ИСТИНА

Porous silicon (PS) shows interesting optical and electrical properties that can be used in devices such as: photodetectors, gas sensors, biosensors, solar cells among others; but it is necessary to stabilize the PS to be compatible with the c-Si technology. The objective of this work is to study the influence of the thickness of the PS layers after the application of several processes such as dry oxidation (DO), thermal treatment (TT) and functionalization with organic molecules (FOM), specifically sodium fluorescein. PS monolayers were obtained by electrochemical etching of silicon wafers p-type with orientation (100) and a resistivity of 0.01-0.02 Ω • cm, in an electrochemical cell with two electrodes. The electrolyte solution contains: Ethanol: HF: glycerol, anodization solution was kept constant for all processes. The current density was of J = 22 mA / cm2, anodizing times were: 30, 60, 120, 240 and 1200 s. Process such as TT and/or DO and/or FOM with sodium fluorescein at a concentration of 2.4 mM was applied to these PS monolayers for comparison. The porosity percentage (% P) of the first set of PS monolayers was realized by gravimetric technique and the refractive index (n) by using the effective means approximation with the Bruggeman´s formula was obtained. All the PS-layers series were characterized optically after each process by using spectroscopy techniques: UV-Vis-NIR and Photoluminiscence. The thicknesses (0.25, 0.50, 1, 2 and 10 μm) of the monolayers for the first set PS were measured with a profilometer. The fluorescence spectra intensity of PS monolayers with TT, and DO and FOM increase and it is related with the PS monolayers without any process, and there is a shift to lower wavelengths. The reflectance of PS monolayers with TT, and DO and FOM decreases.