报告人：Yeshayahu Lifshitz 教授
Dept. of Materials Engineering, Technion, Haifa 32000, Israel
题目: Nanostructuring Carbon by Energetic Species: from Amorphous Carbon through Carbon Nanotubes to Diamond
地点：909号楼一楼B会议室(Conference Room B, 909-1F)
Energetic species in different forms play a major role in current thin film technology. The evolution of such films via energetic particle bombardment is a shallow implantation (“subplantation”) process1-3. The stopping of the energetic species in the bombarded target advances through three stages: (i) collisional stage in which the species are stopped by the target via atomic displacements, ionization and phonon excitations, (ii) the thermal relaxation stage in which the excess energy is dissipated in the target, (iii) the long term relaxation stage in which long term processes (diffusion, chemical reactions) take place. The final evolution of the structure is determined by the equilibrium between subsurface trapping at the final site and detrapping processes. Carbon is an excellent model system to study the structuring of materials by energetic species due to the host of possible configurations it forms. By properly altering the energy and temperature it is possible to form: (i) amorphous carbon films with a local configuration and properties ranging between those of graphite (sp2 hybridization) and diamond (sp3), (ii) ordered graphitic films including carbon multiwall tubes4, (iii) nanocrystalline diamond5-7, (iv) porous carbon. The processes leading to the different carbon structures will be highlighted through experimental data and molecular dynamic simulations.
1 Y. Lifshitz, S.R. Kasi and J.W. Rabalais, "Subplantation Model for Film Growth From Hyperthermal Species: Application to Diamond", Phys. Rev. Lett., 62, 1290, 1989.
2 Y. Lifshitz, G.D. Lempert, E. Grossman, "Substantiation of Subplantation Model for Diamondlike Film Growth from Energetic Species by Atomic Force Microscopy", Phys. Rev. Lett., 72 (17), 2753, 1994.
3 S. Uhlmann, Th. Frauenheim, Y. Lifshitz, “Molecular Dynamics Study of the Fundamental Processes Involved in Subplantation of Diamondlike Carbon”, Phys. Rev. Lett., 81(3), 641, 1998.
4 H.Y. Peng, N. Wang, Y.F. Zheng, Y. Lifshitz, J. Kulik, R.Q. Zhang C. S. Lee and S.T. Lee, “Smallest Diameter Carbon Nanotubes”, Appl. Phys. Lett., 77(18), 2831, 2000.
5 Y. Lifshitz, Th. K?hler, Th. Frauenheim, I. Guzmann, A. Hoffman, R.Q. Zhang, X.T. Zhou, S.T. Lee, “The mechanism of diamond nucleation from energetic species”, Science, 297, 1531, 2002.
6 Y. Lifshitz, X. M. Meng, S.T. Lee, R. Akhveldiany and A. Hoffman, “Visualization of Diamond Nucleation and Growth from Energetic Species”, Phys. Rev. Lett., 93(5), 56101, 2004.
7Y. Yao, M. Y. Liao, Th. K?hler, Th. Frauenheim, R.Q. Zhang, Z. G. Wang, Y. Lifshitz, S. T. Lee, “Diamond Nucleation by Energetic Pure Carbon Bombardment”, Phys. Rev. B, 72, 035402, 2005.