Evidence that blue luminescence of oxidized porous silicon originates from SiO2

Abstract

We have analyzed red and blue luminescence from porous silicon as a function of oxidation parameters and feature dimension determined with an atomic force microscope. We have found correlation between blue luminescence intensity and the increase in feature size caused by oxidation. We have further shown that blue luminescence, is identical, with respect to spectrum and fast decay, to that of high microelectronic quality SiO, grown on crystalline silicon using dry oxygen plus an organic chlorine compound. Thus, we conclude that blue luminescence originates from SiOZ film rather than from the silicon nanocrystals in the porous material. Intensity enhancement, as compared to SiO, on crystalline wafers, comes from the gigantic surface area of porous silicon.

Thermal quenching properties of ultraviolet emitting centers in mesoporous silica

“…1,2 On the other hand, blue-green emission is ascribed to surface-related defects, including both C or OH groups adsorbed at the surface of the porous material. [1][2][3][4][5][6] As regards silica-based nanostructered materials, red, green, and blue emissions from silica nanoparticles, mesoporous silica, and silica nanotubes were reported with strong similarities with the spectroscopic features observed in nanoscaled silicon. [7][8][9][10] Since the thickness of the bulk silica walls in nanostructured silica materials ͓ϳ1 nm ͑Ref.…”

“…1 Beside the technological interest, the topic is also relevant from a basic research point of view, since the attribution of these optical features to quantum confinement effects or to defect-related mechanisms is still debated. [1][2][3][4][5][6] Concerning porous and nanocrystalline silicon, the emissions in the red to near-infrared region ͑2.1-1.3 eV͒ depend on the dimensions of the Si nanocrystals, providing experimental evidence of the role of the quantum confinement effects. 1,2 On the other hand, blue-green emission is ascribed to surface-related defects, including both C or OH groups adsorbed at the surface of the porous material.…”

Nanoporous silicon tubes: the role of geometry in nanostructure formation and application to light emitting diodes

“…The F band luminescence, usually centered between 420 and 500 nm, decays on the nanosecond time scale. This can be observed on porous silicon samples aged in air or intentionally oxidized, and is thought to originate from structural defects in the silicon nanocrystal oxide shell, or from the luminescence of very small silicon nanocrystals [19,39,[69][70][71][72]. Other PL bands have been previously reported for porous silicon: the so-called UV band (centered around 350 nm), and the R band (ranging from 1100-1500 nm) [59].…”

“…The spectrum obtained at the necklace has a higher S/F intensity ratio compared to the spectrum obtained at the tube tip/walls. The F band is related to the defects at the silicon/silicon oxide interface [69,70,73]. The necklace region corresponds to the area where the tube is actively forming.…”

Effect of hydrofluoric acid concentration on the evolution of photoluminescence characteristics in porous silicon nanowires prepared by Ag-assisted electroless etching method

“…I. 23,35,37,38 Comparing the PL spectra before and after HF treatment, we believe that existence of oxide plays a significant role in changing the emission property of the nanowires.…”