The Structural Characteristics And The Physical Properties Of Prediction For Low-dimensional CdSe Nanomaterials

Graphene have drawn great attention to science community due to its unique geometry and excellent physical properties since its discovery. The band-gap of original graphene is zero. Efforts have been made on opening the gap in graphene by physical methods, such as strain, by chemical methods or mixing with other atoms. It is found the electrical, magnetic and optical properties will also be affected by those methods. Due to the unique geometry and zero-gap of two dimensional graphene, attention has also been payed to finding other 2-dimensional materials with band-gap. Recently more and more 2-dimensional and 1-dimensional graphene-like structures have been found and studied, such as transition metal oxides, II-VI and III-V compound. CdSe, as an II-VI direct and wide band gap compound semiconductor, has unique physical and chemical properties and have been successful application in optical amplifier, solar cells, photovoltaic devices and biological fluorescent tags. Very recently free-standing semiconductor Cd Se nanosheets with a thickness of 1.4 nm have been successfully synthesized. Although the experiment have synthesized Cd Se nanosheet with a certain thickness, few theoretical studies have been reported the single layer two- and one- dimensionality Cd Se nanosheet and nanoribbon. The main contents of this paper are listed as below: 1. First-principles DFT calculations were carried out to investigate the effect on the electronic properties of Cd Se nanosheet under uniform strain, it is found that the band-gap of Cd Se nanosheet will reduce as strain changes from compressive to tensile. Calculations were also carried out to investigate the effect on the real and imaginary part of complex dielectric function, the index of refraction, and the extinction coefficient Redshift for all peaks of imaginary part of complex dielectric function was found towards the lower energy region under increasing strain. This redshift phenomenon is also found on the extinction coefficient The optical reflectivity, the absorption coefficient, and the energy loss function were also calculated. 2. The electronic and magnetic properties of armchair and zigzag Cd Se nanoribbon are studied. The band gap of ACd Se NRs decreases monotonically as width increases. Bare zigzag Cd Se NRs are ferromagnetic, such phenomenon disappears when edges are terminated with hydrogen. 3. First-principles DFT calculations were also carried out to investigate the effect on structural, electronic and magnetic properties of armchair and zigzag Cd Se nanoribbon under axial strain. We have found that the structural, electronic and magnetic properties of armchair and zigzag are sensitive to axial strain. The binding energies indicate armchair ribbons are more stable than zigzag ribbons with comparable width.