Enhancement of physical properties of stain-etched porous silicon by integration of WO3 nanoparticles

Abstract

In this work, we report on the passivation of porous silicon (PS) by tungsten trioxide (WO 3 ) nanostructured thin films deposited via dip-coating of PS in tungsten hexachloride and water/ethanol solution. Structural analysis by Fourier transform infrared spectroscopy showed a partial disappearance of SiH x and Si-O-Si peaks after WO 3 thin film deposition on the PS due to the replacement of H atoms by WO 3 . Additionally, PS/WO 3 sample revealed weakly intense peaks which can be ascribed to O-W-O and W=O bridging bonds. Morphological analysis by atomic force spectroscopy showed the coverage of the PS surface by a nanostructured thin film of dense WO 3 nanoparticles with a size ranging from 40 to 60 nm. The photoluminescence signal intensity of PS/WO 3 samples presents a continuous increase as a function of the immersion time in the precursor solution. This is attributed to a better decoration of the PS surface by WO 3 nanoplatelets and a decrease of surface recombination velocity (200 x 10 2 cm/s for untreated silicon, 137 x 10 2 cm/s for PS and 99 x 10 2 cm/s for PS/WO 3 samples). Hence, a ~ 50 % improvement in the effective lifetime of minority carriers is obtained.Moreover, the deposited WO 3 contributed not only to the passivation of PS, but acted as an antireflection layer which enhanced the optical properties of PS by reducing the reflection of light. These obtained results confirmed the benefits of using WO 3 thin film as passivation/antireflection coating for possible solar cell application.

Room temperature NO2 gas sensor based on stain-etched porous silicon: Towards a low-cost gas sensor integrated on silicon

“…In order to confirm this observation, FTIR spectra of freshly prepared and oxidized PS samples were performed (Fig. 4) showing the vibration bands attributed to SiHx and Si-O-Si stretching mode at 2112 cm -1 and 1092 cm -1 respectively, the SiH2 scissors mode (907 cm -1 ), the Si-Si stretching mode (628 cm -1 ), SiHn and O-SiHx wagging mode at 672.7 cm -1 861 cm -1 respectively [18]. Comparing the two spectra, we notice the reduction of the SiHx peak at 2112 cm -1 against the increase in Si-O peak intensity confirming the PS surface oxidation.…”

Study of n-WO3/p-porous silicon structures for gas-sensing applications

“…3 (a)). The two spectra show almost the same bands with a clearly reduction of SiHx and Si-O-Si peaks intensities for the WO3/PS sample suggesting the replacement of H atoms by WO3 molecules [26]. After zooming different zones (A, B, C) in the spectral region (400 cm -1 -1000 cm -1 ) and the deconvolution of different peaks, the W-O bands are depicted.…”

“…The WO3 solution with a concentration of 0.035 mol/L was prepared using WCl6 powder, 50 % ethanol and 50 % water under stirring for 3 h at ambient temperature. Finally, the solution was stored in air during 7 days before being used [26][27].…”

“…2 (a). We distinguish the principal recorded vibration bands: SiHx stretching mode at 2112 cm -1 , Si-O-Si stretching mode at 1092 cm -1 , SiH2 scissors mode at 907 cm -1 , Si-Si stretching mode at 628 cm -1 , SiHn wagging mode at 672.7 cm -1 and O-SiHx wagging mode at 861 cm -1 [26].…”