Comparison of optical properties in Er x Sc 2x Si 2 O 7 and Er 2x Y x Si 2 O 7 silicate and their applications (original) (raw)
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Scandium effect on the luminescence of Er-Sc silicates prepared from multi-nanolayer films
Nanoscale Research Letters, 2014
Polycrystalline Er-Sc silicates (Er x Sc 2−x Si 2 O 7 and Er x Sc 2−x SiO 5) were fabricated using multilayer nanostructured films of Er 2 O 3 /SiO 2 /Sc 2 O 3 deposited on SiO 2 /Si substrates by RF sputtering and thermal annealing at high temperature. The films were characterized by synchrotron radiation grazing incidence X-ray diffraction, cross-sectional transmission electron microscopy, energy-dispersive X-ray spectroscopy, and micro-photoluminescence measurements. The Er-Sc silicate phase Er x Sc 2−x Si 2 O 7 is the dominant film, and Er and Sc are homogeneously distributed after thermal treatment because of the excess of oxygen from SiO 2 interlayers. The Er concentration of 6.7 × 10 21 atoms/cm 3 was achieved due to the presence of Sc that dilutes the Er concentration and generates concentration quenching. During silicate formation, the erbium diffusion coefficient in the silicate phase is estimated to be 1 × 10 −15 cm 2 /s at 1,250°C. The dominant Er x Sc 2 − x Si 2 O 7 layer shows a room-temperature photoluminescence peak at 1,537 nm with the full width at half maximum (FWHM) of 1.6 nm. The peak emission shift compared to that of the Y-Er silicate (where Y and Er have almost the same ionic radii) and the narrow FWHM are due to the small ionic radii of Sc 3+ which enhance the crystal field strength affecting the optical properties of Er 3+ ions located at the well-defined lattice sites of the Sc silicate. The Er-Sc silicate with narrow FWHM opens a promising way to prepare photonic crystal light-emitting devices.
Optical and structural properties of SiO2 co-doped with Si-nc and Er3+ ions
Proceedings of SPIE - The International Society for Optical Engineering, 2010
We present a study on erbium-doped silicon rich silicon oxide (SRSO:Er) thin films grown by the magnetron cosputtering of a three confocal cathodes according to the deposition temperature and the annealing treatment. It is shown that several parameters such as the stoichiometry SiO x , the Erbium content and the fraction of agglomerated Silicon are strongly influenced by the deposition temperature. Especially, an increase of the fraction of agglomerated-Si concomitant to a reduction of the erbium content is observed when the deposition temperature is raised. These structural differences have some repercussions on the optical properties that lead to better performances for high-temperature deposited material. It is illustrated by the Er-PL efficiency that is higher for 500°C-deposited than for RT-deposited sample at all annealing temperatures. Finally an investigation of the different emitting centres within the films is performed with a cathodoluminescence technique to highlight the emission of optically-active defect centers in the matrix. It is shown that some oxygen vacancies, namely Silicon-Oxygen Deficient Centers, have a strong contribution around 450-500 nm and are suspected to contribute to the energy transfer towards Er 3+ ions.
Efficient Luminescence and Energy Transfer in Erbium Silicate Thin Films
Advanced Materials, 2007
Currently, electrical interconnections based on metal lines represent the most important limitation on the performances of silicon-based microelectronic devices. The parasitic capacities generated at the metal/insulator/metal capacitors present in the complex multilevel metallization schemes actually used, the intrinsic resistivity of the metal lines, and the contact resistance at the metal/metal interfaces constitute the main contributions to the delay in the signal propagation. Recently, a reduction of the delay times was achieved by replacing the traditional metallization schemes based on Al and SiO 2 with new materials, such as copper-based alloys and low-dielectricconstant insulating layers, but as soon as the minimum feature size of the devices will be further reduced, the delay resulting from metal interconnections will again represent an unacceptable bottleneck for device performances. A definitive solution to this problem could be the use of optical interconnections for the transfer of information inside a chip or for chip-to-chip communications. To develop this strategy, siliconcompatible materials and devices able to generate, guide, amplify, switch, modulate, and detect light are needed. Recent major breakthroughs in this field have been the observation of optical gain in Si nanocrystals, the development of a Si Raman laser, the realization of a high-speed Si electro-optic modulator, and the observation of electroluminescence from ultrapure Si diodes and Si nanocrystal field-effect transistors. A primary requirement for the materials proposed for the above applications is compatibility with current Si technology. However, because Si is intrinsically unable to efficiently emit light, owing to its indirect bandgap, it is evident that the main limitation to the approach described above is the lack of an efficient silicon-based light source. Among the efforts of the scientific community to efficiently produce photons from silicon, the introduction of light-emitting impurities, such as erbium ions, has a leading role. A relevant advantage of this approach is that standard silicon technology can be used to introduce erbium as a dopant and to process the material. Furthermore, Er ions emit at 1.54 lm, which is a strategic wavelength for telecommunication because it corresponds to a minimum in the loss spectrum of the silica optical fibers. Incorporation of Er in crystalline silicon (c-Si) emerged as the first promising method to turn silicon into a luminescent material, but doping concentration was limited (ca. 1 × 10 18 cm -3 ) by the low solid solubility of Er. A co-implantation of Er and O allowed to limit Er segregation and precipitation, owing to the formation of Er-O complexes. However, at room temperature a relatively low luminescence efficiency was obtained as a result of the strong nonradiative processes competing with the radiative Er de-excitation in c-Si. More recently, it was shown that by using a SiO 2 matrix containing Er-doped Si nanoclusters, an intense room-temperature Er luminescence can be obtained. Indeed, it has been demonstrated that Si nanoclusters in presence of Er act as efficient sensitizers for the rare earth owing to the effective Er excitation cross section, which is more than two orders of magnitude higher compared with the Er resonant absorption of a photon. Optical gain from waveguides based on Er-doped Si nanoclusters has been also reported, and lightemitting devices have been fabricated. However, the optical gain that can be obtained from this system is critically dependent on its Si content, and it is limited by the confined carrier absorption resulting from the presence of Si nanoclusters. Even if gain can prevail over absorption through a careful balance of Er and Si concentrations, absorption could represent a limit for obtaining high gain values from Er-doped Si nanoclusters.
Unexpected behavior of the 1.54μm luminescence in Er-doped silica films
Journal of Non-Crystalline Solids, 2014
Materials such as Er:glass are still of great interest in optical communication technology for their applications in photonic devices operating at the standard telecommunication wavelengths. The 1.54 μm emission properties of the Er 3+ ions embedded in glassy systems depend on several factors, as for instance the synthesis technique and the thermal history of the material. A photoluminescence investigation, made on Er:SiO 2 thin films deposited by PVD for a wide range of different Er concentration and subsequently annealed in the range 50-1200°C (with 50°C step), was done to investigate in which way both Er concentration and thermal annealing influence the 1.54 μm emission performance of the Er:SiO 2 glass system. For low Er concentration, we evidenced an unexpected 1.54 μm activity also after annealing at temperatures much lower than the usual ones. We suspect that this behavior could be related to the medium/long-range order around the Er 3+ ions, as a possible consequence of local silica polymorphs formation.
Photoluminescence characterization of Er3+ -implanted silica thin films containing Si nanocrystals
Rare-Earth-Doped Materials and Devices IV, 2000
Si nanocrystals (nc-Si) embedded in silica have recently attracted a lot of attention as a potential optoelectronic material due to their light emission at -1 .7 eV. Er is attractive because its 1 .53 im emission coincides with the low attenuation region of silica optical fibers. In this paper, we report the experimental investigation of energy transfer between nc-Si and Er in ion implanted material which may relax requirements on the Er pump source and lead to broad-band pumped optical devices.
Materials Science and Engineering: B, 2000
It is well-known that the sharp luminescence emission at 1.54 mm from erbium-doped silicon has set off a great interest for this material in view of its applications in the third window of optical telecommunications. It is also known that the erbium luminescence is very poor in the absence of impurities like oxygen, carbon and nitrogen, but in spite of the large amount of research work devoted to this material, it is not yet completely clear what is the local structure of the optically active Er centre in oxygen-doped Er-Si alloys. The aim of this paper is to present and discuss the results of the analysis of the EXAFS spectra of two sets of Er-doped silicon samples, of which one was obtained by erbium and oxygen co-implantation and the other was grown by LPE (liquid phase epitaxy). The EXAFS spectra of these samples were satisfactorily fitted by assuming that Er sits in three different configurations, depending on the presence or the absence of oxygen and dislocations in the epi-layer. The relevance of these results in terms of optical and electrical activity of erbium is discussed in details.
Journal of Non-Crystalline Solids, 2014
Er and Er/Yb doped photosensitive multicomponent silicate glasses with composition of 60SiO 2-10GeO 2-10B 2 O 3-20Na 2 O (in wt.%) were prepared and characterized in terms of absorption cross-section (σ a), fluorescence lifetime (τ m) and concentration quenching effect. The solubility of rare earth ions in this glass is much higher (to 2 wt.%) than that of conventional silicate glasses, with corresponding lifetime and quantum efficiency of τ m = 7.5 ms and η = 50%, respectively. Glasses with different Er/Yb ratios were also made to investigate the effects of Er/Yb ratios on energy transfer efficiency. A ratio of Er/Yb = 0.4 showed higher absorption cross-section compared to 0.2 and 0.6. The lifetime for all samples decreased with the addition of Yb 2 O 3. We also report on the 1.5 μm emission line broadening of Er 3+ ion emission in these glasses. The emission of full width at half maximum shifted from 25.7 nm to 48.2 nm and the increased line width was found to correlate to an increase in Er 3+ concentration in such a multicomponent glass. The studied glass with multifunctional properties is proved to be a very good candidate for application in integrated optics.
Structural and optical properties of Er3+ doped SiO2–Al2O3–GeO2 compounds prepared by a simple route
Materials Science and Engineering: B, 2015
Samples of (1 − x)[0.70SiO 2 + 0.30Al 2 O 3 ] + xGeO 2 compositions, containing x = 0.05, 0.10, 0.20, 0.30, 0.40 and 0.50, and doped with 1 mol% of Er 3+ , were prepared by a mixed route (sol-gel process and Pechini method). Transparent gels were synthesized and homogeneous powders were obtained by heat treatments from 800 • C to 1050 • C. The final powders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and high-resolution transmission electron microscopy. The optical properties were studied by photoluminescence measurements in the infrared region, and the average lifetime of the metastable state 4 I 13/2 of Er 3+ ions and the full-width at half maximum (FWHM) were determined. A silica-rich amorphous phase and nanocrystallites with orthorhombic structure of Al 6 Ge 2 O 13 phase were obtained. The samples present a broad emission centered at around 1532 nm under excitation at 977 nm, with a FWHM of 53 nm and a lifetime of 5.6 ms. The synthesized compounds by an easy chemical procedure are potentially applicable in integrated optical systems.
Erbium doped silicon as an optoelectronic semiconductor material
1994
In this thesis, the materials aspects of erbium-doped silicon (Si:Er) are studied to maximize Si:Er luminescence intensity and to improve Si:Er performance as an optoelectronic semiconductor material. Studies of erbium (Er) and silicon (Si) reactivity, erbium diffusion and solubility in silicon, Si:Er heat treatment processing with oxygen and fluorine co-implantation and the mechanism of Si:Er light emission have been carried out to define optimum processing conditions and to understand the nature of optically active centers in Si:Er. In the erbium and silicon reactivity studies, a ternary phase diagram of Er-Si-O was determined. ErSi 2 _x(X = .3) was found to be the most stable erbium silicide formed on single crystal silicon, and it could be oxidized in the presence of oxygen (02). These findings confirm the results that erbium precipitates as ErSi2_(x = .3) in silicon and erbium clusters with oxygen to form complexes in Si:Er with oxygen co-implantation. Luminescence studies on various erbium compounds established a unique spectrum for Si:Er, which can be used to fingerprint products of Si:Er processing. The diffusivity and solubility of Er in Si are determined based on the analysis of changes in implanted Er SIMS profiles of Si:Er after high temperature annealing (1150-1300 0 C). Er is a slow diffuser with moderate solubility in Si. The diffusivity of Er in Si D(Er) is 5 x 10-11 cm 2 /s at 1200°C with a migration energy of-4.6eV, at a rate similar to Ge in Si. The equilibrium solid solubility of Er in Si [Er], is , 10 1 l 6 atoms/cm 3 between 1150-1300 0 C, similar to S in Si. The low Er diffusivity in Si enables metastable concentrations of Er to be incorporated into Si at levels far exceeding the equilibrium solid solubility of 10 16 atoms/cm 3. Furthermore, the low diffusivity and high oxidation tendency make Si:Er process compatible with existing Si fablines, since cross contamination during heat treatment is minimized. Post-implantation annealing and ligand enhancement are essential to achieve luminescence in Si:Er. The heat treatment process of Si:Er and the impact of oxygen (O) and fluorine (F) ligands have been studied. The Si:Er heat treatment process is determined by three internal processes in Si:Er: (1) implantation damage anneal; (2) I would like to thank my advisor Professor L.C. Kimerling for his insights and guidance on directing my thesis research and as a personal role model for hardworking and effective communication. I feel very fortunate to have been his first Ph.D student at MIT. I would also like to thank other members of my thesis committee Professors Tuller and Bawendi for their advise and support. I am indebted to Dr. Jurgen Michel for many discussions about the project. His friendship and his help on photoluminescence measurements were most appreciated. I am also grateful to Visiting Professor Hajime Kitagawa from Fukuoka Institute of Technology, Japan, who worked with me at the early stage of this project when we were setting up the lab. A special thank to Professor Scott Dunham at Boston University, who had helped me to start on the Si:Er process simulation and generously provide free access to the PEPPER and PROFILE software. I want to acknowledge Dr. Dale Jacobson and Dr. John Poate at AT&T Bell Laboratory for supplying the implanted materials. Many other people at MIT had helped me throughout the course of this thesis research. In particular, I want to thank John Martin at the MIT Surface Analytical Lab, who helped me in performing SIMS measurements. I would also like to acknowledge the past and present members of our Silicon Microphotonics research group