Preparation Of Porous Silicon And The Study Of Its Luminescence Properties

Porous Silicon (abbreviated as PS) is a kind of silicon material with nano porous structure. Its porosity is about60%～90%. Porous Silicon can emit visible light at room temperature. This characteristic of the porous silicon makes it a potential material to manufacture silicon-based light-emitting devices, causing a wide range of research interest.In this paper, electrochemical etching method was used to prepare porous silicon. The samples prepared by this method have good uniformity and consistency and can emit visible light at room temperature. Found in the preparation process, it is the preparation conditions (current density, etching time, and etching solution concentration) that affect the photoluminescence (PL) and microstructure of porous silicon. Experimental results indicated:with the other two conditions remain unchanged, the increase of etching time results in a blue shift of luminescence wavelength and the photoluminescence intensity of porous silicon increased at the first, and then decreased. Similarly, with the increase of corrosion current density and the other two conditions stay the same, there is a blue shift of luminescence wavelength and the photoluminescence intensity of porous silicon firstly increases then decreases. With the increase of etching solution concentration, luminescence intensity also increases first and then decreases. However, influence of etching solution concentration on the luminescence peak is relatively complex. When etching solution concentration is smaller than a threshold value, luminescence peak turns to low-energy section when the concentration increases, show as "red shift". When the concentration is higher than the threshold value, luminescence peak turns to high-energy section, show as "blue shift". This threshold value depends on the type and crystal orientation of the crystalline silicon. Through multiple groups of contrast experiments, the optimal conditions for the preparation of porous silicon can be determined. However, for different types of crystalline silicon, the optimal conditions are different. Influence of stability treatments on the luminescence properties of porous silicon is also studied in this thesis. Three stability treatments were used in the experiments and their influence shown as follows:cathodic reduction treatment and acid treatment have a certain degree enhancement on the photoluminescence intensity of the sample. Cathodic reduction-acid treatment, which carries out cathodic reduction treatment to the samples first and then uses acid treatment, compared with the other two individual treatment methods, has a stronger enhancement on the photoluminescence intensity of the samples. The luminescence peaks of the samples treated after the three methods all show blue shift.