Formation of carbon nanostructures with Ge and SiC nanoparticles prepared by direct current and radio frequency hybrid a
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T. Hirata, N. Motegi, R. Hatakeyama, and N. Sato Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
T. Mieno Department of Physics, Shizuoka University, Shizuoka 422-8017, Japan
N.Y. Sato and H. Mase Department of Electrical and Electronic Engineering, Ibaraki University, Hitachi 316-0033, Japan
M. Niwano Research Institute of Electrical Communication, Tohoku University, Sendai 980-0813, Japan
N. Miyamoto Department of Electrical Engineering, Tohoku Gakuin University, Tagajo 985-0873, Japan (Received 26 February 2000; accepted 10 July 2000)
Carbon nanocage structures with Ge and SiC nanoparticles were synthesized by direct current and radio frequency (dc-rf) hybrid arc discharge of C, Ge, and Si elements. High-resolution images showed the formation of Ge and SiC nanoparticles and nanowires encapsulated in carbon nanocapsules and nanotubes. The growth direction of the Ge nanowires was found to be 〈111〉 of Ge, and a structure model for Ge/C interface was proposed. The present work indicates that the various carbon nanostructures with semiconductor nanoparticles and nanowires can be synthesized by the dc-rf hybrid arc-discharge method.
Various carbon nanocapsules filled with Au, LaC2, Co, Fe, Ni, Cu, CrCx, MoCx, MoO3, WCx, WO3, TiC, and other elements have been synthesized by an ordinary arc-discharge method,1–5 which are expected to be used for both scientific research and future device applications such as cluster protection, nano-ball bearings, nanooptical–magnetic devices, catalysis, and biotechnology. Although these metal nanoparticles had been successfully enveloped inside the spherical graphene sheets, few works have been reported for encapsulation of semiconductors such as Si, SiC,6,7 and Ge.7,8 Although semiconductor nanoparticles are expected to show luminescence by the quantum size effect, they are easily oxidized by exposure to air. Encapsulation of these semiconductor nanoparticles by the graphene layers is expected to provide a stable surface structure and new properties. Recently we have succeeded in the formation of carbon nanocapsules by thermal decomposition of poly(vinyl alcohol) with SiC nanoparticles at 500 °C in an Ar a)
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J. Mater. Res., Vol. 15, No. 10, Oct 2000 Downloaded: 16 Mar 2015
gas atmosphere. 6 , 7 We have also produced Pdintercalated onions by electron-beam irradiation.9,10 These materials are expected to be used as solid-state lubricants and magnetic materials, respectively. However, the starting materials of SiC nanoparticles and Pd clusters should be prepared by other methods before producing the carbon nanocapsules, and a new method for the formation of nanocapsules filled with semiconductor nanoparticles is needed. The purpose of the present work is twofold. The first is to synthesize carbon nanocapsules with semiconductor nanoclusters by direct current and radio frequency (dc-rf) hybrid arc discharge. In the present work, Ge and SiC with the band structures of indirect transition
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