Yttrium oxide passivation of porous silicon for improved photoluminescence and optoelectronic properties

This paper reports on the effect of yttrium oxide as a novel treatment to improve the photoluminescence intensity and stability of porous silicon (PS). Yttrium oxide (Y2O3) was incorporated into the PS layers by impregnation method using a saturated aqueous solution. The penetration of Yttrium into the PS microstructure was examined using the Energy Dispersive X-ray spectrometry (EDS) and the Backscattered Electron Detector (BED-C) for composition imaging and analysis. The morphology of the front surface was studied using a Field Emission Scanning Electron Microscope (FESEM). The deposited yttrium oxide onto the PS layers was thermally activated to passivate efficiently the silicon dangling bonds, and prevent the porous silicon from huge oxidation. The photoluminescence (PL) peak intensity of impregnated PS was increased noticeably compared to the as-prepared untreated PS. Unlike the as-prepared PS photoluminescence dependence with aging, the yttrium-passivated PS layers PL peak shows no shifts during aging allowing a high stability. Furthermore, we obtained a significant improvement of the effective minority lifetime (Teff) after a short anneal at 600 °C, while increasing the temperature reduces noticeably the passivation properties. The improved surface passivation experienced after the thermal annealing can be ascribed to yttrium diffusion into the PS layer, with a resulting redistribution of yttrium oxide and subsequent passivation of silicon dangling bonds in the sub-interface region, this was confirmed by EDS analysis. The internal quantum efficiency (IQE) measurements were performed to study the optoelectronic properties of the processed monocrystalline silicon substrates

iTRAQ proteomic analysis of extracellular matrix remodeling in aortic valve disease

Degenerative aortic stenosis (AS) is the most common worldwide cause of valve replacement. The aortic valve is a thin, complex, layered connective tissue with compartmentalized extracellular matrix (ECM) produced by specialized cell types, which directs blood flow in one direction through the heart. There is evidence suggesting remodeling of such ECM during aortic stenosis development. Thus, a better characterization of the role of ECM proteins in this disease would increase our understanding of the underlying molecular mechanisms. Aortic valve samples were collected from 18 patients which underwent aortic valve replacement (50% males, mean age of 74 years) and 18 normal control valves were obtained from necropsies (40% males, mean age of 69 years). The proteome of the samples was analyzed by 2D-LC MS/MS iTRAQ methodology. The results showed an altered expression of 13 ECM proteins of which 3 (biglycan, periostin, prolargin) were validated by Western blotting and/or SRM analyses. These findings are substantiated by our previous results demonstrating differential ECM protein expression. The present study has demonstrated a differential ECM protein pattern in individuals with AS, therefore supporting previous evidence of a dynamic ECM remodeling in human aortic valves during AS development

Enhancement of porous silicon photoluminescence using vanadium pentoxide (V 2

A new method has been developed to improve the photoluminescence intensity of porous Silicon PS. In this treatment we used vanadium, for the first time, to passivate porous silicon. Thermal evaporation of (V2O5) onto PS layer, followed by a thermal treatment at 100°C, 200°C, 300°C and 400°C for 15 min under oxygen flow, can increase the intensity of the photoluminescence of PS. Vanadium oxide covers the nanoparticles of silicon without changing the wavelength distribution of the optical excitation and emission spectra. Changes in the surface morphology induced by thermal treatment were investigated by atomic force microscope (AFM) showing an increase of the nanoparticles dimensions compared to the initial dimensions of the PS nanostructure. The reflection spectra of PS, before and after treatment with (V2O5), performed in the 300–1200 nm wavelength range and compared to a virgin mc-Si wafer, showed an important decrease of the reflectivity by this new treatment

The effect of ultrasonic wave amplitude on the physical properties of zinc oxide (ZnO) deposited by ultrasonic spray method

International audienceIn this study, high quality zinc oxide (ZnO) thin films, with improved properties, were prepared by a cost-effective ultrasonic spray pyrolysis technique via a careful optimization of the used ultrasonic wave amplitude. The deposition process was performed on glass substrate and were subsequently annealed at 400 °C. We investigated the effect of various ultrasonic wave amplitude on the structural, surface morphology, optical and electrical properties of the obtained thin films, after varying the applied wave amplitude. Furthermore, deposited thin films were studied by means of XRD, UV–vis spectrophotometer, scanning electron microscope, and four-point probe technique. XRD analysis confirmed that obtained ZnO thin films have polycrystalline structure and a wurtzite (hexagonal) phase, with a c-axis preferred orientation (0 0 2). The crystallite size was about 23–30 nm. The SEM micrographs of the surface morphology show uniform, homogenous and dense films with granular structures. The films thicknesses were found to be dependent on the used wave amplitude; they were ranged from 184 to 423.5 nm. In addition, the optical properties of the deposited thin films reveal that the films are highly transparent in the visible region above 80%, while the value of energy band gap varies from 3.24 to 3.27 eV. The Electrical properties investigation revealed a resistivity around 10-3 Ω.cm, showing also a non negligible dependency with the wave amplitude tuning. We obtained an improvement in the carrier concentration (1.6 × 1020–3.9 × 1020 cm−3) and mobility (4.2–15 cm2/V.s) with the ultrasonic wave amplitude rising. High quality ZnO thin films with enhanced properties are in demand and have a large wide of applications in optoelectronics and solar cells. © 2021 Elsevier B.V

Yttrium oxide passivation of porous silicon for improved photoluminescence and optoelectronic properties

This paper reports on the effect of yttrium oxide as a novel treatment to improve the photoluminescence intensity and stability of porous silicon (PS). Yttrium oxide (Y2O3) was incorporated into the PS layers by impregnation method using a saturated aqueous solution. The penetration of Yttrium into the PS microstructure was examined using the Energy Dispersive X-ray spectrometry (EDS) and the Backscattered Electron Detector (BED-C) for composition imaging and analysis. The morphology of the front surface was studied using a Field Emission Scanning Electron Microscope (FESEM). The deposited yttrium oxide onto the PS layers was thermally activated to passivate efficiently the silicon dangling bonds, and prevent the porous silicon from huge oxidation. The photoluminescence (PL) peak intensity of impregnated PS was increased noticeably compared to the as-prepared untreated PS. Unlike the as-prepared PS photoluminescence dependence with aging, the yttrium-passivated PS layers PL peak shows no shifts during aging allowing a high stability. Furthermore, we obtained a significant improvement of the effective minority lifetime (Teff) after a short anneal at 600 °C, while increasing the temperature reduces noticeably the passivation properties. The improved surface passivation experienced after the thermal annealing can be ascribed to yttrium diffusion into the PS layer, with a resulting redistribution of yttrium oxide and subsequent passivation of silicon dangling bonds in the sub-interface region, this was confirmed by EDS analysis. The internal quantum efficiency (IQE) measurements were performed to study the optoelectronic properties of the processed monocrystalline silicon substrates