Investigation on the growth of CNTs from SiO x and Fe 2 O 3 nanoparticles by in situ TEM

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1 The 5 th Workshop on Nucleation and Growth Mechanisms of SWCNTs Investigation on the growth of CNTs from SiO x and Fe 2 O 3 nanoparticles by in situ TEM Chang Liu Shenyang National Laboratory for Materials Science Institute of Metal Research, Chinese Academy of Sciences 72 Wenhua Road, Shenyang , China Flying L Guest Ranch,

2 Contents Background Method Results Conclusions and Indications

3 Traditional catalysts for the synthesis of SWCNTs Arc-discharge Fe or Co Laser ablation Ni+Co FCCVD Fe Iijima, S. Nature, 363 (1993) 603 Bethune, D.S. Nature, 1993,363,605 Thess, A. Science, 273 (1996) 483 Cheng, H.M. APL, 72 (1998) 3282 Nikolaev, P. CPL, 313 (1999) 91

4 Efficient growth of SWNTs Y. T. Zhu et al. Nature Mater Fe Result from Prof. F Wei S. Iijima et al. Science 2004 Fe, Al/Fe, Al 2 O 3 /Fe, Al 2 O 3 /Co Cheng et al. ACS Nano 2009 Fe

5 Challenges remained Selective growth of semiconducting/metallic or even specific chirality SWNTs Mechanism for the controlled growth

6 Theoretical predictions on the effect of catalyst on CNT structures Yazyev, O. V. PRL 2008,100, Ding, F. Nano Lett. 2008,8,463

7 Novel catalysts for the growth of SWNTs Takagi, D. Nano Lett. 2006,6,2642 Takagi, D. Nano Lett. 2008,8,832 Yuan, D.N. Nano Lett. 2008,8,2576 Zhou, W. W. Nano Lett. 2006,6,2987 Bhaviripudi, S. JACS 2007,129,1516

8 Novel catalysts for the growth of SWNTs J Zhang et al. Nano Lett, 2009 D Takagi et al. JACS, 2009

9 Non-metal catalyst (SiO x ) Scratching growth Sputtering growth Liu, B.L., Ren, W.C., Liu, C., Cheng, H. M. et al., JACS, 2009, 131, 2082

10 Why non-metal catalyst? Metal-free samples Deeper understanding of the growth mechanism of CNTs Control on the structure of CNTs Length sorted growth of SWNTs

11 Direct length-sorted growth of short SWNTs 20 S 40 S 60 S Finite length effect Electronic & electrical transport properties Optical properties; Thermal conductivity Carrier recombination Potential applications Scanning tips; Catalysts supports Biology imaging & molecular sensors BL Liu, WC Ren, C Liu, HM Cheng et al. ACS Nano 2009, 3: 3421

12 Why non-metal catalyst? Metal-free samples Deeper understanding of the growth mechanism of CNTs Still unclear and very important! Control on the structure of CNTs Length sorted growth of SWNTs

13 How does SiO x catalyst function? 3C + SiO 2 SiO + 2CO SiC + CO 2C + SiO A. Bachmatiuk et al. ACS Nano 2009

14 Direct observation in situ Under TEM High temperature Carbon source Catalyst particles

15 Environmental TEM Ni Vapor-liquid-solid growth mechanism Fe S. Helveg et al., Nature 427, 426 (2004). R. Sharma, Z. Iqbal, Appl. Phys. Lett. 84, 990 (2004). M. Lin et al., Nano Lett. 6, 449 (2006). S. Hofmann et al., Nano Lett. 7, 602 (2007). H. Yoshida, et al., Nano Lett. 8, 2082 (2008).

16 E beam atom injection Direct covalent bonding at interface Nucleation Interface J. A. Rodriguez-Manzo et al., Nat. Nanotechnol. 2, 307 (2007). J. A. Rodriguez-Manzo et al., Small 5, 2710 (2009).

17 Contents Background Our method Results Conclusions and Indications

18 Approach we developed CNT Nanofurnace Catalyst loading Carbon injection CNT growth

19 CNTs by AAO template method nanochannel C 2 H 2 CVD AAO AAO+C

20 Catalyst selected and loading SiO x Fe 2 O Chem Comm 2004, Chem Mater 2006, 18: 4109 JPCB 2004, 108: 8091 J Solid state Comm 2009 CVD of SiH 4 Liquid immersion in Fe(NO 3 ) 3 solution

21 Heating of the nanofurnace STM-TEM Holder (Nanofactory) TEM (Tecnai F20)

22 Contents Background Our method Results Conclusions and Indications

23 Iron oxide-filled CNTs Fe 2 O 3 : Crystallized 5-10nm

24 Structure characterization of the catalyst Fe2O3 36 A Fe3C

25 Snap shots of the CNT nucleation and growth process catalyzed by the Fe 2 O 3 catalyst

26 HRTEM of the catalyst during and after CNT growth Fe3C CNT growth Fe

27 Although graphitic layers surrounded Fe NPs are left after CNT growth, the active catalytic phase is Fe 3 C. During the CNT growth process, the catalyst NP is in a semi-liquid state.

28 SiO x -filled CNTs By CVD of SiH 4 Particle size 5-10 nm

29 Lift up of carbon layer from a big NP Surface diffusion Carbon layer lift-up

30 Formation of a carbon cap V=1.8 V I= 12 A

31 Formation of a SWNT BL Liu, DM Tang, C Liu, WC Ren, HM Cheng et al. JACS 2011, 133: 197.

32 No carbon precipitation observed over Si/SiC Si formed ~200 A SiC formed ~400 A

33 CVD growth of SWNTs from SiO 2 (upper) and Si (lower) particles

34 Optimized geometries and calculated adsorption energies of CHx over Si (111) and oxygen-modified Si

35 Growth of CNT from SiOx catalyst Surface-diffusion dominated catalysis process NP size (<5 nm) Composition (Provide a desired interaction with carbon layers) Cap forms preferentially at protrusions or interface Fragments connection Cap forms due to the inhomogeneity

36 Indications SiO x particle Solid state Amorphous Nucleation sites Protrusions Interface Growth Process Adsorption-Surface diffusion-lifting up Fe 3 C particle Semi-liquid Crystalline Nucleation sites Steps Edges Growth process Dissolved-Carbide- Precipitation

37 Growth models for the Fe 2 O 3 and SiO x NPs

38 Summary An in situ TEM method that can be used for investigating the growth mechanism of CNTs from various catalysts is developed. The growth of CNTs from SiO x and Fe 2 O 3 NPs were investigated comparatively. Distinct growth processes were observed, the SiO x catalyst keeps its solid state during the growth process, and the active catalyzing phase is amorphous SiO x rather than SiC. VSS and VLS growth mechanisms were proposed for the SiOx and Fe 2 O 3 catalyst, respectively.

39 Why non-metal catalyst? Understanding the growth mechanism Optimize the catalyst and growth conditions Realize a controlled growth Length sorted growth of SWNTs Transport characteristic and chirality control?

40 Growth of CNT from carbon fiber Carbon microcoil Sp2 Randomly

41 Current density: 10 4 A/cm 2 Passing by a high current

42 Formation of fullerenes and CNTs Induced by Joule heating and Electro immigration effect Tang, Liu, Cheng et al. Carbon 2009

43 Acknowledgements Mr. Bi-Lu Liu Dr. Dai-Ming Tang, Peng-Xiang Hou Prof. Hui-Ming Cheng, Wen-Cai Ren NSFC, MOST, and CAS

44 Thank you very much for your attention!