SiO2 Glass Substrates Research Articles

Plasmonic surface nanostructuring of Au-dots@SiO2 via laser-irradiation induced dewetting

The in situ observation of Au dot formation and the self-assembly dynamics of Au nanoparticles (NPs) was successfully demonstrated via dewetting of Au thin films on SiO2 glass substrates under nano-second pulsed laser irradiation using a multi-quantum beam high-voltage electron microscope. Moreover, using electron energy-loss spectroscopy (EELS) performed in a scanning transmission electron microscope (STEM), the plasmonic properties of the formed Au/SiO2 nanostructure were analyzed to demonstrate its validity in advanced optical devices. The uniformly distributed Au NPs evolved into a dot alignment through movement and coalescence processes was demonstrated in this in situ observation. We carried out the plasmon-loss images of the plan view and the cross-section of the Au/SiO2 nanostructures were obtained at the plasmon-loss peak energy for investigate the three-dimensional distribution of surface plasmon. Furthermore, discrete-dipole approximation (DDA) calculations were used to simulate the plasmonic properties, such as the surface plasmon resonance and the surface plasmon field distribution, of isolated single Au/SiO2 nanostructures. This STEM-EELS-acquired surface plasmon map of the cross-sectional sample is in excellent agreement with the DDA calculations. This results demonstrated the influence of the contact condition between Au NP and SiO2 glass on the plasmonic properties, and may improve the technology for developing advanced optical devices.

A study of thickness dependence on omnidirectional anti-reflection SiO2 nanorod array fabricated by oblique angle deposition

In this paper, we experimentally demonstrated the oblique angle deposition silicon dioxide nanorods as good anti-reflection coating materials. The nanostructures morphologies and the optical properties were characterized by field-emission scanning electron microscopy and transmission electron microscopy. The influence of the OAD on the optical property of the SiO2 dense and SiO2 nanorods film were investigated by the spectral transmission measurement in 200-1200 nm wavelength regimes. The angle-dependent transmission from 0° to 45° incident angles results demonstrate that increased transmittance through the SiO2 nanosrods surface compared to that of the SiO2 films coated glass. The SiO2 nanorods with 800 nm-thick have transmission closed to the SiO2 film and glass substrate. In addition, the high transmission was observed for angles of incidence up to 45°. The SiO2 nanorods array makes this omnidirectional antireflection concept easily applicable to a wide range of devices.

Deposition of NaGd(WO4)2:Eu3+/Bi3+ films on glass substrates and potential applications in white light emitting diodes

NaGd(WO4)2:Eu3+/Bi3+ films were deposited on SiO2 glass substrates by spin-coating. The as-prepared films were heat treated at different temperatures. The properties of films were characterized by TG-DSC, XRD, SEM and fluorescence spectrophotometer. The TG-DSC curve indicated that films began to crystallize at about 600°C. The XRD patterns and SEM images of films annealed at 600°C, 700°C and 800°C showed that a higher temperature benefits to the higher crystallinity and induces the lower thickness. Meanwhile, it was found that the revolution of spin coating influenced the morphology of films obviously. Under the excitation at 396nm, NaGd(WO4)2:Eu3+/Bi3+ films showed characteristic emission bands originating from 5D0→7Fj (j=1, 2, 3, and 4) transitions of Eu3+ ions. It was also found that the excitation wavelength has great effect on the emission intensity.

Lens-Less Coupling of Cavity-Resonator-Integrated Guided-Mode Resonance Filter

A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consists of a grating coupler (GC) and a pair of distributed-Bragg reflectors (DBRs) on a thin-film dielectric waveguide, and provides a narrowband reflection spectrum for an incident small-diameter beam. A lens-less direct coupling of CRIGF to a single-mode optical fiber is theoretically and experimentally studied. A field-profile matching was discussed with alignment tolerance between CRIGF and the fiber. Design, fabrication, and characterization of CRIGF were described for an operation wavelength of 1540 nm. The aperture size and a nonuniform fill factors of the GC were investigated in order to realize high-efficiency coupling with an incident Gaussian beam of a 10.5-μm diameter. GeO2:SiO2 guiding core and Si-N cladding layers were deposited on a SiO2 glass substrate, and GC and DBRs were formed in the cladding layer by the electron-beam direct writing lithography. The lens-less direct coupling was demonstrated with wavelength selective coupling of the maximum efficiency of 50% and full-width at half-maximum of 1.3 nm.

Detection of dead layers and defects in polycrystalline Cu2O thin-film transistors by x-ray reflectivity and photoresponse spectroscopy analyses

Polycrystalline Cu2O films were fabricated on amorphous SiO2 glass by pulsed laser deposition at room temperature and postdeposition thermal annealing in N2 + O2 mixing gases. The authors made a phase map in annealing temperature (Tann) vs RO2 = [O2]/([O2] + [N2]) ratio and found that highly pure Cu2O films were obtained at RO2 ∼ 0.002%. The increase in Tann improved the crystal quality of the Cu2O films, and the maximum Hall mobility of ∼26 cm2/(V s) was obtained at 700 °C. Bottom-gate Cu2O thin-film transistors (TFTs) using the optimum Cu2O channels exhibited clear p-type operation; however, the largest field effect mobility is as small as the order of 10−2 cm2/(V s), indicating the existence of high-density hole trap states. Several subgap states were observed by optical absorption spectra of films and photoresponse spectroscopy of the TFTs. X-ray reflectivity analysis detected a low-density dead layer at the Cu2O–SiO2 glass substrate interface, which would be attributed to Cu diffusion into the glass substrate.

Optical waveguide and 1.54 μm photoluminescence properties in RF sputtered Er/Yb-doped ZnO thin films

The erbium-doped ZnO films were deposited on SiO2 glass and MgO crystal substrates by RF-magnetron sputtering and were characterized by the use of photoluminescence, X-ray diffraction, Rutherford backscattering spectrometry and field emission scanning electron microscopy. The results show that the films fabricated on SiO2 glass substrate are highly c-axis oriented. The Er-doped films emit photoluminescence spectra centered at 1.54μm, and the emission intensity is strongly related with substrate temperature. The waveguiding properties of the Er-doped ZnO film on SiO2 glass substrate are demonstrated by prism coupling. Both TE and TM modes are measured at 633nm.

Cooling dynamics of self-assembled monolayer coating for integrated gold nanocrystals on a glass substrate.

Picosecond time-resolved X-ray diffraction has been used to study the nanoscale thermal transportation dynamics of bare gold nanocrystals and thiol-based self-assembled monolayer (SAM)-coated integrated gold nanocrystals on a SiO2 glass substrate. A temporal lattice expansion of 0.30-0.33% was observed in the bare and SAM-coated nanocrystals on the glass substrate; the thermal energy inside the gold nanocrystals was transported to the contacted substrate through the gold-SiO2 interface. The interfacial thermal conductivity between the single-layered gold nanocrystal film and the SiO2 substrate is estimated to be 45 MW m(-2) K(-1) from the decay of the Au 111 peak shift, which was linearly dependent on the transient temperature. For the SAM-coated gold nanocrystals, the thermal dissipation was faster than that of the bare gold nanocrystal film. The thermal flow from the nanocrystals to the SAM-coated molecules promotes heat dissipation from the laser-heated SAM-coated gold nanocrystals. The thermal transportation of the laser-heated SAM-coated gold nanocrystal film was analyzed using the bidirectional thermal dissipation model.

Ferroelectric and dielectric properties in Li-doped ZnO nanorods

In the present work, Li-doped ZnO nanorods have been deposited onto SiO2 glass substrates by the simple and economical Chemical Bath Deposition method. These layers were further characterized in terms of structural, morphological, dielectric and ferroelectric properties as a function of Li content. X-ray diffraction patterns revealed the highly c-oriented hexagonal wurtzite structure of the films. Both dielectric measurements and ferroelectric investigations at nano- and micro-scale pointed out the existence of a ferroelectric behavior in such doped ZnO nanostructures. This ferroelectric activity can be further enhanced by increasing the dopant content in the material.

Microstructure and Optical Properties during Annealing of DC Magnetron Sputtered LaB<sub>6</sub>/ITO Films on SiO<sub>2</sub> Substrates

Considering that nanosized LaB6 has unique optical properties and ITO has been widely applied for low-emission window glass, LaB6/ITO composite films were designed and prepared on SiO2 glass substrates by DC magnetron sputtering method in this paper. AFM and HRTEM methods were used for microstructure evolution analysis, and their IR and UV spectra were measured. Results proved that dense LaB6/ITO films with amorphous structure were deposited on the substrate with strong interface bonding. Crystallizing occurred during annealing of amorphous films, and the nanosized grains formed. Compared with the as-deposited films, the annealed films showed improved optical properties. Generally, the glass with the annealed film was available with more than 80% visible light transmittance, and good reflectance on UV light range.

High energy ion irradiation induced surface patterning on a SiO2 glass substrate

Experimental results about formation of self-organized surface patterns on a silica glass substrate due to irradiations with high energy Au ions at various angles of incidences have been reported in this paper. Pattern formations are found to vary significantly from theoretical predictions. Orientation, growth of ripples and ripple characteristics observed here do not conform to established results of low energy heavy-ion irradiation studies. High energy Au ion-induced effects (e.g., surface stress, mass redistribution and surface current) have been suitably invoked to explain observed phenomena.

Reflective photoluminescence fiber temperature probe based on the CdSe/ZnS quantum dot thin film

A reflective fiber temperature sensor based on the optical temperature dependent characteristics of a quantum dots (QDs) thin film is developed by depositing the CdSe/ZnS core/shell quantum dots on the SiO2 glass substrates. As the temperature is changed from 30 to 200°C, the peak wavelengths of PL spectra from the sensing head increase linearly with the temperature, while the peak intensity and the full width at half maximum (FWHM) of PL spectra vary exponentially according to the specific physical law. Using the obtained temperature-dependent peak-wavelength shift, the average resolution of the designed fiber temperature sensor can reach 0.12 nm/°C, while it reaches 0.056 nm/°C according to the FWHM of PL spectrum.

Effects of ion and nanosecond-pulsed laser co-irradiation on the surface nanostructure of Au thin films on SiO2 glass substrates

Ion irradiation and short-pulsed laser irradiation can be used to form nanostructures on the surfaces of substrates. This work investigates the synergistic effects of ion and nanosecond-pulsed laser co-irradiation on surface nanostructuring of Au thin films deposited under vacuum on SiO2 glass substrates. Gold nanoparticles are randomly formed on the surface of the substrate after nanosecond-pulsed laser irradiation under vacuum at a wavelength of 532 nm with a repetition rate of 10 Hz and laser energy density of 0.124 kJ/m2. Gold nanoparticles are also randomly formed on the substrate after 100-keV Ar+ ion irradiation at doses of up to 3.8 × 1015 ions/cm2, and nearly all of these nanoparticles are fully embedded in the substrate. With increasing ion irradiation dose (number of incident laser pulses), the mean diameter of the Au nanoparticles decreases (increases). However, Au nanoparticles are only formed in a periodic surface arrangement after co-irradiation with 6000 laser pulses and 3.8 × 1015 ions/cm2. The periodic distance is ∼540 nm, which is close to the wavelength of the nanosecond-pulsed laser, and the mean diameter of the Au nanoparticles remains at ∼20 nm with a relatively narrow distribution. The photoabsorption peaks of the ion- or nanosecond-pulsed laser-irradiated samples clearly correspond to the mean diameter of Au nanoparticles. Conversely, the photoabsorption peaks for the co-irradiated samples do not depend on the mean nanoparticle diameter. This lack of dependence is likely caused by the periodic nanostructure formed on the surface by the synergistic effects of co-irradiation.

Fabrication of BaSi2 films on (111)‐oriented Si layers formed by inverted Al‐induced crystallization method on glass structure

AbstractThe formation process of high‐quality BaSi2 films on glass substrates was investigated. A polycrystal‐Si/Al/SiO2 structure was prepared by means of the inverted Al‐induced crystallization technique. Electron backscatter diffraction (EBSD) measurements revealed that the crystal orientation of the grown Si layer varied significantly depending on the Al/Si thickness: The (111) orientation fraction reached 97% for the 50‐nm‐thick sample and the (100) orientation fraction reached 88% for the 200‐nm‐thick sample. These oriented Si layers on SiO2 glass substrates were used as templates for BaSi2 growth. The θ ‐2θ X‐ray diffraction patterns indicated the formation of BaSi2 films. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of nanosecond-pulsed laser irradiation on nanostructure formation on the surface of thin Au films on SiO2 glass substrates

In this study, we investigated nanostructure formations on the surface of Au thin films deposited on SiO2 glass substrates after nanosecond-pulsed laser irradiation, also the correlation between the nanostructures parameters and the photoabsorption peak. Spherical Au nanoparticle/SiO2 glass nanocomposites were formed on the surface of the Au thin films deposited on the SiO2 glass substrates after nanosecond-pulsed laser irradiation in air with a wavelength of 532nm at a repetition rate of 2Hz and a laser energy density of 0.7kJ/m2. Au nanoparticles were periodically arranged on the substrates under laser irradiation perpendicular to the direction of the electrical field vector of the laser light, the average diameter of Au nanoparticles was increased from 59.3 to 67.4nm and the average distance of the laser induced periodical structure was decreased from 1.3 to 1.0μm as the number of laser pulses increased from 1000 to 1500. After 2000 pulses irradiation, an additional laser irradiation induced periodical structure was formed in the direction parallel to the electrical field vector of the laser. The average periodicity of this nanostructure perpendicular to the initial nanostructure was 560nm, which is close to the wavelength of the nanosecond-pulsed laser used in this study. The average diameter of these Au nanoparticles is 41.9nm which is smaller than that of the Au nanoparticles formed after 1000 pulses irradiation. Au nanoparticles were generally dispersed on the surface while some were embedded in the substrate. After 1500 pulses irradiation, the diameter of the Au nanoparticles on the Au(30nm)/SiO2(0.8mm) is relatively larger than that of the Au nanoparticles on the Au(20nm)/SiO2(0.1mm). Each of laser irradiated sample showed an own photoabsorption peak clearly in this study. Furthermore, effects of the average diameter of the Au nanoparticles on the photoabsorption peak are discussed.

Luminescent high temperature sensor based on the CdSe/ZnS quantum dot thin film

A high temperature sensor based on the multi-parameter temperature dependent characteristic of photoluminescence (PL) of quantum dot (QD) thin film is demonstrated by depositing the CdSe/ZnS core/shell QDs on the SiO2 glass substrates. The variations of the intensity, the peak wavelength and the full width at half maximum (FWHM) of PL spectra with temperature are studied experimentally and theoretically. The results indicate that the peak wavelength of the PL spectra changes linearly with temperature, while the PL intensity and FWHM vary exponentially for the temperature range from 30 °C to 180 °C. Using the obtained temperature dependent optical parameters, the resolution of the designed sensor can reach 0.1 nm/°C.

Ion irradiation synthesis of Ag–Au bimetallic nanospheroids in SiO2 glass substrate with tunable surface plasmon resonance frequency

Ag–Au bimetallic nanospheroids with tunable localized surface plasmon resonance (LSPR) were synthesized by 100 keV Ar–ion irradiation of 30 nm Ag–Au bimetallic films deposited on SiO2 glass substrates. A shift of the LSPR peaks toward shorter wavelengths was observed up to an irradiation fluence of 1.0 × 1017 cm−2, and then shifted toward the longer wavelength because of the increase of fragment volume under ion irradiation. Further control of LSPR frequency over a wider range was realized by modifying the chemical components. The resulting LSPR frequencies lie between that of the pure components, and an approximate linear shift of the LSPR toward the longer wavelength with the Au concentration was achieved, which is in good agreement with the theoretical calculations based on Gans theory. In addition, the surface morphology and compositions were examined with a scanning electron microscope equipped with an energy dispersive spectrometer, and microstructural characterizations were performed using a transmission electron microscope. The formation of isolated photosensitive Ag–Au nanospheroids with a FCC structure partially embedded in the SiO2 substrate was confirmed, which has a potential application in solid-state devices.

Double-Layered Ge Thin Films on Insulators Formed by an Al-Induced Layer-Exchange Process

A large-grained (111)-oriented Ge thin film is achieved on a SiO2 glass substrate using an Al-induced crystallization (AIC) technique. Low-temperature (350 °C) AIC of an amorphous Ge thin film (50 nm thickness) resulted in a self-organized double-layered structure of polycrystalline Ge layers. The top Ge layer consisted of randomly oriented small grains (1 μm diameter) with a high defect density; in contrast, the bottom Ge layer was of high quality. Based on the growth model, we annihilated the top Ge layer using preferential etching. The bared bottom Ge layer provided a (111)-oriented area fraction of 99% and an average grain size of 90 μm. This Ge layer appears promising for use in Ge-based thin-film devices, as well as a heteroepitaxial seed layer for group III–V compound semiconductors, aligned nanowires, and other advanced materials.

Effect of laser radiation on multi-wall carbon nanotubes: study of shell structure and immobilization process

Multi-wall carbon nanotubes (MWCNTs) with diameters between 10 and 15 nm were transferred and immobilized onto SiO2 glass substrates by ultraviolet matrix assisted pulsed laser evaporation (UV-MAPLE). Toluene was chosen as solvent material for the preparation of the composite MAPLE targets. An UV KrF* (λ = 248 nm, τ FWHM ≅ 25 ns, ν = 10 Hz) excimer laser source was used for the irradiation experiments. The effects of incident laser fluence on the structure of the laser transferred MWCNTs was investigated by high resolution transmission electron microscopy and Raman spectroscopy. The surface morphology of the laser processed MWCNTs was investigated by field emission scanning electron microscopy and atomic force microscopy in acoustic (dynamic) configuration. Network-like structures constituted by individual nanotubes and nanotube bundles were created onto solid substrates. Changes in the nanotubes’ shell structure can be induced through the tuning of the laser fluence value incident onto the composite MAPLE targets.

P-Type Sb2Te3 and n-Type Bi2Te3 Films for Thermoelectric Modules Deposited by Thermally Assisted Sputtering Method

We developed a thermally assisted sputtering method (TASM) based on direct current magnetron sputtering to increase the rates of deposition of Sb2Te3 and Bi2Te3 films. The sputtering target was heated with the thermal energy of Ar plasma without any additional heating systems. The stoichiometric Sb2Te3 (p-type) and Bi2Te3 (n-type) films were obtained by TASM. The maximum deposition rate of the films was approximately 1.6 µm/min, which is large for a sputtering method. The differences in the composition ratio between the sputtering target and the deposited films were as small as 3.6 (p-type) and 1.5% (n-type). TASM was applied to the fabrication of a flexible thermoelectric film module. The generation properties of the film module coincided with the values that were estimated on the basis of the thermoelectric properties of films deposited on a SiO2 glass substrate. These results indicate that TASM is useful for fabricating thermoelectric film modules.

Grain boundary character distribution and texture evolution during surface energy-driven grain growth in nanocrystalline gold thin films

The evolution of grain boundary microstructure during annealing in sputtered gold thin films was investigated on the basis of FEG-SEM/EBSD/OIM analyses of nanocrystalline microstructure, in order to find a clue to the precise control of grain boundary microstructure for development of high performance polycrystalline thin films. Remarkably high fractions of coincidence site lattice (CSL) boundaries with specific Σ values such as Σ1, Σ3, Σ7, Σ13, Σ19 and Σ21 occurred in the gold thin film specimens on Pyrex glass substrate by annealing in air. The occurrence of higher fraction of these specific low-Σ boundaries is probably attributed to the evolution of a very sharp {111}-textures of different degrees which results from the preferential growth of {111}-oriented grains due to surface energy-driven grain growth. The fraction of low-Σ CSL boundaries increased with increasing area fraction of {111}-texture. The grain boundary character distribution in the gold thin film specimens was strongly affected by the annealing atmosphere and substrate materials. The sharpness of {111}-texture in the specimen annealed in low-vacuum was weaker than that in the specimen annealed in air, and an extraordinarily high fraction of Σ3 CSL boundaries occurred. The grain growth of gold thin film specimens on SiO2 glass substrate was much slower than that of specimens on Pyrex glass substrate. The fraction of low-Σ CSL boundaries observed for the gold thin film specimens on SiO2 glass substrate was lower than that in the specimens on Pyrex glass substrate. The inverse cubic root Σ dependence of low-Σ CSL boundaries in the gold thin film specimens was discussed in connection with the process of the evolution of grain boundary microstructure.