Study Of The Surface State And Energy Contain Property Of Porous Silicon

Porous silicon(PS) is a kind of new material which lead to abroad attention recently. Because of the property of big comparative area, high chemical active, irradiance by light or electricity, explode at low temperature or normal temperature, it has latent applied foreground in the area of photoelectron and compositive electron technology and energy material. Research show, The microstructure produced by specifically preparation technics to corrode the surface, especially the surface silicon of nm size make the key effect. Research on this especial surface layer structure and one another effect of it and adsorbed atom, molecule, cluster of atoms and piece of molecule can make the key effect to figure out PS's explosive property and other specific property.According to this thinking,in this paper it is explored about the relationship between the structure state and macroscopical property on the surface of porous silicon, mainly about energy. Using model chemistry method, first base on the theory and experiment data we bring forward proper model to simulate the surface structure of porous silicon, then make calculations and analyses by the theory and method of quantum chemistry (mostly is the ab initio method which base on equation of HFR). The models of different number of silicon atoms are calculated in this article.That are quantum point model, quantum line model of one dimension, net like model of two dimension, and models which adsorbing H,H2,O,O2,NO3-,ClO4- or both adsorbing two kind of this things. Review the factors of electron state, energy gap, atom charge, bond intensity on different models before and after adsorbing, and calculated the infrared ray of SiHx which are likely to be produced. Result show, the change of energy gap of different model show evidence quantum size effect, surface adsorbing can make this effect more strong, corresponding spectral transition change from infrared ray of crystal silicon to visible light. This trend is the same with the silicon's experiment result, and offer the auspice to explain the quantum limit model of the light porous silicon. Calculation of different adsorbing models show, except H2 can't form the effective chemic adsorption on the surface, other things effect the tiny state of porous silicon by chemic adsorption, the representation is new distribution of atom charge, charge divert to the adsorbing bond, weaken the bond intension between the surface silicon atom and the inner silicon atom, and weaken some bond of adsorbed molecule, make them more easy to rupture. As the result of the one other effect between the nm size surface and adsorbed things, can produce many high active things on the surface immediately, this things include SiHx, SiOx, pieces of molecule, even atom H, O or cluster of silicon atoms which rupture instantly, to newly maked surface, this things do not be oxidation or escape, can reach a certain concentration. When meet with sparkle or current, will likely to arose exquisite oxidation reaction, release a great deal of energy at the moment. To be short, if there distribute nm structure at the surface of porous silicon, there will be a lot of unsaturated silicon atoms, a free group of silicon and pieces of molecule and a certain concentration of H, a series of oxidation reaction produced by them is the direct and inner reason of porous silicon's explosive property.