Visible Light Emission from Free-Standing Filament Crystals of Silicon

Abstract

We present the results of a photoluminescence study in naturally grown filament‐like silicon crystals. It is shown that with the decrease of filament diameter from few tens to 0.1 μm, the photoluminescence spectra transform from the ones of bulk silicon to completely new spectra. The spectra at 4.2 K consist of the narrow 1.139 eV band and several very wide visible (red, yellow, green, and blue) bands with the maximum position ranging from 1.7 to 2.9 eV. The bands of visible photoluminescence do not markedly change with the increase in temperature up to 300 K, while the 1.139 eV band disappears. The most striking result is the appearance of visible light emission from crystals with transverse size much larger than the Bohr radius. The results obtained are discussed together with our previous ones obtained for these crystals, and a possible model of the filament crystal structure as well as the origin of visible photoluminescence are suggested.

New infrared luminescence band in silicon nanowires

“…The relative intensity of the N-band increases with the decrease of the wire diameter, while the bands characteristic for bulk silicon decrease and disappear completely in the wires with diameters down or about 100 nm [7]. This suggests that this band may be attributed to the envelope of cellular structure.…”

“…While the light-emitting characteristics of bulk silicon are unfavorable for the creation of optoelectronic devices, the luminescent characteristics of nanoscale silicon objects are much more promising. The visible luminescence [2] and substantial transformation of IR exciton luminescence [7] found in nanowires indicate an essential change in the energy band structure and possibly in the crystalline structure. Visible luminescence may be accounted for by dimensional quantization, but this cannot be the reason for the observed changes in IR-luminescence spectra that appear with the decrease of size down to nanometer scale.…”

“…Visible luminescence may be accounted for by dimensional quantization, but this cannot be the reason for the observed changes in IR-luminescence spectra that appear with the decrease of size down to nanometer scale. We have shown earlier [7] that the IR-excitonic spectra of silicon wires transform from those of bulk silicon to completely new spectra as the wire diameter decreases. The critical diameter for such transformation was found to be about or smaller than 100 nm.…”

Nanoscale Conductive Channels in Silicon Whiskers with Nickel Impurity

“…On the other hand, a number of size effects in Si whiskers were also established. Particularly, by reducing the diameter of the submicron whiskers to less than 500 nm, one can obtain a decrease of the lattice parameter [ 10 ] and a shift of the optical absorption edge towards higher energies [ 11 ]. The observed features of Si whiskers are associated with an absence of any defects in the crystal lattice and/or an influence of the whisker surface.…”

Photosensitive self-assembled nanoarchitectures containing surfactant-free Si nanocrystals produced by laser fragmentation in water

“…Due to the potential scientific and industrial impact, research in semiconductor nanoparticles, and in particular in silicon nanocrystals, is currently one of the most active within physics and physical chemistry [15][16][17][18][19][20][21][22][23][24]. Although self-organization or self-assembly of nanocrystalline silicon structures and/or silicon nanocrystals (Si-ncs) have been reported [20,25,26] a reliable fabrication technique capable of producing 1D and 2D assemblies with long range order remains still a challenge.…”