Impact of europium concentration on thermal and absorption features of amorphous tellurite media

Improving the structural and optical properties of tellurite glasses via optimized doping of rare earth ions is an outstanding issue in materials science. Tellurite glasses doped with trivalent europium (Eu3+) are successfully prepared using conventional melt quenching technique. Glasses with chemical composition of (80-x)TeO2-10PbO-10ZnO-(x)Eu2O3 where 0 ≤ x ≤ 2.0 mol% are obtained. The influence of Eu3+ ions concentration on the thermal and absorption properties of the synthesized glasses is investigated using Differential Thermal Analyzer (DTA) and UV-VIS Spectroscopy. DTA curves in the temperature range of 50-1000 °C at a heating rate of 10 °C/min are used to determine the temperature of glass transition, crystallization, melting and in turn the thermal stability. DTA revealed that the increase in the Eu3+ contents improved the thermal stability. This observation is attributed to the alteration of the glass network structure via the creation of non-bridging oxygen. The room temperature absorption spectra recorded in the spectral region of 200 – 2000 nm exhibited three absorption peaks corresponding to 7F0 → 5D0, 7F0 → 5D1 and 7F0 → 5D2 transitions. The absorption intensity is found to be enhanced up to certain concentration of Eu3+ ions and then quenched. This is ascribed to the change in glass network structure and formation of defects through the cleavage of weak bonds and reduction in covalence states

Spectral characteristics of antimony-phosphate glass

Determining the stable optimized compositions of the binary and ternary phases of antimony-phosphate glasses is the key issue. We prepare four series of glasses of the form (100- x)Sb2O3-xP2O5, where x = 30, 40, 50, 60 and 70 mol%, (95-x)Sb2O3-xP2O5-5MgO, where x = 60, 45, 40, 35, 30 and 25 mol%, (85-x)Sb2O3-xP2O5-15MgO, where x = 60, 45, 40, 35, 30 and 25 mol% and (75-x)Sb2O3-xP2O5-25MgO, where x = 60, 45, 40, 35, 30 and 25 mol% via conventional melt quenching method. Structural and optical properties of these glasses are determined through FTIR, UV-Vis and PL measurements. The XRD patterns confirm the amorphous nature of samples. The FTIR spectra of all prepared glass series recorded in the spectral ranges of 400 to 4000 cm-1 demonstrates the presence of asymmetric stretching vibrations of (PO3)2, Sb2O3 doubly degenerate stretching vibrations, stretching vibration of P–O–Sb linkages, vibration modes of SbO3 of the valentinite and vibration modes of SbO3 of the valentinite. The UV-Vis absorption spectra in the wavelength range of 200-2000 nm exhibit a broad transparency range with short wavelength absorption edge located at around 380 nm. A small shift of the absorption edge due to the change in glass composition is evidenced. The room temperature emission spectra under four different excitation wavelengths such as 300, 380, 550 and 780 nm display single sharp second harmonic emission peak at half wavelength and double frequency of the excitation wavelength. Glasses reveal low durability against humidity at higher P2O5 concentration exceeding 65 mol%. Furthermore, initiation of glass formation begins when Sb2O3 concentration is found to be less than or equal to 40 mol% for the binary system and 60 mol% for the ternary one. These promising features of the optical properties are highly useful for widespread photonic applications

Effect of tungsten on physical and optical properties of niobatetellurite glasses

In the present work, three optically transparent tungsten niobate tellurite glasses with compositions of (90-x)TeO2-10Nb2O5-xWO3 (x = 0, 6, 12 mol%) were synthesized by conventional melt quenching technique. For all these three glass samples, the structural and the compositional dependence of different physical parameters such as density, molar volume and ionic packing density have been analyzed. It been observed that the amorphous nature of the samples has been confirm by X-ray diffraction analysis. The physical properties of the glasses were evaluated and the change in density ( ), molar volume ( ) and ionic packing density ( ) in these glasses indicates the effect of WO3 different content registered on the glasses structure. The highest refractive indexes value 2.171 at 632.8 nm was measured for 78TeO2–10Nb2O5–12WO3 glass. It is found that the addition of WO3 concentration to TeO2-Nb2O5 glass system increase the value of density, molar volume as well as ionic packing density. The refractive index value of the glass increase with tendency for small optical energy band gap

Silver nanoparticles assisted spectral features enhancement of Samarium-Zinc-Tellurite glass

Achieving the enhanced optical properties of rare earth doped inorganic glasses by embedding metallic nanoparticles (NPs) is ever-demanding in photonics. Optimized doping of NPs and subsequent thorough characterizations for improved absorption and emission are the key issues for lasing glasses. We inspect the influence of silver (Ag) NPs inclusion on the optical properties of Sm3+ doped zinc-sodium tellurite glasses having composition 65TeO2-25ZnO-10Na2O- (0.15 gram)Sm2O3-(y)AgCl, where y = 0, 0.03, 0.075, 0.12 and 0.18 gram (in excess). Glass samples are prepared using melt quenching technique and characterized via ultraviolet visible near infrared (UV-Vis-NIR) absorption and photoluminescence (PL) spectroscopy. The presence of NPs is verified from TEM images and the amorphous nature is confirmed from XRD pattern. The UV-Vis- NIR spectra revealing six absorption peaks centered at 472, 943, 1089, 1237, 1392, and 1491 nm are assigned to 6H5/2→4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2 transitions, respectively. PL spectra exhibit two emission bands located at 599 nm (4G5/2→6H7/2) and 643 nm (6H9/2). The observed enhancement in PL intensity is attributed to the highly localized electric field of Ag NPs positioned in the vicinity of Sm3+ ion. The mechanism of enhancement is identified, analyzed, and understood. The admirable features of our results are highly beneficial for solidstate laser and optical device fabrication

Sm3+:Ag NPs assisted modification in absorption features of magnesium tellurite glass

Metallic nanoparticles (NPs) assisted enhancements in absorption and emission cross-section of tellurite glass is the present challenge. The influences of samarium (Sm3+) ions and silver (Ag) NPs ratio on physical and optical absorption properties of melt quench synthesized magnesium tellurite glasses are reported. XRD patterns verify the amorphous nature of glasses. Glass density, molar volume and ionic packing fraction are discerned to be in the range of 4.92-5.0 g cm-3, 29.82-30.26 cm3 mol-1 and 0.452-0.446, respectively. Moderate reduction potential of tellurite glass converted Ag1+ to Ag0 via single step process and NPs are formed. TEM image manifest the existence of NPs of average diameter ~16.94 nm having Gaussian size distribution. The significant changes in structural properties in the presence of Ag NPs are discussed in terms of TeO4 tetrahedra distortion and network depolymerization process. The Sm3+:Ag NPs dependent variation in physical properties are ascribed to the alteration in the number of bridging oxygen to non bridging (NB) one. Enhancement in absorption intensity due to the local field effects of Ag NPs is attributed to the changes in Sm-O bond strength. Optical energy band gap (2.81-3.18 eV) and Urbach energy (0.18-0.24 eV) are found increase and decrease, respectively with the increase of Sm3+:Ag NPs up to 1.33 then quenches and enhances, respectively thereafter which are related to the changes in cross-link and NBO numbers. The FTIR spectra reveal modification in network structures evidenced from vibrational wave-number shifts of TeO4 and TeO3 structural units. The observed notable increase in HOH vibration mode suggests its helpfulness in promoting the absorption of water and light. It is asserted that the physical, optical and structural properties of magnesium tellurite glass can be tuned by controlling Sm3+:Ag NPs

Modified absorption features of Titania-Erbium incorporated plasmonic tellurite glass system

Achieving efficient lasing glass materials with enhanced absorption and emission cross-section by reducing the Rare Earth (RE) concentration quenching is a challenging issue. Metal nanoparticles (NPs) together with RE ions in the glass matrix are thought as a suitable alternative to overcome the limitations of concentration quenching and weak absorption of inorganic glasses. We prepare a series of Titania-Erbium doped Tellurite glass system with the form (69-x)TeO2-20ZnO-10Na2O-1Er2O3-(x)TiO2, where 0 . x. 1.0 mol% via melt-quenching method with optimum erbium contents and varying TiO2 NPs concentrations. The NPs concentration dependent modifications in the absorption characteristics are scrutinized. Glasses are characterized via UV-Vis-NIR and XRD measurements. XRD pattern verifies the amorphous nature of prepared samples. The incorporation of TiO2 NPs is demonstrated to enhance the absorption intensity significantly. This augmentation is attributed to the effect of Surface Plasmon Resonance (SPR) mediated strong local electric field that is swallowed by neighboring Er3+ ions. The observed modification in optical energy band gap and Urbach energy are ascribed to the strong electric field around NPs that interact with the ligand of glass network to transform weak bond into defects. This observation is useful for the development of plasmonic nanoglass materials applicable for photonic devices

Improved absorbance of holmium activated magnesium-zinc-sulfophosphate glass

Constant efforts are dedicated to overcome the limitations of phosphate based glass system, where sulfophosphate glasses (SPGs) played a key role. Rare earth ions (REIs) doped magnesium zinc SPG (MZSPG) systems are technologically prospective due to their several unique attributes. Construction of integrated light amplifier and solid state laser needs the maximum gain within small component dimensions. Thus, Ho3+ ions doped SPGs are believed to meet this demand. Ho3+ ions having sharp optical absorption peaks in the spectral range of 200–900 nm is useful for diversified applications. Conversely, SPGs comprising of oxides of sulphur, phosphorous and at least one other component with SO42- ions contents lower than PO43- with low melting temperature makes them a distinctive class of technologically potential disordered system. In this view, modification of Ho3+ ions absorbance inside SPGs network is challenging. To achieve this goal, following melt-quenching route we prepared a series of Ho3+-doped MZSPG system of composition (60-x)P2O5-(20)ZnSO4-(20)MgO–(x)Ho2O3,where x = 0.0, 0.5, 1.0, 1.5 2.0, and 2.5 mol%. The influence of Ho2O3 concentration on the density, refractive index, and optical absorption properties of the synthesized glass system is examined. The density and refractive index is found to increase with increasing Ho2O3 concentration. The absorption spectra obtained using Shimadzu UV-3101PC spectrometer revealed nine prominent peaks centered at 387, 418, 450, 484, 538, 642, 1148 and 1945 nm. The glass absorbance is enhanced with increasing Ho3+ contents. Optical band gap energy is found to range from 3.847 to 3.901 eV. TheUrbach energy reduced from 0.257 to 0.191 eV with increasing Ho3+ contents. In-depth investigations on the structural and optical properties of MZSPG system are underway to achieve the milestones set for photonic devices

Modified absorption features of Titania-Erbium incorporated plasmonic tellurite glass system

Achieving efficient lasing glass materials with enhanced absorption and emission cross-section by reducing the Rare Earth (RE) concentration quenching is a challenging issue. Metal nanoparticles (NPs) together with RE ions in the glass matrix are thought as a suitable alternative to overcome the limitations of concentration quenching and weak absorption of inorganic glasses. We prepare a series of Titania-Erbium doped Tellurite glass system with the form (69-x)TeO2-20ZnO-10Na2O-1Er2O3-(x)TiO2, where 0 . x. 1.0 mol% via melt-quenching method with optimum erbium contents and varying TiO2 NPs concentrations. The NPs concentration dependent modifications in the absorption characteristics are scrutinized. Glasses are characterized via UV-Vis-NIR and XRD measurements. XRD pattern verifies the amorphous nature of prepared samples. The incorporation of TiO2 NPs is demonstrated to enhance the absorption intensity significantly. This augmentation is attributed to the effect of Surface Plasmon Resonance (SPR) mediated strong local electric field that is swallowed by neighboring Er3+ ions. The observed modification in optical energy band gap and Urbach energy are ascribed to the strong electric field around NPs that interact with the ligand of glass network to transform weak bond into defects. This observation is useful for the development of plasmonic nanoglass materials applicable for photonic devices

LIGHT EMITTING GERMANIUM AND SILICON NANOISLANDS GROWN BY RF MAGNETRON SPUTTERING

The role of annealing temperature on the structural and optical properties of Ge and Si nanoislands deposited on Si(100) grown by radio frequency magnetron sputtering technique are studied. Atomic force microscopy confirmed the formation of Si and Ge nanoislands with estimated sizes lower than 100 nm and 45 nm respectively. The room temperature photoluminescence spectra for Si revealed an emission peak at 2.53 eV which is attributed to the formation of Si nanoislands whereas the observed strong luminescence peak at 3.22 eV for Ge nanoislands is attributed to the quantum size effect. A shift in the PL peak is observed upon annealing which is due to effect of quantum confinement and surface passivation by oxygen. The thermal annealing at 600 0 C is found to play an important role in controlling the shape, number density, root mean square roughness and the energy shift of the luminescence band for both Si and Ge nanoislands. The influence of annealing on growth morphology for Ge nanoislands is appeared to be stronger than Si. The growth mechanism and the luminescence is analyzed and compared with other observations

Fabrication parameters dependent morphology variation of silicon thin film

Achieving two dimensional quantum structure of silicon with welldefined tuneable morphology is an outstanding issue. We present the preliminary results on fabrication parameters dependent silicon thin film production using VHF-PECVD method. Five samples are prepared on Si(100) substrate with gold (Au) catalyst by adjusting different parameters such as deposition time, temperature and the flow of precursor gas. The samples morphology are analysed using FESEM. The results reveal that the silicon thin film appear to be smooth and crystal-like after an enormous amount of hydrogen is inserted together with the precursor gas (silane) during the deposition process. More interestingly, the films exhibit silicon nanowires as the deposition time is increased up to 1 hour. This morphological transformation is attributed to the vapour-liquid-solid (VLS) mechanism related to the deposition process. Our results may contribute towards the development of nanosilicon based optoelectronics