| 1. |
- Valenta, J., et al.
(författare)
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Active planar optical waveguide made from luminescent silicon nanocrystals
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:6, s. 955-957
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Tidskriftsartikel (refereegranskat)abstract
- We show experimentally that a layer of silicon nanocrystals, prepared by the Si-ion implantation (with the energy of 400 keV) into a synthetic silica slab and exhibiting room-temperature red photoluminescence, can serve simultaneously as a single-mode planar optical waveguide. The waveguide is shown to self-select guided transverse electric and transverse magnetic modes from the broad photoluminescence emission of the nanocrystals resulting in a substantially narrower emission spectrum for these modes. We further report on an investigation of optical gain in a sample implanted to a dose of 4x10(17) cm(-2). Despite the occurrence of strong waveguiding, results of the variable stripe length method turned out not to be able to give unambiguous evidence for optical gain.
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| 2. |
- Valenta, J., et al.
(författare)
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Photonic band-gap effects on photoluminescence of silicon nanocrystals embedded in artificial opals
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:8, s. 4471-4474
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Tidskriftsartikel (refereegranskat)abstract
- Si nanocrystals were formed in synthetic opals by Si-ion implantation and their optical properties studied using microphotoluminescence and reflection techniques. The properties of areas with high crystalline quality are compared with those of disordered regions of samples. The photoluminescence spectrum from Si nanocrystals embedded in silica spheres is narrowed by the inhibition of emission at wavelengths corresponding to the opal photonic pseudoband gap (similar to690 nm). Measurements of photoluminescence spectra from individual implanted silica spheres is also demonstrated and the number of emitting Si nanocrystals in single brightly emitting spheres is estimated to be of the order of one thousand.
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| 3. |
- Janda, Petr, et al.
(författare)
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Modified spontaneous emission of silicon nanocrystals embedded in artificial opals
- 2007
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 40:19, s. 5847-5853
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Tidskriftsartikel (refereegranskat)abstract
- Si nanocrystals (NCs) were embedded in synthetic silica opals by means of Si-ion implantation or opal impregnation with porous-Si suspensions. In both types of sample photoluminescence (PL) is strongly Bragg-reflection attenuated (up to 75%) at the frequency of the opal stop-band in a direction perpendicular to the ( 1 1 1) face of the perfect hcp opal structure. Time-resolved PL shows a rich distribution of decay rates, which contains both shorter and longer decay components compared with the ordinary stretched exponential decay of Si NCs. This effect reflects changes in the spontaneous emission rate of Si NCs due to variations in the local density of states of real opal containing defects.
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| 4. |
- Valenta, J., et al.
(författare)
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Microcavity-like leaky mode emission from a planar optical waveguide made of luminescent silicon nanocrystals
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:9, s. 5222-5225
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Tidskriftsartikel (refereegranskat)abstract
- The propagation of light emitted from silicon nanocrystals forming planar waveguides buried in SiO2 is studied both experimentally and theoretically. Experiments reveal that photoluminescence spectra detected from the sample facet mainly contains narrow (10-20 nm full-with-at-half-maximum) polarization-resolved transverse electric and transverse magnetic modes instead of the usual broad nanocrystal emission band peaked at 700-800 nm. A theoretical model developed in the framework of wave optics identifies these modes as substrate modes propagating along the waveguide boundary (not the usual modes guided inside the nanocrystal plane due to its graded index profile). This peculiar observation is the consequence of the high losses in the nanocrystalline waveguide and may occur in other dissipative waveguide structures under conditions that are discussed.
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| 5. |
- Whitlow, Harry J, et al.
(författare)
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Measurements of Si ion stopping in amorphous silicon
- 2002
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 190:1-4, s. 84-88
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Tidskriftsartikel (refereegranskat)abstract
- The stopping of Si-28 ions in polycrystalline Si foils has been measured over the energy range 0.1-3.3 MeV per nucleon. For the low energy interval (0.1-0.5 MeV per nucleon), time of flight-energy elastic recoil detection analysis method was used, whilst for the high energy region (1.2-3.3 MeV per nucleon) the energy loss in the same foil was measured using a Si p-i-n diode with the Si-28 ions directly incident on the foil following acceleration. Below the stopping maximum the results are in good agreement with literature data based on Doppler shift measurements of short nuclear lifetimes but are about 20%, smaller than the SRIM prediction. Above the stopping maximum the data are in agreement with SRIM within the limits of statistical uncertainty.
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