| Functional nanomaterials have attracted much attention as the development ofnanotechnology and practical application for nanomaterials. Low-dimensionalsemiconductor nanomaterials are a kind of new functional semiconductor materials,which are obtained by band engineering. Low-dimensional semiconductornanomaterials have been widely used in nano-photonics and nano-electronics fields,such as solar cells, lasers diodes, light emitting diodes and integrated circuits and soon, due to their unique optical, electrical and magnetic properties. Low-dimensionalsemiconductor nanomaterials are the basic unit of nano-electronic devices, and areone of the important materials for the development of high efifciency, low energyconsumption and high-speed optoelectronic devices. However, there are still someproblems to be solved when they are used in practical applications. And theseproblems are mainly focused on: the stability and the potential structuralcharacteristics, physical and chemical properties of low-dimensional semiconductornanomaterials, when they are designed to nano-electronics.Addressed the above problems, we study the mechanical behavior and propertiesof several low-dimensional semiconductor nanomaterials under extreme condition andstrain/adsorption conditions by using molecular dynamics simulation method and thefirst-principles calculations based on density functional theory. These results willprovide be helpful to the synthesis and application of these low-dimensional materials.The main contents and results are presented as following: 1. We study the elastic properties of the cadmium selenide nanowires and thebehavior of carbon nanotubes under high pressure by molecular dynamicssimulations:(1)We study the mechanical behavior of cadmium selenide nanowires in [0001]direction with the wurtzite structure, and found that there is the size dependence ofYoung’s modulus and Poison ratio of these nanowires due to the factor that surfaceeffect increases with the decreasing of the size of nanowires.(2)We study the behavior of single-walled carbon nanotubes under high internalpressure. The results show that single-walled carbon nanotubes are suitable candidatesfor high pressure nanocontainer, and they can resist30to110GPa internal pressure.The ultimate internal pressure that nanotubes can sustain is mainly determined by theradius of the tube, and it is not sensitive to the tube chirality.2. Through the first-principles calculations, we study the electronic structure ofcadmium selenide nanosheet under strain and the structure changes, electrical andmagnetic properties for lithium atom adsorbed on the external/internal surface of thesilicon carbide nanotube:(1)We systematically study the band structure and charge distribution for thehoneycomb structure of cadmium selenide nanosheet under different strain. We foundthat the energy band structure of cadmium selenide nanosheet is sensitive to theapplied strains, and there are different physical propetries with the different strainstate (symmetric and asymmetric strain). When cadmium selenide nanosheet undersymmetric strain (from the compression strain to the tensile strain), there is atransition rfom direct semiconductor to indirect semiconductor. Especially under sym?metrical tensile at e=0.1, nanosheet undergoes a transition rfom semiconductor tometal. Moreover low band gaps comparable to room temperature can be obtainedunder compressive zigzag strain and tensile armchair strain.(2)We systematically study lithium atom adsorbed on the external/internal surfaceof (9adsorbed,0) and (5,5) silicon carbide nanotube. We found spin state with the positions of C, Z and B site of the external surface of (9,0) nanotube and all the adsorbed positions of the external/internal surface of (5,5) nanotube. We conclude thatLi atom doped on SiC nanotube can be used to build high-temperature blocks forspintronic devices. And spin state is not found for the other adsorbed positions. |
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