SiO2 Samples Research Articles

Fiber-based modulated optical reflectance configuration allowing for offset pump and probe beams.

A new fiber-based modulated optical reflectance configuration is developed in this work. The technique maintains the fiber-based heating laser (pump) and detection laser (probe) in close proximity at a fixed separation distance in a ceramic ferrule. The pump beam periodically heats the sample inducing thermal waves into the sample. The probe beam measures the temperature response at a known distance from the pump beam over a range of heating modulation frequencies. The thermal diffusivity of the sample may be calculated from the phase response between the input heat flux and the temperature response of a sample having a reflective surface. The unique measurement configuration is ideal for in situ measurements and has many advantages for laboratory-based systems. The design and development of the system are reported along with theoretical justification for the experimental design. The thermal diffusivities of Ge and SiC are measured and found to be within 10% of reported literature values. The diffusivity for SiO2 is measured with a relative difference of approximately 100% from the literature value when the ferrule is in contact with the sample. An additional measurement was made on the SiO2 sample with the ferrule not in contact resulting in a difference of less than 2% from the literature value. The difference in the SiO2 measurement when the ferrule is in contact with the sample is likely due to a parallel heat transfer path through the dual-fiber ferrule assembly.

Effect of Different Acids and Solvents on Optical Properties of SiO2 Nanoparticles Prepared by the Sol-Gel Process

SiO2 nanoparticles are prepared via a simple solgel method to provide a basic understanding of the effect of different acids, acetic acid [CH3COOH], hydrochloric acid (HCl), sulfuric acid (H2SO4) and oleic acid [C18H34O2] and solvents dimethylformamide and formamide on the morphological and optical properties. The resulting SiO2 nanoparticle were characterized by photoluminescence spectrophotometry (PL) for the study of optical properties, Transmission electron microscopy (TEM) to determine particle size and Fourier transform infrared spectroscopy (FTIR) for identification of materials and impurities. SiO2 formed with formamide and HCl shows high crystallinity and transperancy in the material. PL spectra reveal that SiO2 nanoparticles show absorbance in the UV region. For each solvent, the PL emission intensity of the SiO2 sample prepared with acid was reduced which shows the formation of well-defined lattice sites and decrease of deffects. The PL intensity of SiO2 prepared with dimethyl-formamide to acetic-acid (SD1) and SiO2 prepared with formamide to acetic-acid (SF1) samples increased. The particle size is confirmed by TEM which was indicative of the successful synthesis of SiO2 nanoparticles in spherical shape. The estimated particle size is in the range of 2-4 nm. The chemical changes were observed from the FTIR results. Strong and broad bands appeared at 3459 cm1-3458 cm−1 and 1640 cm−1-1638 cm−1 corresponding to the bending vibrations of -OH groups and carbon impurity atoms. The peaks that appeared at 989 cm−1-801 cm1 and at 966 cm-1-802 cm1 show the bending vibrations of Si-O-Si and Si-OH bonds in prepared samples.

Observation of blue persistent luminescence in amorphous silica annealed by carbon

Intense blue persistent luminescence (PersL) with sufficiently long duration time was firstly observed in SiO2 particles after calcination with carbon. In indicates that the intense PersL of the optimal SiO2 sample calcinated with carbon (1:2) at 600°C can be recorded for about 1h (0.32mcd/m2) and is actually visible for even more than 3h by the dark-adapted vision in darkness. It reveals that the defects formatted during the calcination with carbon should be associated with oxygen vacancies and they play very important roles as emitters and traps, contributing to the PersL. The depth of the dominant traps in the optimal SiO2 sample is calculated to be about 0.71eV, which is in a suitable range for PersL (0.5–0.8eV).

Boron isotopes reveal multiple metasomatic events in the mantle beneath the eastern North China Craton

Linkages inferred between the geochemical heterogeneity of the mantle beneath eastern Eurasia and the stagnant Pacific slab documented geophysically in its mantle transition zone are as yet not clearly characterized. In this paper we report new elemental and isotopic data for boron (B) on a suite of well-characterized Cenozoic basalts (alkali basalts, basanites and nephelinites), with ocean island basalt (OIB)-like trace element signatures from western Shandong of the eastern North China Craton (NCC). Correlations between major elements (e.g., FeOT versus SiO2), trace elements (e.g., CeN/PbN versus BaN/ThN) and radiogenic isotopes (e.g., 206Pb/204Pb versus 87Sr/86Sr) suggest these basalts are derived via the mixing of melts from two mantle components: a fluid mobile element (FME; such as Ba, K, Pb and Sr) enriched component, which is most evident in the alkali basalts, and a FME depleted mantle component that is more evident in the basanites and nephelinites. The alkali basalts in this study have lower B concentrations (1.4–2.2μg/g) but higher δ11B (−4.9 to −1.4) values than the basanites and nephelinites (B=2.1–5.0μg/g; δ11B=−6.9 to −3.9), and all the samples have nearly constant B/Nb ratios between 0.03 and 0.07, similar to the observed range in B/Nb for intraplate lavas. Our high-SiO2 samples have higher δ11B than that of our low SiO2 samples, indicating that the B isotopic differences among our samples do not result from the addition of a continental crustal component in the mantle source, or direct crustal assimilation during the eruption process. The positive B versus Nb correlation suggests the B isotopic compositions of the western Shandong basalts primarily reflect the pre-eruptive compositions of their mantle sources. Correlations among B, Nd and Sr isotope signatures of the western Shandong basalts differ from those among basalts from plume settings (e.g., Azores and Hawaii), and are inconsistent with models suggesting single-step metasomatic additions to the mantle. We thus call upon multiple metasomatic events in the mantle beneath the eastern NCC in order to interpret its observed radiogenic and boron isotopic variability. The heavier δ11B, FME-enriched mantle source developed during an older event, while metasomatism by melts from the stagnant Pacific plate in the MTZ led to the development of a FME-depleted mantle source at greater depths with a lower δ11B.

Mechanism of electron multiplication due to charging for a SiO2 sample with a buried microstructure in SEM: A simulation analysis

This study investigates the mechanism of electron redistribution and multiplication for a SiO2 sample with a buried structure in scanning electron microscopy by numerical simulation. The simulation involved electron scattering and internal charge transport in the sample, the tracking of emitted secondary electrons (SEs), and the generation of tertiary electrons (TEs) produced by returned SEs due to charging of the sample. The results show that a buried grounded structure causes a non-uniform distribution of surface potential, and an electric field above the surface. As a result, although the number of escaped SEs above the margin of the buried structure decreases, the number of generated TEs increases more, leading to a final current of electrons that include escaped SEs and increased TEs. This multiplication of SEs might make a crucial contribution to the abnormal negative-charging contrast in SEM. During the electron beam irradiation, the variation in the number of total escaped electrons presents an obvious increase after an initial slight decrease, which corresponded to the transient characteristics of gray levels in SEM images from dark to abnormally bright.

Interface modification of MoS2/SiO2 leading to conversion of conduction type of MoS2

Few-layer MoS2 prepared by the chemical vapor deposition method is deposited on SiO2 samples with/without sulfide treatment in order to experimentally study the mechanism of conduction-type conversion in MoS2. The MoS2 thin film deposited on a SiO2 substrate with sulfide treatment shows n-type behavior, whereas the MoS2 thin film deposited on a SiO2 substrate without sulfide treatment exhibits p-type behavior. Experimental identification confirms that n-type conversion is due to a combined effect of the broken SiO bonds and the formation of SiS bonds at the SiO2 surface that results in the removal of oxygen dangling bonds and a change in the MoS2SiO2 interaction.

Dehydrogenation of methylcyclohexane to toluene over partially reduced silica-supported Pt-Mo catalysts

A series of bifunctional Pt/Mo(x)-SiO2 catalysts were investigated in the context of the hydrogen storage using the methylcyclohexane (MCH)-toluene-hydrogen cycle. The performance of partially reduced catalysts for hydrogen production was evaluated in the MCH dehydrogenation reaction carried out in a fixed-bed flow reactor at 673K and total hydrogen pressure of 2.2MPa. The catalysts with different acidity and Mo loading (4.1–12.7wt.%) were prepared by impregnation of the calcined Mo(x)-SiO2 samples with Pt precursor. The oxide catalyst precursors were characterized by chemical analysis (ICP-AES), N2 physisorption at 77K, X-ray diffraction (XRD), Raman spectroscopy and temperature-programmed reduction (H2-TPR) techniques whereas the partially reduced samples were characterized by temperature-programmed adsorption of ammonia (TPD-NH3), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The catalyst having optimized Mo loading (8.0wt.%) was the most active and its best catalytic performance was attributed to the high dispersion of MoO2 and Pt° phases and its lowest deactivation by coke formation. The activity drop of the catalysts having larger Mo loading (10.6 and 12.7wt.%) was linked with formation of MoOx-Pt core-shell nanoparticles, as confirmed by HRTEM.

Bias-polarity-dependent resistance switching in W/SiO2/Pt and W/SiO2/Si/Pt structures.

SiO2 is the most significantly used insulator layer in semiconductor devices. Its functionality was recently extended to resistance switching random access memory, where the defective SiO2 played an active role as the resistance switching (RS) layer. In this report, the bias-polarity-dependent RS behaviours in the top electrode W-sputtered SiO2-bottom electrode Pt (W/SiO2/Pt) structure were examined based on the current-voltage (I-V) sweep. When the memory cell was electroformed with a negative bias applied to the W electrode, the memory cell showed a typical electronic switching mechanism with a resistance ratio of ~100 and high reliability. For electroforming with opposite bias polarity, typical ionic-defect-mediated (conducting filament) RS was observed with lower reliability. Such distinctive RS mechanisms depending on the electroforming-bias polarity could be further confirmed using the light illumination study. Devices with similar electrode structures with a thin intervening Si layer between the SiO2 and Pt electrode, to improve the RS film morphology (root-mean-squared roughness of ~1.7 nm), were also fabricated. Their RS performances were almost identical to that of the single-layer SiO2 sample with very high roughness (root-mean-squared roughness of ~10 nm), suggesting that the reported RS behaviours were inherent to the material property.

Tailoring the Subnano Silica Structure via Fluorine Doping for Development of Highly Permeable CO2 Separation Membranes

AbstractThe fluorine doping of a silica matrix was proposed in the design of enlarged and uniform networks for highly permeable CO2/CH4 separation membranes. Fluorine doping effectively created a tunable network size, and the order of pore sizes increased with increases in the F concentration: F−SiO2 (F/Si=2/8)>F−SiO2 (F/Si=1/9)>SiO2. F−SiO2 (F/Si=1/9) membranes showed high CO2 permeance (4.1×10−7 mol m−2 s−1 Pa−1) with high CO2/CH4 selectivity (≈300) at 35 °C, due to the enlarged and uniform networks compared with those of SiO2. Fluorine doping was effective in preventing the formation of a 2nd Si−O in the 4‐membered ring (MR) of the SiO4 tetrahedra. F−SiO2 samples with smaller fractions of 4 MR and a smaller ring in silica, contain large fractions of larger rings (>5 MR), resulting in enlarged network structure and an increase in the average pore size, which translates to a higher permeance for larger molecules.

Thermal and spectroscopic properties of the nano-system (ZnO(1−x)SiO2(x))

Structural and thermal properties of the investigated nano-matrix ZnO(1−x)SiO2(x) samples were characterized by various techniques such as X-ray analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). IR spectroscopic analysis in the frequency range 400–4000 cm−1 is used here to investigate the new nano-system at room temperature. The variation of enthalpy (ΔH) with the concentration of SiO2 nanoparticles for the five systems of the ZnO(1−x)SiO2(x) matrix is determined. Seven different fundamental modes have been investigated. All of the vibrations of the investigated nano-system (ZnO(1−x)SiO2(x)) were found to be 449 cm−1, 469 cm−1, 798 cm−1, 959 cm−1, 1096 cm−1, 1630 cm−1 and 3447 cm−1 correspond to normal vibrations of stretching mode of ZnO, Si – O – Si or O – Si – O bending mode, Si – O – Si symmetric stretching, vibrational mode of Si–O – Zn, Si – O – Si asymmetric stretching, bending vibration mode of adsorbed water and stretching vibration of OH group respectively in which the variations strongly support the variation of ZnO and SiO2 nanoparticles concentration in the studied matrix. Measurements and interpretation of IR spectra as a function of ZnO and SiO2 nanoparticles concentration is reported.

Low temperature heat capacity of permanently densified SiO2 glasses

A study of low temperature specific heat capacity (1–30 K) has been performed on samples of vitreous SiO2, which have been compacted under pressures up to 8 GPa to explore different glassy phases having growing density. Increasing densification by more than 21% leads to a progressive reduction of the specific heat capacity Cp and to a shift from 10 K up to about 17 K of the broad hump, the calorimetric Boson peak (BP), observed above 1 K in a Cp(T)/T3 vs. T plot. The revealed changes are not accounted for by the modifications of the elastic continuum, implying a nature of additional vibrations at variance with the extended sound waves. Increasing atomic packing of the glassy network leads to a progressively decreasing excess heat capacity over that of α-quartz, a crystalline polymorph of SiO2. By using the low-frequency Raman intensity measured in these glasses to determine the temperature dependence of the low temperature heat capacity, it has been evaluated the density of low-frequency vibrational states. The observations are compared with some theoretical pictures explaining the nature of the BP, disclosing qualitative agreement with the predictions of the Soft Potential Model and the results of a simulation study concerning the vibrations of jammed particles. This finding leads to evaluate a nanometer length scale which suggests the existence of poorly packed domains formed from several n-membered rings involving SiO4 tetrahedra. These soft regions are believed to be the main source of low-frequency vibrations giving rise to the BP.

Space weathering of silicates simulated by successive laser irradiation: In situ reflectance measurements of Fo90, Fo99+, and SiO2

AbstractPulsed‐laser irradiation causes the visible‐near‐infrared spectral slope of olivine (Fo90 and Fo99+) and SiO2 to increase (redden), while the olivine samples darken and the SiO2 samples brighten slightly. XPS analysis shows that irradiation of Fo90 produces metallic Fe. Analytical SEM and TEM measurements confirm that reddening in the Fo90 olivine samples correlates with the production of “nanophase” metallic Fe (npFe0) grains, 20–50 nm in size. The reddening observed in the SiO2 sample is consistent with the formation of SiO or other SiOx species that absorb in the visible. The weak spectral brightening induced by laser irradiation of SiO2 is consistent with a change in surface topography of the sample. The darkening observed in the olivine samples is likely caused by the formation of larger npFe0 particles, such as the 100–400 nm diameter npFe0 identified during our TEM analysis of Fo90 samples. The Fo90 reflectance spectra are qualitatively similar to those in previous experiments suggesting that in all cases formation of npFe0 is causing the spectral alteration. Finally, we find that the accumulation of successive laser pulses cause continued sample darkening in the Vis‐NIR, which suggests that repeated surface impacts are an efficient way to darken airless body surfaces.

Influence of Substrate Microstructure on the Transport Properties of CVD-Graphene

We report the study of electrical transport in few-layered CVD-graphene located on nanostructured surfaces in view of its potential application as a transparent contact to optoelectronic devices. Two specific surfaces with a different characteristic feature scale are analyzed: semiconductor micropyramids covered with SiO2 layer and opal structures composed of SiO2 nanospheres. Scanning tunneling microscopy (STM) and scanning electron microscopy (SEM), as well as Raman spectroscopy, have been used to determine graphene/substrate surface profile. The graphene transfer on the opal face centered cubic arrangement of spheres with a diameter of 230 nm leads to graphene corrugation (graphene partially reproduces the opal surface profile). This structure results in a reduction by more than 3 times of the graphene sheet conductivity compared to the conductivity of reference graphene located on a planar SiO2 surface but does not affect the contact resistance to graphene. The graphene transfer onto an organized array of micropyramids results in a graphene suspension. Unlike opal, the graphene suspension on pyramids leads to a reduction of both the contact resistance and the sheet resistance of graphene compared to resistance of the reference graphene/flat SiO2 sample. The sample annealing is favorable to improve the contact resistance to CVD-graphene; however, it leads to the increase of its sheet resistance.

Microstructuring of silicon single crystals by fiber laser in high-speed scanning mode

Subject of Study. The surface structure of the silicon wafers (substrate) with a thermally grown silicon dioxide on the surface (of SiO2/Si) is studied after irradiation by pulse fiber laser of ILI-1-20 type. The main requirements for exposure modes of the system are: the preservation of the integrity of the film of silicon dioxide in the process of microstructuring and the absence of interference of surrounding irradiated areas of the substrate. Method. Studies were carried out on silicon wafers KEF-4,5 oriented in the crystallographic plane (111) with the source (natural) silicon dioxide (SiO2) with thickness of about 4 nm, and SiO2 with 40 nm and 150 nm thickness, grown by thermal oxidation in moist oxygen. Also, wafers KHB-10 oriented in the plane (100) with 500 nm thickness of thermal oxide were investigated. Irradiation of SiO2/Si system was produced by laser complex based on ytterbium fiber pulse laser ILI-1-20. Nominal output power of the laser was 20 W, and the laser wavelength was λ = 1062 nm. Irradiation was carried out by a focused beam spot with a diameter of 25 microns and a pulse repetition rate of 99 kHz. The samples with 150 nm and 40 nm thickness of SiO2 were irradiated at a power density equal to 1,2·102 W/cm2, and the samples of SiO2 with 500 nm thickness were irradiated at a power density equal to 2,0·102 W/cm2. Scanning was performed using a two-axis Coordinate Scanning Device based on VM2500+ drives with control via a PC with the software package "SinMarkTM." Only one scan line was used at the maximum speed of the beam equal to 8750 mm/s. Morphology control of the irradiated samples was conducted by an optical microscope ZeissA1M with high-resolution CCD array. A scanning probe microscope Nanoedicator of the NT-MDT company was used for structural measurements. Main Results. It has been shown that at a single exposure of high-frequency pulsed laser radiation on SiO2/Si system, with maintaining the integrity of the SiO2 film, similar symmetric microstructures are formed on the silicon surface. We suggest that the reason for their appearance is the reconstruction of the surface of the silicon arising in the process of recrystallization of the silicon melt surface in the irradiated region of the substrate. The morphology of these microstructures is due to several factors: crystallographic orientation of the plate, original (before the thermal oxidation) reconstruction of the plate surface, elastic stresses of SiO2/Si, laser treatment (thermal, corpuscular, wave). Exposure modes for the observed structures have been determined. Practical Relevance. For the first time in the microstructuring of SiO2/Si by fiber laser in the high-speed scanning mode, images of pieces have been obtained, which can indirectly imply that the reconstruction of atoms on the silicon substrate surface occurs before the thermal oxidation. Clearly marked localization of laser energy at selected irradiation modes enables to assert the possibility of detection and control of structural defects for the elements of semiconductor electronic devices.

Preparation of CaCO3-SiO2 composite with core-shell structure and its application in silicone rubber

Abstract A new CaCO3-SiO2 composite with core-shell structure was successfully prepared by mechano-chemistry method (MCM). SEM and FTIR indicated that SiO2 particles were homogeneously immobilized on the surface of CaCO3. The well dispersion of this CaCO3-SiO2 composite into silicone rubber can not only reduce the usage amount of SiO2, but also improve the mechanical properties of silicone rubber. By the calculation, the theoretical numbers of the SiO2 particles is about 10 times as large as that of CaCO3 particles in the CaCO3-SiO2 composite. Mixing CaCO3-SiO2 composite in silicone rubber can enhance the breaking strength of the silicone rubber about 18% as high as that when mixing the pure SiO2. And the elongation at break is about 14% less than that of adding the pure SiO2 sample.

Au/MnOx/3DOM SiO2: Highly active catalysts for toluene oxidation

Three-dimensionally ordered macro-/mesoporous silica (3DOM SiO2)-supported manganese oxide and gold nanocatalysts (yAu/zMnOx/3DOM SiO2, y=0–0.95wt%; z=2.7–15.4wt% (weight percentage of Mn2O3)) were prepared using the polymethyl methacrylate-templating, incipient wetness impregnation, and polyvinyl alcohol-protected reduction methods, respectively. It is shown that the yAu/zMnOx/3DOM SiO2 samples displayed a high-quality 3DOM architecture with macropores (180–200nm in diameter) and mesopores (4–6nm in diameter) and a surface area of 220–318m2/g. MnOx nanoparticles (NPs) with a size of 18.7–25.7nm were dispersed on the surface of 3DOM SiO2, and Au NPs with a size of 3.6–3.8nm were uniformly dispersed on the surface of zMnOx/3DOM SiO2. The 0.93Au/11.2MnOx/3DOM SiO2 sample performed the best (the temperature required for achieving a 90% toluene conversion was 255°C at space velocity=20,000mL/(g h)) for toluene oxidation. It is concluded that the higher oxygen adspecies concentration, better low-temperature reducibility, and stronger interaction between Au and MnOx NPs as well as the unique bimodal porous structure were responsible for the good catalytic performance of 0.93Au/11.2MnOx/3DOM SiO2.

Quantitative analysis of Ni 2p photoemission in NiO and Ni diluted in a SiO2 matrix

In X-ray excited photoelectron emission (XPS), besides the initial excitation process, the shape and intensity of photoelectron peaks are strongly affected by extrinsic excitations due to electron transport out of the surface (including bulk and surface effects) and to intrinsic excitations due to the sudden creation of the static core hole. To make an accurate quantitative interpretation of features observed in XPS, these effects must be included in the theoretical description of the emitted photoelectron spectra. It was previously shown [N. Pauly, S. Tougaard, F. Yubero, Surf. Sci. 620 (2014) 17] that these three effects can be calculated by means of the QUEELS-XPS software (QUantitative analysis of Electron Energy Losses at Surfaces for XPS) in terms of effective energy-differential inelastic electron scattering cross-sections. The only input needed to calculate these cross-sections is the energy loss function of the media which is determined from analysis of Reflection Electron Energy Loss Spectra (REELS). The full XPS spectrum is then modeled by convoluting this energy loss cross-section with the primary excitation spectrum that accounts for all effects which are part of the initial photo-excitation process, i.e. lifetime broadening, spin–orbit coupling, and multiplet splitting. In this paper we apply the previously presented procedure to the study of Ni 2p photoemission in NiO and Ni diluted in a SiO2 matrix (Ni:SiO2), samples being prepared by reactive magnetron sputtering at room temperature. We observe a significant difference between the corresponding Ni 2p primary excitation spectra. The procedure allows quantifying the relative intensity of the c3d9L, c3d10L2, and c3d8 final states contributing to the Ni 2p photoemission spectra of the Ni2+ species in the oxide matrices. Especially, the intensity ratio in NiO between the non-local and local contributions to the 3d9L configuration is determined to be 2.5. Moreover the relative intensity ratio of the c3d9L/c3d10L2/c3d8 configurations is found to be 1.0/0.83/0.11 for both the NiO and Ni:SiO2 samples.

Laser induced fluorescence monitoring of the etching processes with the inward plasma

Laser induced fluorescence (LIF) spectroscopy has been used to monitor the etching processes in a localized plasma etching system. An inward plasma was employed for etching in which etching gas was discharged in the narrow gap between the etched sample and the entrance of an evacuating capillary tube. By observing the LIF spectrum, it was confirmed that the etch product SiF2 exists near the both Si and SiO2 sample surfaces being etched with CF4 inward plasma. The plasma gas temperature was estimated to be ∼400 K from the comparison of the LIF spectrum with the rotational simulation. LIF method was applied to the etching endpoint detection of two kinds of material, thermally-grown SiO2 on Si and spin-coated Polyimide Isoindoro Quinazorindione (PIQ) film on Si. The endpoint was detected from the onset of SiF2 production by the etching of Si substrate in the case of PIQ/Si. The signal intensity of SiF2 from the Si substrate during etching was several times larger than that from the SiO2 layer, and thus, the endpoint of SiO2 etching was detected by the abrupt increase of SiF2 signal. The etch rates of PIQ and SiO2 at the center of the capillary were determined to be 1.09 μm/min and 1.66 μm/min, respectively.

Synthesis and Optical Properties of Cu Core/Ti-Related Shell Nanoparticles in Silica Sequentially Implanted With Ti and Cu Ions

Amorphous SiO2 samples were sequentially implanted with Ti and Cu ions and were then subjected to thermal annealing at different temperatures. The structures and optical properties of the synthesized nanoparticles (NPs) have been characterized in detail. Our results clearly show that the pre-implantation of Ti ions into SiO2 could strongly affect the nucleation and thermal growth of Cu NPs. Core-shell NPs consisting of Cu cores surrounded by Ti-related shells have been revealed in silica sequentially implanted with Ti and Cu ions at the same fluence of 5 × 1016 cm−2 followed by 800 °C annealing. The synthesized NPs exhibit significantly enhanced surface plasmon resonance (SPR) absorption and improved third-order nonlinear susceptibility as compared with those in the Cu singly implanted sample. The possible mechanisms responsible for the above results have been discussed.

Influence of annealing temperature on structural and optical properties of SiO2:RE2O3 [RE = Y, Gd] powder

SiO2:RE2O3 [RE=Y, Gd] powder were prepared by wet chemical technique and the prepared binary oxides annealed at 500°C and 900°C. The crystalline structure, phase transformation, and surface morphologies of as-prepared and annealed samples were investigated by XRD and TEM. The normal transmission was measured using FTIR spectroscopy. Optical properties have been studied with UV–Vis spectroscopy and PL study. XRD results shows that the as prepared samples of SiO2:RE2O3 [RE=Y, Gd] powder has mixed phases of RE(NO3)3 and Si(OH)3. However, cubic rare earth oxide phase alone is found for annealed samples. The strain values are calculated from W–H plot for annealed samples. TEM micrograph shows that the samples are composed of individual spherical nanocrystallites at 500°C and aggregated nanocrystallites at 900°C. From the UV–Vis spectra, it is found that the position of the absorption peak is shifted toward the higher wavelength side when annealing temperature is increased. In the PL spectra, the broad emission bands are observed between 570–600nm and the presence of O–Si–O (silica) and metal oxide is confirmed by FTIR spectra.