Influence of water and alcohols on photoluminescence of porous silicon

Abstract

The measurements of luminescence spectra were performed on series of porous silicon (PS) samples, obtained in wide range of anodic etching regimes. Photoluminescence (PL) spectra contain two closely spaced luminescence bands. The energy difference between them ∼0.15–0.2 eV depends very slightly on their spectral position. The ratio of the intensities of the two PL bands is monotonously changing with the changes in sample porosity. Thus, in very porous samples only the short-wavelength band is usually observed, while in slightly porous samples only the long-wavelength band is observed. Interaction of PS samples with water at first produces a small decrease of PL band intensities, and then a new band in the range of 0.7 μm appears, which is presumably related to an oxide layer at the surface of PS nanocrystallites. After treating PS in alcohols, the initial band intensity drops and the long-wavelength band disappears completely in less than 1 min. It is discovered that the presence of water contained in the ethanol (even at a content of ∼1%), leads to emergence of a new intensive PL band in the range of 0.7 μm. In very porous samples or after washing or storage of as-anodized PS in water or alcohols, the long-wavelength band is rarely observed experimentally because its intensity is very small.

Defect-related luminescent materials: synthesis, emission properties and applications

“…Earlier defect-related luminescent materials were mainly based upon silica and silica-based materials, including silicatecarboxylate, 17 SiO 2 glass, 18,22 SiO 2 gels, 27,28 SiO 2 spheres, 111,114 organic/inorganic hybrid silicones, [23][24][25] silica nanotubes, 148 molecular sieves, 31,149 etc. [150][151][152][153][154][155][156] As the most promising materials for environmentally friendly phosphors, these kinds of luminescent materials have been the focus of research efforts since the pioneering work of Sailor and co-workers. 17,121 It has been reported that a kind of white phosphor with high emissive broadband spectra (Fig.…”

“…Apart from this, silica gels have been also extensively investigated as defect-related phosphors. Among them, silica aerogels, which are well-known to show photoluminescence generally from the blue to red spectral regions, exhibited several structural defects advantageous to photoluminescent properties, such as a nonbridged oxygen hole center (NBOHC) (described as SiOH -SiO + H; this defect was connected with bands at 1.8 and 1.9 eV), [151][152][153] peroxy linkage (POL) (labeled as ROO , where R represents an unspecified radical or part of the structure), 154 and E 0 center (RSi ) on the basis of the basic emission characteristic band at 2.2 eV in the PL spectra. 152,156 In addition, Hinic´'s group has reported PL spectra measured for two series of silica aerogel sintered at 1000 1C for different time intervals.…”

“…In the PL spectra of silica-based systems, this defect was connected with bands at 1.8 and 1.9 eV. [151][152][153] Unfortunately, the silanol groups (SiOH) are unstable when exposed to ambient air and oxidized slowly to form Si dangling bonds, which form non-radiative recombination centers and influence PL efficiency.…”

From Hydrogen Silsesquioxane to Functionalized Silicon Nanocrystals

“…A significant challenge associated with elemental Si-NCs is the propensity to oxidize in the presence of air and water. 50 Oxidation diminishes the reactive hydride surface, destroys the crystallinity and can influence photoluminescence intensity. However, oxidation can be minimized by covalent functionalization of ligands to the surface.…”

Hierarchical nanofibrous silicon as replica of natural cellulose substance

“…22 It is known that porous silicon matter possesses unique photoluminescence when excited by ultraviolet light. 23,24 The current nanofibrous silicon sheet derived from filter paper is obviously porous with high specific surface areas replicated from the initial cellulose structures. It showed strong blue photo-luminescence under ultraviolet light (Fig.…”