The Research On Fabrication Method And Photoluminescence Property Of Porous Silica With Concave-convex Structure On Si Wafer

As a silicon-based nano-material with light-emitting function, porous silicon which is paid widely attention with good photoluminescence and electroluminescence properties at room temperature is easily compatible with silicon based technology, which can realize massively and the ultra large-scale silicon-based photo-electronics devices. However, universal method preparing porous silicon is still using hydrofluoric, and the stability problem and reproducibility of photoluminescence of porous silicon remains unsolved. Moreover, poisonous hydrofluoric acid is a potential hazard to operator and the environment. Seeking for solution which is simple preparation condition, good duplication, the stable illumination is the hot spot at present. We attempts to use one kind of new preparation method - metal assistance chemical reaction etching to gain porous silica, and the structure of porous silica is different from the structure of traditional porous silicon. Moreover, the illumination performance is more stable and higher efficiency. Using some measure methods, such as OM, SEM, TEM, AFM, EDAX, PL has characterization microscopic structure and photoluminescence property of porous silica. We prior to research influence of the preparation technological conditions on the microscopic structure and photoluminescence property, and has discussed its unique structure formation mechanism and the photoluminescence mechanism.The porous silica is the SiO_x thin film crack with concave-convex structure, and the obvious periodicity and the directivity. Adjusting the density of HNO3 can control arisen time of porous silica concave-convex structure. Neither higher or less of Density of HNO3 has been able to produce the concave-convex structure. Under certainly etchant condition, the adjustment of etching time may control the structure of evolution.The crack first appears in the superficial defective area. As effects of the reaction heat and the air bubble together, which cause the huge stress and the strain in the silica thin film, and result in crack in some stress critical threshold value, then form the concave-convex structure. The crosswise corrosion can cause the concave-convex structure to thin, upwarping, even fall off. Its directivity is possible related to the wafer.The photoluminescence peak position of porous silica was stable in certain etchant, but the intensity of photoluminescence increased firstly and then decreased. It will be more conducive to gain photoluminescence at room temperature, when the mixture of HNO₃ and HC1 acts as etchant. The change of PL was not related to the sizes of structure. After one year the sample exposed in the air, the peak position didn't change, while intensity increased up to threefold. The sizes change and the PL spectrum of PSN were not positive connection, we eliminated possibility that the photoluminescence originated from the quantum effect. Combined our experimental results, we discussed the photoluminescence of porous silicon maybe origin from oxygen related defects or vacancy.