化学気相成長（CVD）法によるカーボン薄膜の成長制御
吉村雅満
豊田工業大学 表面科学研究室
yoshi@toyota-ti.ac.jp
R. Tiwari, 鈴木誠也, 松岡佑樹, D. Nguyen

１．カーボンナノチューブーグラフェン複合体
２．グラフェン	

Background	  &	  MoJvaJon	  	  	  	  	  	  	Discovery	  of	  Nano	  Carbons	

1985	  	  1991	  	  1993	  	  2004	  	  2008	  	  Fullerene1	  MWCNT*2	  SWCNT3	  Graphene4	  （Krotoら）	

（Iijima）	

（Iijima）	

（Novoselov）	

CNT-­‐Graphite	  Composite5	  （Kondo）	

* CNT: carbon nanotube(1) H. W. Kroto et al., Nature, 318 (1985) 162. (2) S. Iijima, Nature, 354 (1991) 56.
(3) S. Iijima and T. Ichihashi, Nature, 363 (1993) 603. (4) K. S. Novoselov et al., Science, 306 (2004) 666.
(5) D. Kondo et al., Appl. Phys. Express, 1 (2008) 074003.

Background	  &	  MoJvaJon	  Physical	  Proper@es	
Ther	  cond	
熱伝導率

材料
Materials	

E	  c導電率	 
ond	 S /m

電流密度	 
current	
A /cm 2グラフェン
Graphene	108

108～5000

単層C
NT
SWCNT	

106-107109～3500

多層C
NT
MWCNT	

104-～3000

銀
Silver	6.8×107-428

銅Copper	

6.5×107

106

403

Aluminum	
アルミニウム4.0×107-236

W /(m ・K)

• Excellent	  electric	  and	  thermal	  conducJvity	  properJes	  of	  the	  composite,	  consisJng	  of	  graphenes	  and	  carbon	  nanotubes	  are	  expected	  ApplicaJon:	  Via-­‐hole	  wiring	  of	  electronic	  circuitry,	  etc	  Background	  &	  MoJvaJon	  Composite	  structure	  ﬁrst	  revealed	  by	  Kondo5	
Graphene	  layer5	

MWCNT5	
Scanning	  Electron	  Microscope	  Transmission	  Electron	  Microscope	  (5) D. Kondo et al., Appl. Phys. Express, 1 (2008) 074003.
*SEM: scanning electron microscopy **TEM: transmission electron microscopy

Background	  &	  MoJvaJon	  Composite	  structure	  revealed	  by	  Kondo5	
Interface	  between	  surface	  graphene	  and	  CNTs5	

Catalys
Scanning	  Electron	  Microscope	  Transmission	  Electron	  Microscope	  Catalyst	  parJcles	  on	  the	  Jp	  of	  CNT	(5) D. Kondo et al., Appl. Phys. Express, 1 (2008) 074003.
*SEM: scanning electron microscopy **TEM: transmission electron microscopy

Model	  of	  composite	  by	  Kondo5	  Background	  &	  MoJvaJon	  CVD	  growth	  of	  carbon	  ﬁlms	few	  nm	  CNT

600-­‐900	  °C	  Cat	  acJvaJon	   CNT	  growth	  Carbon	  source	  C	C	 C	cat	cat	  	  few100	  nm	  ~	  few	  µm	  cat	Graphene	  	  	  	  	  600-­‐1000	  °C	  Cat	  acJvaJon	  Carbon	  source	   precipitaJon	
C	C	 C	graphene	cat	sub		In-­‐situ	  TEM	  observaJon11	cat	

2.1~3.6 nm	

Cat	  acJvaJon	  Carbon	  source	   precipitaJon	
C	C	 C	graphite	cat	sup	sub	(5) D. Kondo et al., Appl. Phys. Express, 1 (2008) 074003.

granulaJon	  CNT	  growth	  Background	  &	  MoJvaJon	  Ques@on	  about	  the	  previous	  model	
How	  is	  carbon	  supplied	  into	  the	  catalyst	  under	  the	  graphite	  layers?	

•In	  the	  Kondo’s	  model,	  the	  catalyst	  is	  covered	  with	  graphite	  and	  CNTs	

•Catalyst	  loses	  its	  acJvity	  when	  covered	  with	  amorphous	  carbon	  or	  graphite13	  Kondo’s	  model	  Cat	  acJvaJon	  Carbon	  source	   precipitaJon	
C	C	 C	graphite	cat	(13) K. Hata et al., Science 306 (2004) 1362.	

granulaJon	  CNT	  growth	  Carbons	  From	  	  Where?	

Background	  &	  MoJvaJon	  Ideal	  vs.	  Real	  Structure	Surface	  Graphite	  Layers5	Flat,	  higher	  	  Ordered	  Graphite	

Noncon@nuous	  	  (turbostra@c	  )	cat	Structure	  of	  Surface	  Graphite	  	  Model	  proposed	  by	  Kondo5	  SEM	  by	  Kondo	

Our	  AFM	  image	

Rough	  par@cle-­‐like	  morphology	
(5) D. Kondo et al., Appl. Phys. Express, 1 (2008) 074003.

* AFM: atomic force microscopy	Eﬀect	  of	  Catalyst	  Materials	  (Fe,	  Co)	  How	  carbon	  atoms	  go	  into	  the	  surface	  graphite	  layer?	
assumpJon：

IniJal	  growth	  of	  composite	

Defects	  in	  the	  graphite	  layers	  have	  role	  as	  a	  path.	  

Many carbon

Few carbon

cat	  cat	sub	graphite	

Low crystallinity•High crystallinity

The	  crystal	  quality	  of	  surface	  graphite	  layers	  supposed	  to	  aﬀect	  the	  growth	  of	  composite	  Eﬀect	  of	  Catalyst	  Materials	  (Fe,	  Co)	  How	  the	  carbon	  go	  into	  the	  surface	  graphite	  layer?	
assumpJon：

defects	  in	  the	  graphite	  layers	  have	  role	  Many carbon can go

Few carbon can go

The	  purpose:	  • IniJal	  To	  clarify	  cat	  the	  carbon	  supply	  path	  into	  the	  growth	  cat	of	  composite	underlying	  graphite	sub	 layers	  Lowcrystalinity
High crystalinity• To	  clarify	  the	  growth	  model	  of	  composites	
Fe108	Co108	ü Crystallinity	  of	  precipitated	  carbon20	  – Fe:	   ﬁve-­‐	  and	  seven-­‐membered	  rings	  – Co： high	  quality	  	  	  Ø Comparison	  between	  Fe	  and	  Co	  catalyst	  (20) Y. Shibuta and S. Maruyama, Comp. Mater. Sci., 39 (2007) 842.

Graphite	  precipitaJon20	  (Shibuta’s	  simulaJon)	

Experimental	  Methods	

Experiment	cat	support	substrate	

Intensity [arb. unit]	

p Substrate	  • SiO2(50	  nm)/Si	  	  	  	  	  	  • Suppor@ng	  layers: 	  Al2O3 	  	  	  RF-­‐spuferig（Al2O3	  target）	  	  	  • catalyst:	  Fe,	  Co	  – Arc-­‐plasma	  deposiJon	  ※	  thickness	  measurement	  by	  AFM	  （precision：	  ±0.1	  nm）	  Raman	  Spectroscopy	

D	wavelength：532 nm
G	1200 1300 1400 1500 1600 1700	  	  Raman shift [cm-1]	

D:	  defect-­‐related	  peak,	  G:	  graphite	  peak	IG/ID: estimate of crystallinity	
M. S. Dresselhaus et al., Phys. Rep., 409 (2005) 47.

Experimental	  Methods	p Alcohol	  thermal	  Chemical	  Vapor	  DeposiJon	  (CVD)	  • Carbon	  source： 	  alcohol（ethanol）	  ※C2H2	  has	  been	  previously	  used	  • Custom-­‐made	  apparatus 	  	  	  	  Alcohol	  	  creaJon	  TG

PG

CVD

3 min 30 s

10 minPressure in chamber (torr)

growth	Temperature of substrate (°C)

Gas-­‐ﬂow	  control	Time(min)

TG: growth temperature (670°C)
PG: growth pressure (150 torr)

Experimental	  Methods	

•CVD	  growth	  of	  CNT	  by	  Alcohol	  CVD	  Cross-­‐secJonal	  SEM	  image	  30 µm

500 nmheater	  	  	  	  *	  cat:	  Co,	  thickness:	  2.0	  nm,	  Temp	  800C,	  Pressure	  310	  torr,	  5	  min	  growth	  300 µm

Eﬀect	  of	  Catalyst	  Materials	  (Fe,	  Co)	  Growth	  of	  Carbon	  Films	  from	  Fe	  and	  Co	Co	Fe		  	  	  		  	CNT	  ••	  	  	  	Inter	  composite	  Composite	  growth	  at	  thinner	  region	  for	  Co	  than	  Fe	  Graphite	  formaJon	  at	  thick	  Co	  Eﬀect	  of	  Catalyst	  Materials	  (Fe,	  Co)	  Crystallinity	  of	  composites	  grown	  from	  Fe	  and	  Co	Fe	Co	L	  

1.3
1.2
1.1

1.5
1.4

0.9

0.8

0.83.5Co	  precipitates	  higher	  quality	  of	  graphenes	

1.1

0.9

2.5

Crystallinity：Raman	  (IG/ID)	  	  	  Fe	  (0.79)	  ＜Co	  (1.05)	  ü 	  Consistent	  with	  the	  Shibuta’s	  study	  

1.2

1.0

1.5	  	  1.3

1.0

0.7

•

Inter FeX
tals’	  Q	  

1.4

IG/ID

H	  

Intermediate Co

1.5graphite（Co）
鉄Fe	  コCo	バルト

0.7
7 9 11 13 15 17
4.5 5.5

thickness [nm]	  	  	  		  	CNT	  	  	  	  	Inter	  composite	  Eﬀect	  of	  Catalyst	  Materials	  (Fe,	  Co)	  Growth	  at	  thick	  catalyst	  region	

••Fe	  

CNT	  arrays	  under	  the	  graphite	  for	  Fe	  No	  CNT	  arrays	  under	  the	  graphite	  for	  Co	  Co	  15.8 nm

4.6 nmFe	Co	
20 µm	

Composite	  formaJon	

20 µm	

Graphite	  formaJon	

Eﬀect	  of	  Catalyst	  Materials	  (Fe,	  Co)	  Defect	  in	  Graphite	  is	  path	  or	  not?	

IniJal	  stage	

Fe： composite

Co：graphite	  Many Carbon

Few carbon

Fe	  Co	graphite	

Low crystallinity
Fe	High crystallinity

Co	

CNT growth

No CNT

composite	  graphite	  Graphite	  defects	  is	  PATH	  of	  carbons	  Background	  &	  MoJvaJon	  Real	  Structure	  of	  the	  composites	
disordered	rough	Surface	  graphite	Flat,	  higher	  	  ordered	  HOPG	

cat	cat	Model	  proposed	  by	  Kondo5	  CNT	Our	  proposed	  structure	  Conclusions	  	p Effect of Catalytic Material to the Synthesis of Graphite-capped
Vertically Aligned Carbon Nanotube Arrays•••

Iron	  catalyzed	  aligned	  CNT	  arrays	  at	  the	  overall	  thickness	  (2.0	  ~	  15.8	  nm	  for	  CNT	  arrays	  ~	  composite),	  while	  cobalt	  catalyst	  lost	  its	  acJvity	  to	  synthesize	  aligned	  CNT	  arrays	  above	  4.6	  nm.	  	  CrystalliniJes	  of	  the	  CNTs	  arrays	  synthesized	  from	  thin	  iron	  and	  cobalt	  ﬁlm	  were	  compared	  by	  Raman	  spectroscopy.	  The	  Co–catalyzed	  CNTs	  showed	  befer	  crystallinity	  than	  Fe-­‐catalyzed	  ones	  (GD	  raJo:	  1.05	  and	  0.79	  for	  cobalt	  and	  iron,	  respecJvely).	  	  Based	  on	  these	  results,	  defects	  in	  the	  graphiJc	  forms	  are	  assumed	  as	  paths	  of	  the	  carbon	  supply	  to	  the	  catalyst.	  Since	  the	  cobalt	  catalyst	  precipitates	  higher	  crystalline	  graphite	  than	  iron,	  the	  cobalt	  deacJvates	  quickly	  because	  of	  suppression	  of	  carbon	  supply,	  resulJng	  in	  the	  formaJon	  of	  graphite	  ﬁlm.	

グラフェンの特性	
・高移動度(2×105 cm2/V・s)
1000cm2/V・s for Si
・0.3µm弾道電子・スピン伝導・熱伝導度およびヤング率が大きい
・高光透過率(97.7%)・低欠陥濃度(~1x1010cm-2)

グラフェンのエレクトロニクスを中心とした応用	
デバイス機能（基礎物理）	
電子（n, p; 高移動度、零ギャップ、面配線・・・）	
スピン（高スピン拡散、ジグザグエッジスピン、・・・）	
光（ノン・ボルン・オッペンハイマー、・・・）	
電子源（・・・）、複合材料（強度、導電性、・・）	

材料（基礎物性）	

デバイス作製	

作製・成長技術	
単層、複数層、基板	サイズ、集積化（均一性）	
（セロテープ：HOPG、熱処理：SiC，CVD）	
（単層、複数層、平坦性、サイズ、・・・）	 エッジ構造制御、オーミック電極接合	
バンドギャップ制御、ドーピング	
物性値制御（高移動度、高安定性	
保護膜、・・・・	
高スピン拡散、・・・・）	

ミクロな評価・高精度計測・デバイス設計理論（従来デバイスとの整合性）	

Introduction

TTI SURFACE SCIENCE LAB.

Large Size Single Crystal Domain in CVD Graphene	
CVD Graphene: polycrystalline, randomly oriented 	Low nucleation density	èLarge domains	
Graphene on Pt	

High nucleation density	àSmall domains	

Graphene on Cu	

Toward wafer
scale
graphene
growth	1mm	L. Gao et al., NatureCommun. 3, 699 (2012).	

Z. Yan et al., ACS Nano 6, 9110
(2012).	

nucleation mechanism isimportant	Introduction

TTI SURFACE SCIENCE LAB.

In This Talk	u High pressure annealing of Cu before atmospheric

CVD 	à Suppress nucleation of graphene	u Discuss the nucleation mechanism	Experimental

TTI SURFACE SCIENCE LAB.

High Pressure Annealing and Atmospheric CVD	pressure gauge

Cu foil (100 µm ,Nilaco)quartz tube

inner quartz tube
Needlevalve

tubularfurnace
RotaryPump
CH4/Ar Ar

High pressure
annealing	～0.34 MPa, 1050 ﾟC	
H2/Ar, 5 h	H2ballvalve

exhaustAtmospheric
CVD growth	ATM, 1050 ﾟC	H2/Ar/CH4(10 ppm)	

Observation	Ø SEM, AFM,Auger mapping	Results and discussion

TTI SURFACE SCIENCE LAB.

SEM Observation of Graphene on Cu	
Atmospheric Pressure Annealing
10 min20 min30 min100 µmHigh Pressure Annealing
10 min20 min30 min

Low nucleation density on high pressure (HP) annealed Cu	

Results and Discussion	TTI SURFACE SCIENCE LAB.

AFM: #240 Graphene/Cu <Threefold Annealing>	

20 um	

-20 um	Results and discussion

TTI SURFACE SCIENCE LAB.

2Nucleation density (1/mm )High Pressure Annealing Reduced the Nucleation	

1500
ATMHigh pressure

100050000102030Time (min)3 times lower nucleation density on HP Cu	

Results and discussion

TTI SURFACE SCIENCE LAB.

AFM Images of the Pretreated Cu Before Growth	ATM	

1.7nm

High pressure	

5.0nm~100 nm

200 nm

200 nm-1.7nmThe step terrace structure after the HP annealing
indicates clean and smooth surface	à High pressure suppressed evaporation of Cu	

-5.0nmResults and discussion

TTI SURFACE SCIENCE LAB.

Impurity Particles on Cu	
ATM	Impurity Particles	

1.5nm

High pressure	

2 µm

500 nm-1.5nmSampleATMHPDensity	  of	  particles

7.0nm-7.0nmSurface
StructureDensity	  of	  graphene(1/μm )Height(nm)

0.86
0.10

5.2±0.653±5-­‐Step	  terrace

7.5x1022.5x10222(1/μm )Results and discussion

TTI SURFACE SCIENCE LAB.

Auger Mapping of the Impurity Particles	
Sample: 10 min CVD growth on ATM annealed Cu	

SEM

10 µmC	  KLL

Si	  KLLL S

Hexagonal graphenesØ The particle contains Si	Ø Large (L) particle was located on the center of graphene	Ø Many small (S) particles were on Cu substrate	

The impurity particles would be from the quartz tube	

Results and discussion

TTI SURFACE SCIENCE LAB.

Particle-Assisted Nucleation	
QuartzQuartzDeposition

H2/Ar	  Desorption

H2/Ar	  Diffusion

Cu

Cu

QuartzQuartzQuartzQuartzAggregation

Nucleation	  and	  GrowthSiOx

H2/Ar	  H2/Ar/CH4	  CuCuQuartzQuartzResults and discussion

TTI SURFACE SCIENCE LAB.

Electropolishing of Cu before annealing	
Electropolishing + HP	

25.8nm

Sub-millimeter sized graphene	

~ 0.5 mm
5 µm

-24.8
nm

Terrace	  width:	  ～400	  nm	  Density	  of	  par@cles:	  ～0.01	  µm-­‐2	  u Electropolishing provided large terrace and low density of impurity	u Sub-millimeter graphene was grown through electropolishing and HP	

Conclusion

TTI SURFACE SCIENCE LAB.

Conclusion	u Effect of high pressure annealing of Cu on atmospheric CVD

graphene growth was studied	u Role of high pressure annealing is suppression of evaporationof Cu à step terrace surface formation 	u Auger imaging revealed that the Si containing particle waslocated on the center of graphene	
u Particle-assisted nucleation process is suggested	u Combining electropolishing and high pressure annealing,
submillimeter sized graphene growth was succeeded	

Thank you for listening