Fabrication Of Porous Silicon (PS) And Research On Photoluminescence Of PS

Silicon-based luminescence materials have become a new-style optoelectronic materials which are developing rapidly in recent years, and porous silicon (PS) has received considerable attention because of its room temperature photoluminescence (PL). PS light-emitting materials have prospects in silicon-based optoelectronic materials area and will play an important role in optoelectronic integration as long as we realize PS high efficiency and stable photoluminescence (PL) and electroluminescence (EL) properties.In this thesis, p-PS layer was obtained by conventional electrochemical anodization of a boron-doped p-type Si wafer at constant current density. Three-dimensional (3D) fluorescence spectrum from 200nm to 700nm for PS was investigated at room temperature, and visible PL peaks of PS were indicated by 3D fluorescence spectrum. The dependence of room-temperature visible photoluminescence of porous silicon and its microstructure on the anodization conditions (etching time, HF concentration, current density and doping density of substrates) were studied systematically. The results showed that the increase of etching time and current density, and the decrease of HF concentration and doping density resulted in a blue shift of luminescent wavelength and a complex change of PS PL intensity. All the results were explained with the quantum confinement effect (QCE) and the formation mechanism of PS.n-type porous silicon (n-PS) has been formed usually using the normal method of anodization of n-silicon substrates in HF electrolytes with illumination. In this letter, an alternative method for the fabrication of n-PS based on the Hall effect was developed novelly. Room-temperature visible photoluminescence of n-PS and its microstructure were investigated. Desirable visible photoluminescence emissions were demonstrated in n-PS, and when the external magnetic-field intensity increased, the porosity and the thickness of n-PS layer were also increased. An applied magnetic field on etching process enhanced the luminescence efficiency of preparing n-PS. Furthermore, a new method of evaluating the aperture distribution and surface porosity of PS samples was presented by digital picture processing and analysis technique based on SEM images of PS, and the calculative results were close to the experimental ones.In the present work, an electrochemical deposition technique in low current density was applied to prepare PS samples with Ag deposition for the purpose of substituting the stable Ag-Si bonds for H-Si on the surface of PS. The experimental results indicated the current density and hydrophilicity or hydrophobicity of PS surface had influence on Ag depositing forms and uniformity. Ag deposited on PS surface to form Ag-Si bonds, and the stable Ag-Si bonds can inhibit the formation of -Si effectively which were testified to be non-luminescence centers, therefore, inhibit the degradation of PL intensity. In addition, excessive Ag deposition had a quenching effect on room-temperature visible photoluminescence of PS.