Catalyst engineering for growth of one dimensional nanostructures

Catalyst Engineering for Growth of One-Dimensional Nanostructures YUN JIA (B. ENG. BEIJING UNIV. OF POSTS AND TELECOM.) (M.S. NATIONAL UNIVERSITY OF SINGAPORE) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILIOSOPHY IN ADVANCED MATERIALS FOR MICRO‐ AND NANOSYSTEMS (AMM&NS) SINGAPORE‐MIT ALLIANCE NATIONAL UNIVERSITY OF SINGAPORE 2010 Acknowledgements This project would not have been feasible without the guidance, support and constant encouragement of many individuals. Firstly, I would like to express my deepest gratitude to my thesis supervisors, Professor Choi Wee Kiong, Professor Carl V. Thompson and Associate Professor Hong Minghui for their invaluable guidance and instruction during the progress of my research. In addition, I would also like to thank Professor Henry I. Smith, Prof. John Thong, Mr. Koo Chee Keong and Dr. Foo Yong Lim, who provided me with their invaluable advices, suggestions and help. As most of the research work was conducted in the Microelectronics Laboratory, Laser Microprocessing Laboratory and CICFAR at NUS, I would like to extend my greatest gratitude to Mr. Walter Lim, Ms. Xiao Yun, Ms. Koh Hwee Lin and Mrs. Ho Chiow Mooi for all the kindest assistance rendered during the course of my research. i During my stay in SMA, I had many insightful discussions with my fellow schoolmates Roy, Hong Peng, Zheng Fei, Xiaodong, Tze Haw, Khalid, Raja, Wei Beng, Zhu Mei, Bihan, Yudi, Ria, Trong Thi, Zongbin, Tang Min, Caihong, Chin Seong, Zaichun, Zhi Qiang, Kay Siang, Hong Hai, Lin Ying, Boon Chong, Doris, Zhou Yi and Zi Yue. I would like to thank them for their great companionship. Last but not the least, this thesis is especially dedicated to my wife Huijuan and both of our parents who have been supporting me throughout my studies. Their indefinite love has made all the difference. ii Table of Contents Acknowledgements . Table of Contents . iii Summary vi List of Figures viii Chapter Introduction . 1.1 Background 1.2 Motivation 1.3 Organization of Thesis . Chapter Literature Review 2.1 Introduction 2.2 Bottom-up synthesis of ordered metal particle as catalyst on silicon 2.3 Synthesis of ordered vertically-aligned carbon nanotubes (CNTs) and carbon nanofibers (CNFs) 16 2.4 Field emission studies of ordered vertically-aligned carbon nanotubes and carbon nanofibers 27 Chapter Experimental Techniques 32 3.1 Introduction 32 3.2 Wafer Cleaning 33 3.3 Thermal Oxidation and Annealing . 35 iii 3.4 Photoresist coating . 39 3.5 Lloyd‘s Mirror interference lithography 41 3.6 Etching of Silicon Oxide 44 3.7 Anisotropic etching of Silicon . 47 3.8 Metal film deposition by Evaporation . 48 3.9 Lift-off 52 3.10 Measurements of film thickness 53 3.11 Scanning Electron Microscopy 58 Chapter Synthesis of precisely located Au nanoparticle array on silicon surface and the growth of silicon nanowires . 61 4.1 Introduction 61 4.2 Agglomeration of thin Au film on flat silicon surface . 63 4.3 Placement of Au nanoparticles in inverted pyramid arrays . 72 4.4 Growth of silicon nanowires catalyzed by the precisely located Au nanoparticles array . 91 4.5 Summary 96 Chapter Synthesis of Vertically Aligned Carbon Nanofibers and Carbon Nanoneedles Array 99 5.1 Introduction 99 5.2 Placement of Ni nanopyramids in inverted pyramid arrays . 102 5.3 Synthesis of Carbon nanofiber and nanoneedle array 111 5.4 The mechanism of CNN formation 118 5.5 The formation of carbon nano-walrus structure . 128 iv 5.6 Summary 130 Chapter Field Emission Studies of Vertically Aligned Carbon Nanoneedles (VACNNs) Array 131 6.1 Introduction 131 6.2 Geometrical tuning of Carbon Nanoneedles array . 134 6.3 Summary 147 Chapter Conclusions and future works . 148 7.1 Future works 151 Reference . 155 Publications . 169 Journals: . 169 Conferences: 169 v Summary The objective of this study is to engineer catalysts for the vapor-liquidsolid (VLS) and Vapor-Solid-Solid (VSS) growth of one-dimensional nanostructures. Firstly, this study focuses on the large-area synthesis of Au nanoparticles with tunable size and distribution. A combined top-down (interference lithography) and bottom-up approach (agglomeration of thin Au film) was developed to enable the precise placement of Au nanoparticles into inverted pyramids on silicon surface. The size of the nanoparticles can be tuned effectively by varying the deposited Au layer thickness and the annealing temperature. For the sample annealed at 1000°C, the size of the nanoparticles was found to be smaller than those annealed at a lower temperature of 600°C. This was found to be predominantly due to desorption of Au atoms. The Au nanoparticles were used as catalysts for the growth of silicon nanowires via the Vapor-Liquid-Solid (VLS) mechanism. The nanowires are of vi uniform diameter, with one wire grown from each pit. The nanowires, however, are randomly oriented as a thin layer of native oxide exists between the Au particle and the pyramid wall. The patterning technique was further modified to precisely place Nickel nanopyramids into inverted pyramid array. Plasma enhanced chemical vapor deposition (PECVD) technique was used for the growth of carbon nanofibers (CNFs) and carbon nanoneedles (CNNs). The effects of plasma power, temperature and gas ambient were examined on the formation of CNFs and CNNs. Finally, the field emission characteristics of the large area vertically aligned CNNS with pre-determined needle‘s diameter, spacing, length and tip sharpness were examined. We found that the optimum condition occurred when the interfiber-distance-to-fiber-height-ratio was equal to 1. This was consistent with other experimental data in the literature, but at variance with theoretical predictions. Possible reasons were proposed for this discrepancy between theory and our experimental results. vii List of Figures Figure 2-1: Schematic drawing of the VLS mechanism: (A) diffusion of silicon species from the vapor source, (B) incorporation, (C) diffusion through the liquid droplet, and (D) crystallization [3] [4]. . 11 Figure 2-2: Representative micrographs of the four major categories of dewetting on topography that were observed. (A) Multiple particles formed per pit with no ordering, 377 nm period substrate topography with 16nm thick film. (B) Ordered arrays of one particle per pit with no extraneous particles, 175 nm period narrowmesa substrate with 21 nm thick film. (C) Film not interacting with topography, 175 nm period wide-mesa substrate with 21 nm thick film. (D) Ordered arrays of one particle per pit with particles on mesas, 175 nm period wide-mesa substrate with 16 nm thick film [6]. . 13 Figure 2-3: SEM images showing the appearance of dewetted Co films on patterned substrates on annealing at a) 600 and b–e) 850 ºC. The samples shown in (a), (b), (d) and (e) were made by using template C (pit-to-mesa ratio ≈5.7) and the sample in (c) was made with template A (≈2.5). Co thickness: a–c) 15, d) 8, and e) nm. [8] . 14 Figure 2-4: Schematic demonstration of CNT (A) root growth mechanism and (B) tip growth mechanism. 17 Figure 2-5: Image sequence of a growing carbon nanofiber. Images a–h illustrates the elongation/contraction process. Drawings are included to guide the eye in locating the positions of mono-atomic Ni step edges at the C-Ni interface. The images are acquired in situ with CH4:H2 = 1:1 at a total pressure of 2.1 mbar with viii the sample heated to 536.8 ºC. All images are obtained with a rate of frames per seconds. Scale bar nm. [12] . 19 Figure 2-6: Schematic structure of carbon nanotubes and carbon nanofibers. (A) Nanotube and (B) Stacked cone nanofibers. . 20 Figure 2-7: SEM images of (A) SWCNT, (B) MWCNT and (C) CNF; TEM images of (D) SWCNT, (E) MWCNT and (F) CNF. . 21 Figure 2-8: SEM images of ordered vertically-aligned carbon nanotubes and carbon nanofibers array synthesized by (A) (B) E-beam lithography, (C) nanosphere lithography (D) nanoimprinting lithography (E) Anodized Aluminum Oxide template and (F) photolithography. 23 Figure 2-9: Carbon nanocone growth on a Ni catalyst particle. (A) Nickel film agglomerates into different size islands; (B) catalyzed growth stage; carbon adatoms diffuse through Ni catalyst particle; and (C) direct growth stage; carbon adatoms diffuse about the nanocone‘s surface. [24] . 25 Figure 2-10: Simulated nanocone arrays. (A) The primary nanocone arrays on an islanded catalyst film; (B) the primary nanocone array and secondary selfassembled nanocones between the primary nanocones; and (C) the final equalized pattern. Insets show the corresponding experimental patterns [24]. . 26 Figure 2-11: Schematic demonstration of (A) F-N tunneling and (B) CNT filed emission test setup. . 28 Figure 2-12: SEM images of: (A) CNTs film [31] and (B) random VACNTs array [32]. . 29 ix References References [1] Feynman, Richard P., Engineering and Science, vol. XXIII, no. 5, February 1960. [2] Yan, X., Liu, D., Ci, L., Wang, J., Zhou, Z., Yuan, H., Song, L., Gao, Y., Liu, L., Zhou, W., Wang, G., Xie, S., J. Cryst. Growth, 2003, vol. 257, p. 69. [3] Canham, L., Appl. Phys. Lett., 1990, vol. 57, p. 1046. [4] Katz, D., Wizansky, T., Milo, O., Phys. Rev. Lett., 2002, vol. 89, p. 86801. [5] Duan, X., Wand, J., Lieber, C., Appl. Phys. Lett., 2000, vol. 76, p. 1116. [6] Ma, D., Lee, C., Au, C., Tong, S., Lee, S., Science, 2003, vol, 299, p.1874. [7] Duan, X., Huang, Y., Cui, Y., Wang, J., Lieber, C., Nature, 2001, vol. 409, p. 66. [8] Cui, Y., Zhong, Z., Wang, D., Wang, W., Lieber, C., Nano Lett., 2003, vol. 3, p.149. [9] Cui, Y., Lieber, C., Science, 2001, vol. 291, p. 851. [10] Hahm, J., Lieber, C., Nano Lett., 2004, vol. 4, p. 51. ~ 155 ~ References [11] Cui, Y., Wei, Q., Park, H., Lieber, C., Science, 2001, vol. 293, p. 1289. [12] Iijima, S., Ichihashi, T., Nature, vol. 363, p. 603. [13] Fan S., Chapline M.G., Franklin N.M., Tombler T.W., Cassell A.M., Dai H., Science, 1999, vol. 283, p. 512. [14] Treacy M.M.J., Ebbesen T.W., Gibson J.M., Nature (London), 1996, vol. 381, p. 687. [15] Nilsson, L., Groening, O., Emmenegger, C., Kuettel, O., Schaller, E., Schlapbach, L., Appl. Phys. Lett., 2000, vol. 76, p. 2071. [16] Arsenault, A. C., Nat. Mater., 2006, vol. 5, p. 179. [17] Tan, T. L., Wong, D., and Lee, R., Opt. Express, 2004, vol.12, p. 4847. [18] Jewell, S. A., Vukusic, P., and Poberts, N. W., New J. Phys., 2007, vol.9, p. 99. [19] Huang, J. Y., Wang, X. D., Wang, Z. L., Nano Lett., 2006, vol. 6, p. 2325. [20] Fujii, S., Ryan, A. J., Armes, S. P., J. Am. Chem. Soc., 2006, vol. 128, p. 7882. [21] Geissler, M., Xia, Y. N., Adv. Mater., 2004, vol. 16, p. 1249. [22] R.S. Wagner, W.C. Ellis, Appl. Phys. Lett. 1964, vol. 4, p. 89. ~ 156 ~ References [23] Hu, J.T., Odom, T.W., and Lieber, C.M., Acc. Chem. Res., 1999, Vol 32, p 435. [24] Wagner, R. S., and Ellis, W. C., Appl. Phys. Lett., 1964, vol. 4, p. 89. [25] Yang, P. D., Dalton Transactions, 2008, vol. 33, p. 4387. [26] Schmidt,V., Senz, S., and Gösele,U., Phys. Rev. B, 2007, vol. 75, p. 045335. [27] Westwater, J., Gosain, D. P., Tomiya, S., Usui, S., and Ruda, H., J. Vac. Science and Tech. B, 1997, vol. 15, p. 554. [28] Giermann, A. L., Thompson, C. V., and Smith, H. I., Material Research Society Symposium Proceeding 2004, vol. 818, M3.3. [29] A Giermann, A. L., Thompson, C. V., Appl. Phys. Letts., 2005, vol. 86, p. 121903. [30] Oh, Y., Ross, C. A., Jung, Y. S., Wang, Y., and Thompson, C. V., Small, 2009, vol. 5, p. 860. [31] Iijima, S., Ichihashi, T., Nature, vol. 363, p. 603. [32] Iwasaki, T., Zhong, G.F., Aikawa, T., Yoshida, T., Kawarada, H., J. Phys. Chem. B, 2005, vol. 109, p. 19556. ~ 157 ~ References [33] Yasuda, A., Kawase, N., Mizutani, W., J. Phys. Chem. B, 2002, vol. 106, p. 13294. [34] Helveg, S.; Lopez-Cartes, C.; Sehested, J.; Hansen, P.L.; Clausen, B. S.;, Rostrup-Nielsen, J. R.; Abild-Pedersen, F.; Nørskov. J. K. Nature, 2004, vol. 427, p. 426. [35] Meyyappan, M., J. Phys. D: Appl. Phys., 2009, vol. 42, p. 213001. [36] Nolan, D., Lynch, D. C., and Cutler, A. H., J. Phys. Chem. B, 1998,vol. 102, p. 4165. [37] Teo, K.B.K., Chhowalla, M., Amaratunga, G.A.J., Milne, W.I., Pirio, G., Legagneux, P., et al. Appl. Phys. Letts., 2002, vol. 80, p. 2011. [38] Merkulov, V. I., Lowndes, D. H., Wei, Y. Y., Eres, G., Appl. Phys. Lett., 2000, vol. 76, 3555. [39] Park, K.H., Lee, S., Koh, K.H., Lacerda, R., Teo, K.B.K., Milne, W.I. J., J. Appl. Phys., 2005, vol. 97, p. 024311. [40] Vieria, S.M.C., Teo, K.B.K., Milne, W.I., Groning, O., Gangloff, L., Minoux, E., Legagneux, P., Appl. Phys. Letts., 2006, vol. 89, p. 022111. [41] Suh, J.S., Jeong, K.S., Lee, J.S., Han, I., Appl. Phys. Letts., 2002, vol. 80, p. 2392. ~ 158 ~ References [42] Yoon, S.M., Chae, J., Suh, J.S., Appl. Phys. Letts., 2004, vol. 84, p. 825. [43] Tsakadze, Z.L., Ostrikov, K., Long, J.D., Xu, S., Diam. Relat. Mater., 2004, vol. 13, p. 1923. [44] Ostrikov. K., Long, J.D., Rutkevych ,P.P., Xu, S., Vacuum, 2006, vol. 80, p. 1126. [45] Tsakadze, Z.L., Ostrikov, K., Xu, S., Surf. Coat. Technol., 2005, vol. 191 p. 49 [46] Tsakadze, Z.L., Levchenko, I., Ostrikov, K., Xu, S., Carbon, 2007, vol. 45, p. 2022. [47] Wang, W.H., Lin, Y.T., Kuo, C. T., Diam. Relat. Mater., 2005, vol. 14, p. 907. [48] Ren, Z. F., et al., Appl. Phys. Lett., 1999, vol. 75, p. 1086. [49] Fowler, R.H., Nordheim, L.W., Proc. R. Soc. (London), 1928, vol. A119, p.173. [50] Nordheim, L.W., Proc. R. Soc. (London), 1928, vol. A121, p. 626. [51] Nordheim, L.W., Z. Physik, 1929, vol. 30, p.177. [52] Heer, W. A., Châtelain, A., Ugarte, D., Science, 1995: vol. 270, p. 1179. ~ 159 ~ References [53] Bonard, J.M., Salvetat, J. P., Stockli, T., Heer, W. A., Forro, L., Chatelain, A., Appl. Phys. Lett., 1998, vol. 73, p. 918. [54] Chhowalla, M., Ducati, C., Rupesinghe, N. L., Teo, K. B. K., Amaratunga, G. A. J., Appl. Phys., 2001, vol. 79, p. 2079. [55] Nilsson, L., Groening, O., Emmenegger, C., Kuettel, O., Schaller, E., Schlapbach, L., et al., Appl. Phys. Lett., 2000, vol. 76, p. 2071. [56] Smith, R.C., Silva, S.R.P., Appl. Phys. Lett., 2009, vol. 94, p. 133104. [57] Plummer, J.D., Deal, M.D. Griffin, P.B., Silicon VLSI Technology, Fundamentals, Practice and Modeling, 2000, Prentice Hall. [58] Walsh, M., Ph.D. thesis, MIT, Sept. 2004, "On the design of lithographic interferometers and their applications." [59] Huang, Z. P., Fang, H., Zhu, J., Adv. Mat., 2007, vol. 19, p. 744. [60] Vu, Q., Sfricker, D.A., Zavracky, P.M., J. Electrochemical Society, 1996, vol. 143, p. 1372. [61] Binnig, G., Quate, C.F., Gerber, C., Phys. Rev. Lett., 1986, vol. 56, p. 930. [62] Ohnesorge, F., Binnig, G., Science, 1993, vol. 260, p. 1451. [63] Cowburn, R.P., Adeyeye, A.O., Bland, J.A.C., Appl. Phys. Lett., 1997, vol. 70, p. 2309. ~ 160 ~ References [64] Maier, S.A., Brongersma, M.L., Kik, P.G., Meltzer, S., Requicha, A.A.G., Atwater, H.A., Adv. Mater., 2001, vol. 13, p. 1501. [65] Wu, Y., Cui, Y., Huynh, L., Barrelet, C.J., Bell, D.C., Lieber, C.M., Nano Lett., 2004, vol. 4, p. 433. [66] Hochbaum, A.I., Fan, R., He, R., Yang, P., Nano Lett., 2005, vol. 5, p. 457. [67] Cui, Y., Lauhon, L.J., Gudiksen, M.S., Wang, J., Lieber, C.M., Appl. Phys. Lett., 2001, vol. 78, p. 2214. [68] Zhong, Z., Qian, F., Wang, D., Lieber, C.M., Nano. Lett., 2003, vol. 3, p. 343. [69] Cui, Y., Zhong, Z., Wang, D., Wang, W.U., Lieber, C.M., Nano. Lett., 2003, vol. 3, p. 149. [70] Wagner, R.S., Ellis, W.C., Appl. Phys. Lett., 1964, vol. 4, p. 89. [71] Huang, M.H., Wu, Y., Feick, H., Tran, N., Weber, E., Yang, P., Adv. Mater., 2001, vol. 13, p. 113. [72] Hu, W., Sarveswaran, K., Lieberman, M., Bernstein, G.H., J. Vac. Sci. Technol. B, 2004, vol. 22, p. 1711. [73] He, J.H., Hsu, J.H., Wang, C.W., Lin, H.N., Chen, L.J., Wang, Z.L., J. Phys. Chem. B, 2006, vol. 110, p. 50. ~ 161 ~ References [74] Kwon, J.Y., Yoon, T.S., Kim, K.B., Min, S.H., J. Appl. Phys., 2003, vol. 93, p. 3270. [75] Jiran, E., and Thompson, C.V., Thin Solid Films, 1992, vol. 208, p. 23. [76] Gadkari, P.R., Warren, A.P., Todi, R.M., Petrova, R.V., Coffey, K.R., J. Vac. Sci. Technol. A, 2005, vol. 23, p. 1152. [77] Jiran, E., Thompson, C.V., J. Electron. Mater., 1990, vol. 19, p. 1153. [78] Palik, E.D., Bermudez, V.M., Glembocki, O.J., J. Electrochemical Society, 1985, vol. 132, p. 871. [79] Vu, Q., Sfricker, D.A., Zavracky, P.M., J. Electrochemical Society, 1996, vol. 143, p. 1372. [80] Giermann, A.L., Thompson, C.V., Appl. Phys. Lett., 2005, vol. 86, p. 121903. [81] Smith, D.L., McGraw-Hill, N.Y., 1995, p. 588. [82] Ohring, M., Academic Press, London, 1992, p. 81. [83] Liu, Z.Q., Zhou, W.Y., Sun, L.F., Tang, D.S., Zou, X.P., Li, Y.B., Wang, C.Y., Wang, G., Xie, S.S., Appl. Phys. Lett., 1997, vol. 70, p. 2309. ~ 162 ~ References [84] Chhowalla, M., Teo, K.B.K., Ducati, C., Rupesinghe, N.L., Amaratunga, G.A.J., Ferrari, A.C., Roy, D., Robertson, J., Milne, W.I., J. Appl. Phys., 2001, vol. 90, p. 5308. [85] Yoon, Y.J., Bae, J.C., Baik, H.K., Cho, S.J., Lee, S.J., Song, K.M., Myung, N.S., Physica B, 2002, vol. 323, p. 318. [86] Xing, Y.J., Yu, D.P., Xi, Z.H., Xue, Z.Q., Chin. Phys., 2002, vol. 11, p. 1047. [87] Fan, S., Chapline, M. G., Franklin, N. M., Tombler, T.W., Cassell, A.M., Dai. H., Science, 1999, vol. 283, p. 512. [88] Xu, Y., Zhang, Y., Suhir, E., Wang. X.W., J. Appl. Phys., 2006, vol. 100, p. 074302. [89] Treacy, M. M. J., Ebbesen, T. W., Gibson, J. M., Nature, 1996, vol. 381, p. 678. [90] Chhowalla, M., Teo, K. B. K., Ducati, C., Rupesinghe, N. L., Amaratunga, G. A., Ferrari, A. C., Roy, D., Robertson, J., Milne. W. I. J., J. Appl. Phys., 2001, vol. 90, p. 5308. ~ 163 ~ References [91] Melechko, A.V., Merkulov, V.I., McKnight, T.E., Guillorn, M.A., Klein, K.L., Lowndes, D.H., Simpson, M.L., J. Appl. Phys., 2005, vol. 97, p. 041301. [92] Teo, K. B. K., Chhowalla, M., Amaratunga, G. A., Milne, W. I., Pirio, G., Legagneux, P., Wyczisk, F., Pribat, D., Hasko, D. G., Appl. Phys. Letts., 2002, vol. 80, p. 2011. [93] Park, K. H., Lee, S., Koh, K. H., Lacerda, R., Teo, K. B. K., Milne, W. I. J., J. Appl. Phys., 2005, vol. 97, p. 024311. [94] Vieria, S. M. C., Teo, K. B. K., Milne, W. I., Groning, O., Gangloff, L., Minoux, E., Legagneux, P., Appl. Phys. Letts., 2006, vol. 89, p. 022111. [95] Suh, J. S., Jeong, K. S., Lee, J. S., Han, I., Appl. Phys. Letts., 2002, vol. 80, p. 2392. [96] Yoon, S. M., Chae, J., Suh, J. S., Appl. Phys. Letts., 2004, vol. 84, p. 825. [97] Choi, W.K., Liew, T.H., Dawood, M.K., Smith, H.I., Thompson, C.V., Hong, M.H., Nano Lett., 2008, vol. 8, p. 3799. [98] Dawood, M.K., Liew, T.H., Lianto, P., Hong, M.H., Tripathy, S., Thong, J.T.L., Choi, W.K., Nanotechnology, 2010, vol. 21, p. 205305. ~ 164 ~ References [99] Vourdas, N., Kontziampasis, D., Kokoris, G., Constantodis, V., Goodyear, A., Tserepi, A., Cooke, M., Gogolides, E., Nanotechnology, 2010, vol. 21, p. 085302. [100] Tsakadze, Z.L., Levchenko, I., Ostrikov, K., Xu, S., Carbon, 2007, vol. 45, p. 2022. [101] Park, K.H., Lee, S., Koh, K.H., Lacerda, R., Teo, K.B.K., Milne, W.I.J., J Appl. Phys., 2005, vol. 97, p. 024311. [102] Henzie, J., Kwak, E.S., Odom, T.W., Nano Lett. 2005, vol 5, p. 1199 [103] Levchenko, I., Ostrikov, K., Long, J.D., Xu, S., Appl. Phys. Lett., 2007, vol. 91, p. 113115. [104] Denysenko, I., Ostrikov, K., Appl. Phys. Lett., 2007, vol. 90, p. 251501. [105] Helveg, S., Lopez-Cartes, C., Sehested, J., Hansen, P. L., Clausen, B. S., Rostrup-Nielsen, J. R., Abild-Pedersen, F., Nørskov. J. K., Nature, 2004, vol. 427, p. 426. [106] Ci, L., Xu, Z., Wang, L., Cao, W., Ding, F., Kelly, K. F., Yajobson, B. I., Ajayan, P. M., Nano. Res., 2008, vol. 1, p. 116. [107] Campos, L. C., Manfrinato, V. R., Sanchez-Yamagishi, J. D., Kong. J., Jarillo-Herrero, P., Nano. Lett., 2009, vol. 9, p. 2600. ~ 165 ~ References [108] Ci, L., Xu, Z., Wang, L., Cao, W., Ding, F., Kelly, K.F., Yajobson, B.I., Ajayan, P.M., Nano. Res., 2008, vol. 1, 116. [109] Fan, S., Chapline, M.G., Franklin, N.M., Tombler, T.W., Cassell, A.M., Dai, H., Science, 1999, vol. 283, p. 512. [110] Treacy, M.M.J., Ebbesen, T.W., Gibson, J.M., Nature (London) 1996, vol. 381, p. 678. [111] Chhowalla, M., Teo, K.B.K., Ducati, C., Rupesinghe, N.L., Amaratunga, G.A.J., Ferrari, A.C., J. Appl. Phys., 2001, vol. 90, p. 5308. [112] Teo, K.B.K., Chhowalla, M., Amaratunga, G.A.J., Milne, W.I., Pirio, G., Legagneux, P., Appl. Phys. Letts., 2002, vol. 80, p. 2011. [113] Park, K.H., Lee, S., Koh, K.H., Lacerda, R., Teo, K.B.K., Milne, W.I., J. J. Appl. Phys., 2005, vol. 97, p. 024311. [114] Vieria, S.M.C., Teo, K.B.K., Milne, W.I., Groning, O., Gangloff, L., Minoux, E., Legagneux, P., Appl. Phys. Letts., 2006, vol. 89, p. 022111 [115] Suh, J.S., Jeong, K.S., Lee, J.S., Han, I., Appl. Phys. Letts., 2002, vol. 80, p. 2392. [116] Yoon, S.M., Chae, J., Suh, J.S., Appl. Phys. Letts., 2004, vol. 84, p. 825. ~ 166 ~ References [117] Nilsson, L., Groening, O., Emmenegger, C., Kuettel, O., Schaller, E., Schlapbach, L., Appl. Phys. Letts., 2000, vol.76, p. 2071. [118] Smitha, R. C., Silva, S.R.P., Appl. Phys. Lett., 2009, vol. 94, p. 133104. [119] Xu, N., High Voltage Vacuum Insulation, R. V. Latham, ed., Academic Press Limited, London; 1995 [120] Rinzler, A.G., Hafner, J.H., Nikolaev, P., Lon, L., Kim, S.G., Tomanek, D., Science, 1995, vol. 269, p. 1550 [121] Tsai, S.H., Chao, C.W., Lee, C.L., Shih, H.C., Appl. Phys. Lett., 1999, vol. 74, p. 3462 [122] Cumings, J., Collins, P.G., Zettl, A., Nature, 2000, vol. 406, p. 586. [123] Merkulov, V.I., Guillorn, M.A., Lowndes, D.H., Simpson, M.L., Voelkl, E., Appl. Phys. Lett., 2001, vol. 79, p.1178. [124] Chen, J., Zhou, X., Deng, S.Z., Xu, N.S., Ultramicroscopy, 2003,95, p. 153 [125] Wei, B. Q., Vajtai, R., Ajayan, P. M., Appl. Phys. Lett., 2001, vol. 79, p. 1172. [126] Osman, M. A., and Srivastava, D., Nanotechnology, 2001, vol. 12, p. 21. ~ 167 ~ References [127] Hone, J., Whitney, M., Piskoti, C., and Zettl, A., Phys. Rev. B. 1999, vol. 59, p.2514 [128] Anantram, M. P., Datta, S., and Xue, Y., Phys. Rev. B, 2000, vol. 61, p. 14219. [129] Mingo, N., and Han, J., Phys. Rev. B, 2001, vol. 64, p. 201401. [130] Kreupl, F., Graham, A. P., Duesberg, G. S., Steinhogl, W., Liebau, M., Unger, E., Honlein, W., Microelectron. Eng., 2002, vol. 64, p. 399. [131] Li, J., Ye, Q., Cassell, A., Ng, H.T., Stevens, R., Han, J., Meyyappan, M., Appl. Phys. Lett., 2003, vol. 82, p.2491. [132] Barbara, T. D., Chen, H., Cassell, A.M., Andrews, R., Meyyappan, M., Li, J., Small, 2006, vol. 2, p. 89. [133] McKnight, T. E., Melechko, A. V., Hensley, D. K., Mann, D. G. J., Griffin, G. D., and Simpson, M. L. Nano Lett., 2004, vol. 4, p. 1213. [134] McKnight, T. E., Melechko, A. V., Griffin, G. D., Guillorn, M. A., Merkulov, V. I., Serna, F., Hensley, D. K., Doktycz, M. J., Lowndes, D. H., Simpson, M. L. Nanotechnology, 2003, vol. 14, p. 551. ~ 168 ~ Publications Publications Journals: • J. Yun, Rui Wang, M. H. Hong, J. T. L. Thong, Y. L. Foo, C. V. Thompson and W. K. Choi, ―Converting carbon nanofibers to carbon nanoneedles: catalyst splitting and reverse motion ‖ Nanoscale, 2010, 2, 21805. • J. Yun , Rui Wang, W. K. Choi, J. T. L. Thong, C. V. Thompson, Mei Zhu, Y.L. Foo, M.H. Hong, ―Field emission from a large area of vertically-aligned carbon nanofibers with nanoscale tips and controlled spatial geometry ‖ Carbon, 2009, 48, 5, 362. • W. K. Choi, T. H. Liew, H. G. Chew, F. Zheng, C. V. Thompson, Y. Wang, M. H. Hong, X. D. Wang, L. Li, J. Yun, ―A combined top-down and bottom-up approach for precise placement of metal nanoparticles on silicon‖, Small, 2008, 4, 330. Conferences: • J. Yun, R. Wang, MH Hong, YL Foo, JTL Thong, CV Thompson and WK Choi, ―First observation of Ni catalyst migration inside CNF‖ Materials Research Society Spring Meeting, AA 1.43, 2010 • J. Yun , Rui Wang, W. K. Choi, J. T. L. Thong, C. V. Thompson, Mei Zhu, Y.L. Foo, M.H. Hong,―Field emission studies of large area and well controlled geometry Vertically-Aligned Carbon NanoFibers with nanoscale tips‖, 6th International Symposium on Nanomanufacturing, 2010. ~ 169 ~ Publications • T. H. Liew, M. K. Dawood, O. S. Rajamouly, J. Yun, G. M. H. Lim, B. Li, W. K. Choi, H. I. Smith, C. V. Thompson, M. H. Hong, ―Fabrication of Large and Highly Ordered Arrays of One Dimensional Silicon Nanostructures‖, Materials Research Society Spring Meeting, AA 9.11, 2009. • J. Yun, T. H. Liew, M. Zhu, M. K. Dawood, O. S. Rajamouly, W. K. Choi, C. V. Thompson, M. H. Hong, ―Synthesis of Monodisperse Au Nanoparticles in Lithographically Defined Inverted Pyramids Array‖, Materials Research Society Spring Meeting, BB 6.18, 2009. • T. H. Liew, J. Yun, F. Zheng, H. G. Chew, W. K. Choi, Y. Wang, C. V. Thompson, M. H. Hong, ―Synthesis of Metal Nanoparticles with Precise Position Control via Laser Interference Lithography‖, 5th International Symposium on Nanomanufacturing, 2008. ~ 170 ~ [...]... 6 will examine the effects of plasma power, temperature and gas ambient on the formation of Carbon nanofibers and Carbon nanoneedles during the PECVD growth and plasma-enhanced etching Chapter 7 will provide a summary of the accomplishments of this project and provide recommendations for future work ~7~ Chapter 2 Chapter 2 Literature Review 2.1 Introduction One- dimensional nanostructures such as semiconducting... array of carbon nano-needles The diameter of each CNN at the base was ~200 nm; the length was ~1 µm (45ºTilt) The inset is a magnified view of a portion of the CNF array, with a scale bar of 500 nm 115 Figure 5-9: (A) TEM image of a CNN The scale bar is 100nm; (B) HRTEM image of the tip of the CNN The scale bar is 5nm (C) SEM image (45°tilt) of part of a CNN array with CNN base diameters of 100... location of the nanostructures, we will review in this chapter, firstly, the existing techniques in ~8~ Chapter 2 synthesis of silicon nanostructures with special emphasis on the methods to control the sizes and location The second part of this chapter will be concentrating on the synthesis of one- dimensional carbon nanostructures, the growth mechanism of carbon nanotubes and carbon nanofibers This will... preparation of the metal catalyst for the VLS growth of ~ 11 ~ Chapter 2 silicon nanowires is via the agglomeration of a thin metal film deposited on a flat substrate [27] Inevitably, the nanowires that are subsequently grown exhibit a very wide distribution of sizes and spacing, due to the poor control of the size and spacing of metallic nanoparticle catalysts associated with the dewetting method It is of. .. the head of the growing nanotube, labeled as tipgrowth mechanism [33] (Figure 2-4 B) ~ 16 ~ Chapter 2 Figure 2-4: Schematic demonstration of CNT (A) root growth mechanism and (B) tip growth mechanism Helveg et al carried out TEM experiments for the tip -growth mechanism, in which in-situ observations of CNF growth were made [34] They observed a liquid-like oscillation in the shape of the Ni catalysts... upper part of the CNF through which the bottom catalyst has passed (B) Magnified image of the body catalyst and (C) Magnified image of the top catalyst The scale bars are (A) 100nm, (B) 25nm and (C) 25nm 123 xiv Figure 5-12: Schematic diagram of the mechanism that is responsible for the Ni catalyst splitting and reverse motion observed in CNNs 124 Figure 5-13: SEM images of: (A) an... control of catalyst geometry and location, but are costly and produce small areas of device coverage (e.g EBL and IBL) Others provide relatively large areas of device coverage but suffer from restrictions on the catalyst geometry and location (e.g NSL, AAO) or the need for fairly complicated processes to change geometry parameters (e.g new masks for different spacings in the case of NIL) Hence, one of the... researchers all over the world However, the way in which nanotubes are formed is not exactly known The growth mechanism is still a subject of controversy, and more than one mechanism might be operative during the formation of CNTs For supported metals, such as nickel, cobalt or iron, carbon nanotube can form either by ―extrusion‖, also known as root -growth mechanism [32] (Figure 2-4 A), in which the nanotube... 37.5 mA) for 3 minutes, (C) full plasma power (plasma current fixed at 75 mA) for 3 minutes and (D) full plasma power for 5 minutes Scale bar 100 nm 127 Figure 5-14: SEM images of: (A) as-grown CNNs and (B) the same CNNs subjected to a second growth which causes branching to form a second tube The second growth was carried out at 700 ° at a pressure of 7.5 mbar in a 5:1 C mixture of NH3... method and then used to grow carbon nanofibers via Plasma-Enhanced-Chemical-Vapor-Deposition (PECVD) 1.3 Organization of Thesis This thesis is organized into seven chapters, with the first chapter being the introduction Chapter 2 will cover the theoretical background and literature review on the methods used for the preparation of metal catalysts for the VLS growth of silicon nanowires and carbon nanotubes . Catalyst Engineering for Growth of One-Dimensional Nanostructures YUN JIA (B. ENG. BEIJING UNIV. OF POSTS AND TELECOM.) (M.S. NATIONAL UNIVERSITY OF SINGAPORE) A THESIS SUBMITTED FOR. vi Summary The objective of this study is to engineer catalysts for the vapor-liquid- solid (VLS) and Vapor-Solid-Solid (VSS) growth of one-dimensional nanostructures. Firstly, this. desorption of Au atoms. The Au nanoparticles were used as catalysts for the growth of silicon nanowires via the Vapor-Liquid-Solid (VLS) mechanism. The nanowires are of vii uniform diameter,