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Carbon Features on 4h and 6h-Sic Using Atomic Force Microscopy

Essay by   •  December 5, 2010  •  Essay  •  927 Words (4 Pages)  •  934 Views

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Abstract

Carbon nanotubes are considered to be the building blocks of nanotechnology on the basis of their nanosize and unique electrical properties. The physical and electrical characteristics of carbon nanotubes establish them as excellent devices to be utilized in the advancement of technology. Much research has been dedicated to the characterization and identification of carbon nanocaps. In the present research, molecular beam epitaxy was employed to produce 1 sample of 4H-SiC and 2 samples of 6H-SiC. The 4H- SiC and 6H-SiC were annealed at 1400„aC at a base pressure of 10-5 torr. Atomic Force Microscopy measured the topography and electrical characteristics of the various SiC sample surfaces with sub nanometer scale resolution. Five regions on each sample were chosen for AFM analysis as well as production of voltage curves for the respective areas. Regions on the AFM images indicated two distinct types of carbon features. Circular carbon features on the areas on the 4H and 6H were observed and the voltage curves of the respected regions proved the areas to exhibit rectifying contact as well as practical ÐŽ§nonЎЁ-linear contact. In certain regions on the 6H-SiC, carbon features were observed to grow in a triangular, flat manner. Voltage curves of the areas proved the sample to exhibit rectifying contact.

Introduction

Carbon nanotubes were discovered in 1991 by Dr. Sumio Iijima at the NEC Corporation in Japan.2 While searching for buckyballs, Iijima found "whiskers" on the surface of the graphite layer which he later identified as carbon nanotubes or CNTÐŽ¦s. CNTÐŽ¦s are cylindrical carbon molecules with properties that make them potentially useful in extremely small scale electronic and mechanical applications. Each nanotube is a single molecule made up of a hexagonal array of covalently bonded carbon atoms, the strongest existing liaison. 7 Single wall nanotubes (SWNT) consist of one cylinder, whereas multi wall nanotubes (MWNT) comprise several (7 to 20) concentric graphene cylinders. A number of techniques including arc-discharge, laser ablation and chemical vapor deposition can be utilized to synthesize these materials. The method employed is usually dependent on the type of SiC used as well as the given experimental conditions.8 The physical and electrical characteristics of carbon nanotubes establish them as excellent devices utilized in the advancement of technology. CNTÐŽ¦s distinct electrical properties can be attributed to the quantum confinement of the electrons in the circumference of the tube. The sp2 hybridization of the molecule enables the delocalization of the free valence electron which can result in movement of a current.6 Their properties are a mix of diamond and graphite: they get the strength and thermal conductivity of diamond, and the electrical conductivity of graphite, all while being light

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