Nanostructure Design And Calculation Of Silicon Surface

Using first-principles DFT method,several different types of Si and Ge nanostructures on the Si?111?surface were studied,including their geometrical structures,electronic structures and optical properties.The calculated results of the different types of Si nanostructures show that the order of their stability of the nanostructures on the Si?111?surface is pit>nanobar>island>adsorbed quantum dot,and the optical property calculations show that the nanostructural modification on the Si?111?surface can enhance the optical absorption of the silicon surface but the position of the maximum absorption peak didn't have obvious shift.The maximum peak of optical absorption appeared in the near UV 314 nm.Moreover,in the ultraviolet region,the Diamond-like on the Si?111?surface can enhance the optical absorption by a maximum percentage of?30%.In the visible light range,the optical absorption of the Si₁₄@Si₆₄ nanostructure is the largest,and the enhanced percentage of optical absorption with respect to Si?111?is about 67%.The calculated results of different types of Ge nanostructures on the Si?111?surface show that the stability of three types of Ge nanostructures is in the order,strip>grating>hexagonal island.The calculated results of optical absorption show that the optical absorption intensity of the strip nanostructure is higher than those of hexagonal island and grating nanostructure.Although the Si?111?surface were modified by the Ge quantum nanostructures with different shapes,the position of the absorption peak of the Si?111?substrate is not changed obviously,and in contrast to the Si nanostructures,the Ge nanostructures on the Si?111?surface decrease the optical absorption of the Si surface.