Correlation between reflectivity and photoluminescent properties of porous silicon films

Abstract

Porous silicon (PS) layers were formed on p-type. <lOa) oriented. 1-5 n em resistivity Cz silicon wafers by electrochemical etching in an HF:C 2 H s OH (1:2 by volume) electrolyte at room temperature at a constant current density 20 mA/cm 2 • The etching duration was varied to achieve PS layers of different morphologies and thicknesses. Both the photoluminescence (PL) and the total diffused reflectivity spectra of the PS layers were measured. It was found that for the PS layers grown for etching durations of less than 90 s the PL emission is insignificant and reflectivity is quite low. Such PS layers can be used as antireflection coatings (ARC) on solar cells. The PS layers formed for etching durations greater than 90 s show a significant PL emission in 500-800 nm range with peak lying in 630-660 nm wavelength range. When etching duration increases from 90 s to 8 min the PL intensity increases and the PL peak shows a blue shift. With further increase in etching duration the PL intensity decreases and PL peak shows a red shift. The reflectivity of the photoluminescent layers increases with etching duration showing a highest value for a sample grown for 8 min. Further increase in etching duration up to 20 min the reflectivity decreases and then increases. Striking observation is that both the PL emission intensity and reflectivity in the wavelength range of 550-800 nm are maximum for the PS layer grown for the etching duration of 8 min.

Visible Photoluminescence of Variable-Length Zinc Oxide Nanorods Embedded in Porous Anodic Alumina Template for Biosensor Applications

“…The deviations from a perfect match may be caused by partial overlapping of ZnO PL bands and additional PL from the PAAO matrix. Interestingly, similar experiments in porous silicon layers [38] on Si substrate resulted in positive correlation between PL and reflectance, which is opposite to our observations. This discrepancy motivates further research, but likely can be explained by different phase flips of electromagnetic wave reflection from different interfaces in multilayer systems.…”

“…This is similar to observations on Si-ZnO core-shell nanowires [36], where samples with low reflectivity had highest PL intensity. However, the results are opposite to observations in porous silicon layers [38], where positive correlation between the reflectivity and PL was reported.…”

Growth of Zinc Oxide Nanocombs on Porous Silicon Layer by Thermal-Evaporation Method

“…The right, high-intensity PL peak at 637.5 to the PS layer [33,34]. The blue shift in the PS layer is attributed to the quantum confinement electrons in nanosized particles in the PS addition, the observed emission at 637.5 nm surface oxidation by ZnOnanocomb deposition emission peak for the PS layer containing 605 nm in the visible region is related to the intrinsic structural defects resulting from Zn…”

“…The PS layer Advances in Materials 2015; 4(2): [30][31][32][33][34][35] 637.5 nm is attributed the PL peak of the confinement effect of layer [30,35]. In nm is related to the deposition [36].…”

Correlation between reflectance and photoluminescent properties of al-rich ZnO nano-structures

“…The wavelength value for the minimum reflectance of the annealed samples is blue shifted with the annealing temperature. This blue shifting is due to the decrease of the optical thickness of the AZO film with the increase of the annealing temperature [36]. The dependency of the surface roughness on annealing temperature of AZO films, measured using atomic force microscopy (AFM), is shown in Fig.…”