The effect of the temperature ranging from cryogenics to room temperature were investigated on the formation of the optically-active point defect called the G-centre. The G- centre as an emissive ...point defect gained a lot of attention recently due to its sharp zero phonon luminescence peak at a wavelength of 1.28 μm (0.97 eV) with the evidence of lasing occurred in the structure. The emission of the G-centre is attributed to the carbon substitutional-carbon interstitial (CsCi) complex which interacts with silicon interstitials during the damage event. This complex is generated by implantation of carbon and followed by proton irradiation. Prior to the carbon implantation, two of the samples were pre-amorphised by germanium. Photoluminescence (PL) measurements were carried out at temperature ranging from 80 K up to room temperature to observe the intensity of the main peaks. The results confirm that the main peaks of point-defect centre in all of the samples including the G-centre suffer from the temperature quenching. However, the peak intensity for some of the wavelength especially the ones with high FWHM, do perform better at high temperature. The temperature quenching phenomena observed in the point-defect technique is the main problem that needs to be addressed and solved before realizing the method in the all silicon photonic system.
We report waveguides in Ni-doped Li sub(2)O-Ga sub(2)O sub(3)-SiO sub(2 ) (Ni:LGS) glass and glass-ceramic (GC) fabricated with a femtosecond (fs) laser with repetition rate of 1 kHz. When the glass ...is annealed to form a GC, the waveguides are erased. However, in the GC the waveguides are not erased by annealing. In Ni:LGS GC a 415 nm absorption band was created by fs laser waveguide writing due to the creation of Ni nanoparticles with an estimated diameter of a few nm. Raman and photoluminescence spectra of the bulk and waveguide structures were indistinguishable; however, fluorescence decay profiles indicated more long lifetime components in the waveguide compared to the bulk.
Photoluminescence in the 1.2–1.35
μm range has been observed in silicon substrates incorporating thulium in the trivalent Tm
3+ state and co-doped with boron. The results showed eight sharp lines at ...1211.5, 1231.0, 1250.8, 1269.3, 1283.8, 1290.6, 1311.3 and 1326.0
nm, corresponding to known internal Tm
3+ transitions in the manifold from the
3H
5 to the
3H
6 ground states. The luminescence was strongly dependent on the sample fabrication processes. In this paper we will discuss the influence of Tm implantation parameters and post-implant annealing conditions on the photoluminescence response of silicon doped with Tm
3+.
Development programmes for pastoralist communities in sub-Saharan Africa have concentrated on livestock development as a means to improve economic, nutritional and other standards of living. This ...paper looks at the outcomes of two decades of development inputs (1960-1980) among Maasai communities in socialist Tanzania and capitalist Kenya. Despite major differences in national economies, infrastructures and inputs, there are few significant differences in measures of livestock production, wealth holdings, dietary energy intake and child nutritional status for Tanzanian and Kenyan Maasai. Where data exist for comparison it is clear that food production and consumption show little change from the 1960s and earlier. Reasons for the failure of development inputs and the apparent lack of change in Maasai pastoralist ecology are examined, as are the implications for currently planned development inputs in Tanzania Maasailand. Results are discussed in the wider context of sub-Saharan Africa.
Stability of nano-scaled Ta/Ti multilayers upon argon ion irradiation Milosavljević, M.; Milinović, V.; Peruško, D. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
10/2011, Letnik:
269, Številka:
19
Journal Article
Recenzirano
► The effects of argon ion irradiation on Ta/Ti multilayers were investigated. ► Despite of relatively heavy ion irradiation, Ta and Ti layers remain unmixed. ► Individual nanocrystalline layers keep ...the same level of interface planarity. ► Such behavior is assigned to dynamic demixing due to chemical driving forces. ► The results can be interesting towards developing radiation tolerant materials.
The effects of argon ion irradiation on structural changes in Ta/Ti multilayers deposited on Si wafers were investigated. The starting structures consisted of sputter deposited 10 alternate Ta (∼23
nm) and Ti (∼17
nm) layers of a total thickness ∼200
nm. They were irradiated at room temperature with 200
keV Ar
+, to the fluences from 5
×
10
15 to 2
×
10
16
ions/cm
2. The projected ion range was around mid-depth of the multilayered structure, and maximum displacements per atom ∼130. It was found that, despite of the relatively heavy ion irradiation, individual nanocrystalline Ta and Ti layers remain unmixed, keeping the same level of interface planarity. The changes observed in the mostly affected region are increase in lateral dimensions of crystal grains in individual layers, and incorporation of bubbles and defects that cause some stretching of the crystal lattice. Absence of interlayer mixing is assigned to Ta–Ti immiscibility (reaction enthalpy Δ
H
f
=
+2
kJ/mol). It is estimated that up to ∼5
at.% interface mixing induced directly by collision cascades could be compensated by dynamic demixing due to chemical driving forces in the temperature relaxation regime. The results can be interesting towards developing radiation tolerant materials based on multilayered structures.
We report here on the synthesis of semiconducting amorphous FeSi2 layers by co-sputter deposition of Fe and Si on silicon (100) wafers. The layers were grown to a thickness of 300-400 nm, at various ...substrate temperatures. Structural characterisation has shown that the deposited layers have the FeSi2 stoichiometry and are fully amorphous up to a deposition temperature of 200 DGC. Optical absorption measurements have demonstrated that the amorphous FeSi2 layers have semiconducting properties, with a direct band gap of 0.89-0.90 eV at room temperature (RT). In order to relax the amorphous structure, some samples were irradiated with 200 keV Ar ions. It was found that both an increased deposition temperature and/or ion irradiation induce a higher photo-absorption, which was attributed to establishing a medium range order in the amorphous phase. The applied fabrication routine can be highly efficient for potential applications of this material in large area electronics and for production of solar cells.
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