Excitation Of Si_xN_y(x,y=1,2) Molecule Under External Electric Fields

In recent years, with the development of photoelectric integrated circuits, researching luminescencematerials has become more and more important. There are many difficulties on technologies for traditionalluminescence materials, like high price and it is difficulty to find the compatible lance for them and so on.More and more scientist start research the silicon-based luminescence materials since Canham found theporous silicon can emission visible light. At present, researching luminescence from silicon-based materialsunder the action of external electric field or light field has been an important research subject. It is provedthat azotized silicon materials are important silicon-based materials luminescence materials, however, itsmicrostructure is still uncertain and there is also much controversy for the theory of luminescence. It isknown that the properties of molecule are decided by the structure, and so the properties of materialsaccount for the properties of the molecules and the excited states under external electric field are critical tothe study on luminescence. At present, the ground state properties of molecules have been researchedextensively in theory but the study on excited states of molecules is insufficient. Therefore, the study onexcited states of molecules under external electric or light field at the level of atom and molecule is veryimportant and significative.In this paper, the microstructures of some main silicon-rich Si_xN_ymolecules have been studied and theexcited states also been analyzed. All the calculations are executed using Gaussian03program package.Density function theory （DFT） is an effectual and convenient method to research the ground structure andthe excited properties. Therefore, at first the geometry of Si_xN_ymolecule （SiN, SiNN, Si₂N） is optimizedusing DFT （B3P86） method. Then, on the basis of optimum structure, the excited properties of Si_xN_ymolecule are calculated using TD-DFT method under no external electric field as well as external electricfield. The oscillator strength f, transition electric dipole moment μ, excited energy E and absorptionspectrum λ also been calculated. Illustrate luminescence characteristics and mechanism of the SiNmolecular in theory from taking the calculated value compared with the experiment value, But for （SiNN,Si₂N） molecules, taking the calculated values compared with the experiment values proof the structure ofmolecular and the structure constant, and more verify the luminescence characteristics and mechanism forthe molecules. On this basic, the possibility and mechanism of luminescence for Si_xN_ymolecules has beenanalyzed and token a compare between theoretical value with experiment value, found them correspondvery well, this improves the luminescence properties of azotized silicon molecules in the theory.