Visible photoluminescence in Si+-implanted silica glass

Abstract

We have investigated visible photoluminescence excited by Ar-ion laser (488 nm, 2.54 eV) at room temperature from Si+-implanted silica glass, as-implanted and after subsequent annealing in vacuum. We found two visible luminescence bands: one peaked around 2.0 eV, observed in as-implanted specimens and annealed completely after heating to about 600 °C, the other peaked around 1.7 eV observed only after heating to about 1100 °C, the temperature at which Si segregates from SiOx. It was found that the 2.0 eV band anneals parallel to the E′ centers, as detected by electron spin resonance studies. It was also found that Raman lines around 520 cm−1, due to Si—Si bonds, grow and that interference patterns are induced by annealing Si+-implanted silica glass. Based on these studies, we ascribe the 2.0 eV band to the electron-hole recombination in Si-rich SiO2 and the 1.7 eV band to the electron-hole recombination in the interface between the Si nanocrystal and the SiO2 formed by segregation of crystalline Si from SiOx.

Luminescence efficiency measurements of silicon nanoclusters

“…There has been much debate over the nature of the luminescence mechanism in this material and contradictory reports of its optical properties, but there is a growing consensus that, in common with porous silicon, quantum confinement of excitons within the nanoclusters plays a significant role. [7][8][9][10] Previous work by this group has addressed the nature of the luminescence mechanism and has indicated the presence of two distinct processes: radiative recombination of confined excitons within the silicon nanoclusters and defect luminescence from the surrounding matrix. 7,8 A single unique mechanism does not provide a good enough explanation of the luminescence properties of nanoscale silicon.…”

The origin of photoluminescence from thin films of silicon-rich silica

“…Some groups have reported bright, broadband emission from asgrown thin films of silicon-rich silica, 17 while other groups see nothing until their samples are annealed. 27 While some reports show a redshift of peak luminescence wavelength with increasing annealing temperature, 13,24,27 others exhibit a fixed spectral distribution. 14,28 Similarly, it is not clear whether temperature quenching of luminescence is significant in this material: some groups show a strong dependence of luminescence intensity on sample temperature, 28 others see no change on cooling samples to 70 K. 24 As yet there is no model which adequately explains the wide range of experimental observations: it seems possible that more than one mechanism contributes to luminescence.…”

“…It may be that several mechanisms operate at once or that different processes are favored by different growth conditions and/or postprocessing. Recently, a few groups, notably Shimizu-Iwayama and co-workers, 13,14 Fischer et al, 17 and to some extent Komoda et al 12 have begun to make progress in identifying mechanisms. Studying silicon-implanted silica, Shimizu-Iwayama identified two bands in the photoluminescence spectrum, one around 2.2 eV and another at 1.7 eV.…”

“…Recent results have demonstrated broadband light emission from the blue to near infrared from material containing silicon aggregates of varying sizes. [12][13][14][15][16][17][18] However, there is considerable uncertainty about the nature of the luminescence mechanism from silicon-rich silica. A number of possibilities present themselves: radiative recombination of confined excitons within silicon clusters ͑''quantum dots''͒, 23 defect luminescence, 24 interfacial effects at cluster surfaces, 25 and luminescence from novel siloxene molecules.…”

“…Although luminescence was reported in this material some time ago, 11 it is only recently that its optical properties have begun to be thoroughly studied. A number of techniques have been employed in its production, including implantation of silicon into silica, [12][13][14] implantation of oxygen into silicon, 15,16 plasma enhanced chemical vapor deposition ͑PECVD͒, 17,18 low-pressure chemical vapor deposition ͑LPCVD͒, 19,20 and co-sputtering of silicon and oxygen. 21,22 X-ray diffraction and transmission electron microscopy ͑TEM͒ studies have confirmed the presence of clusters of silicon atoms in the SiO 2 matrix.…”