Study On The Photoluminescence Of Porous Silicon Prepared By Anodization Methods With Positron Annihilation Technique

A great drawback is the fact that silicon, the basic material for photonics which is the hot field of research and technology, is an indirect-gap semiconductor which emits light in the infrared and at very low efficiencies. Unlike bulk silicon, a spectacularly dull material, porous silicon (PS) with ultra small silicon nanoparticles and nanowires are spectacularly efficient at emitting visible light at room temperature. In addition to being ultra bright, reconstituted films of particles exhibit stimulated emission. Because of its large internal surface area, porous silicon is an attractive material for chemical and biological sensing applications.The basic methods of fabricating luminescent porous Si films, which is simple design and cheap, is electrochemical anodic corrosion of silicon in a solution of hydrofluoric acid. Based on the technique, we do the research on the current-voltage characteristic of Si-HF electrolyte junctions in the process of PS fabrication with the electrochemical station. We attain the PS with high porosity and thickness when current below a critical value, the electrochemical polish occurs for instead when current higher than that.With the current density specified to the anodization of PS, samples are prepared under different oxidizing current density are characterised by the positron lifetime spectrometer and VUV spectroscopic, using positron annihilation technique (PAT) study on the photoluminescence properties of PS.In this thesis, we compare the porous silicons which are prepared under two kinds of anodization conditions of pulse and constant voltage. The results show that the pulse method is conducive to the corrosion process of the growth of holes to maintain a certain direction. And the silicon nanowires formed in the layer of porous silicon can not easily be eroded. The light-emitting of porous silicon is significantly enhanced by the mean of pulse method, which is superior to the traditional galvanostatic method.PS with Si-Ag bonds passivation can be prepared by using magnetron sputtering. We obtain PS with different thickness of silver film on the surface by changing the sputtering time. According to the results of photoluminescence spectroscopy and Doppler broadening, defects in the silver film deposited on the PS surface change with different sputtering time, and the carriers radiative recombination centers increase with the defects. It makes the PL of the PS enhancing. PL would be weakened if the silver film is too thick due to the losses in the silver layer.