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Theoretical Calculation of Pure and Doping with Transition Metals Sic Nanoribbons

Author: LiWei
Tutor: LiZeSheng
School: Harbin Institute of Technology
Course: Physical and chemical
Keywords: Silicon carbide nanoribbons Density funetional theory Gas sensors Conductivity Chemical modification
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 31
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Abstract

The discoveries of nano materials have opened a new era of nano time, especially the discovery of carbon base materials, such as carbon nanotubes, graphene, and fullerene have shocked the world, also have brought us a good time in which carbon materials take the leading roles. Because of superior performance of the carbon base nano materials, scientists turned to the other composite nano scale materials, such as silicon carbide nanoribbons. The structure and properties of silicon carbide nanoribbons, in particular its unique electrical and magnetic properties, could have many important applications in the field of electronic devices.In this thesis, I have studied the adsorption of small molecules and transition metal doping behavior using the density functional theory based method, and firstly analyzed its application prospect in the field of gas sensors, and hope to control the lectrical and magnetic properties of silicon carbide nanoribbons through the transition metal doping, furthermore to broaden applications of silicon carbide nanoribbons. In the work, based on the study on molecular adsorption I have found that nitric oxide, nitrogen dioxide, formaldehyde, and carbon monoxide have great influence on the electronic structure of silicon carbide nanoribbons, after adsorption the conductivity increases significantly. Previous researches have shown that whether the semiconductor sensors can detect the molecules is on basis of the changes in conductance. Therefore, silicon carbide nanoribbons can be used as gas sensors which can detect these four kinds of molecules. For the adsorption of carbon dioxide, although its electrical conductivity has also been increased, but the change is very weak compared to the other cases. The adsorption of water vapor, ammonia, hydrazine, and methanol vapor are very similar, the electrical conductivities do not change much.As the pure silicon carbide nanoribbons cannot well detect carbon dioxide. However, the detection and adsorption fixation of carbon dioxide are difficult while with important practical significance. The chemical modification of materials has been an important means to seek new materials for material scientists, in this thesis I construct a model of transition metal platinum doping system, which can adsorb carbon dioxide. The defect caused by platinum makes the platinum a very strong chemical active center, its rich d orbitals make the adsorption of molecules more favorable, and the conductivity of the material has significant changes due to adsorption of carbon dioxide, so doped system can be used as sensing material for carbon dioxide.Chemical modification can improve the performance of materials, many excellent materials were obtained through chemical modification. firstly, I studied the structure and performance of system, which was doped by the first transition metal. By calculating I have not only got different band gap semiconductors, but also the conductors, while some ones also be magnetic due to the doping so that there will be an important application prospect in the field of spin electronic devices.

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