at 1590 cm1 (indicating c-graphite G)

Jpn. J. Appl. Phys. Vol. 41 (2002) Pt. 1, No. 7A

T. ONO et al.

(1) The ﬁlm surface deposited in oxygen plasma of 53 mPa
was composed of namometer-sized particles, although
on the surface prepared in oxygen gas, particles withdiameters of approximately 300 nm were grown.
(2) The maximum sp3 content of the ﬁlm was 58% in theoxygen plasma at Tsub ¼ 410 C, though the sp3 content
deposited in vacuum and O2 gas decreased monotonically with the increase of Tsub below 450 C.
(3) The Raman spectra of the ﬁlm obtained in the oxygen
plasma at Tsub ¼ 410 C exhibited a typical amorphous
carbon property, although the ﬁlms deposited inoxygen and vacuum ambients were of a typical glassy
carbon.

(a)

Intensity [arb. units]

4654

(b)

(c)

Acknowledgements

1000 1200

1400

1600 1800

Raman shift [cm-1]
Fig. 7. Raman spectra of the carbon ﬁlms deposited in (a) vacuum, (b)oxygen and (c) oxygen plasma of 53 mPa at Tsub of 410 C.

and 1350 cm1 (indicating disordered nanometer-sizegraphite D). This structure represents a typical property ofglassy carbon.15) The G peak originates in lattice vibrationsin the crystal face, and the D peak originates in crystalline
graphite with nanometer size. The appearance of the D peakindicates disordered graphite. When the defects in the
crystalline graphite increase and their size is reduced below
2 nm, the intensity of the D peak starts to decrease.6) Hence,
the Raman spectra of a-C show broad peaks, andconsequently, Fig. 7(c) corresponds to the a-C spectra.
These results appear to be consistent with those obtained
from the XPS analysis.
4.

Conclusions

Amorphous carbon thin ﬁlms on a Si (111) substrate wereprepared by an oxygen-plasma(53 mPa)-assisted PLD
method and were compared with those prepared in vacuum
and oxygen gas (53 mPa). Eﬀects of the oxygen plasma andsubstrate temperature on the sp3 bonding content were
examined. The results are summarized as follows.

The authors are grateful to Professor H. Sugawara and Dr.
M. A. Bratescu at Hokkaido University, and Drs. J. Tsujino
and N. Homma at Hokkaido Electric Power Company for
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