Fused Quartz Glass Research Articles

Expansivity of Fused Quartz Glass Measured Within 6×10-10K-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6 \ imes 10^{-10}\\,\ ext{K}^{-1}$$\\end{document}

A method is described to measure the thermal expansion coefficient of fused quartz glass. The measurement principle is to monitor the change in resonance frequency of a Fabry–Perot cavity as its temperature changes; the Fabry–Perot cavity is made from fused quartz glass. The standard uncertainty in the measurement was less than 0.6 (nm·m-1)·K-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\ extrm{nm}{\\cdot } \ extrm{m}^{-1}){\\cdot }\ extrm{K}^{-1}$$\\end{document}, or 0.15 %. The limit on performance is arguably uncertainty in the reflection phase-shift temperature dependence, because neither thermooptic nor thermal expansion coefficients of thin-film coatings are reliably known. However, several other uncertainty contributors are at the same level of magnitude, and so any improvement in performance would entail significant effort. Furthermore, measurements of three different samples revealed that material inhomogeneity leads to differences in the effective thermal expansion coefficient of fused quartz; inhomogeneity in thermal expansion among samples is 24 times larger than the measurement uncertainty in a single sample.

Theoretical and experimental investigation on material removal mechanism in dual-rotation polishing of fused silica glass

Fused silica glass is utilized extensively in various optical components owing to its excellent optical properties, but its high hardness and brittleness make it difficult to process with high surface accuracy and low subsurface damage. To solve this problem, a series of experiments is carried out to explore the mechanism of material removal during dual-rotation polishing of fused quartz glass. A predictive model is proposed to predict the material removal rate and the microtopography of polished surface. This model considers fundamental physics of the dual-rotation polishing process, for instance, the surface micro-topography and the pressure distribution of the polishing pad, the brittle–ductile material removal mechanism, the planetary motion during the polishing, and the influence of chemical reactions. The reliability and accuracy of the model are quantitatively evaluated through practical experiments. It is turned out that the simulated results reasonably agree with the experimental data. In addition, simulation experiments show that a Gaussian removal function with a strong central peak can be obtained when the eccentricity is 0.9 and the rotating speed ratio is between −10 and −1. This indicates that the theoretical model can be successfully applied to the prediction and optimization of polishing processes.

Surface and subsurface damage of fused quartz glass induced by shear-thickening polishing

Fused quartz glass is widely used in the civil and national defense fields. Shear-thickening polishing (STP) technology is highly efficient for processing quartz glass. However, the surface and subsurface damage (SSD) caused by STP have yet to be studied. In this study, the SSD characteristics of quartz glass after STP were examined using chemical etching and nanoindentation tests. The Sa (average roughness) of the fused quartz glass after 30 min of STP was 1.6 nm and the embedded depth of impurities was approximately 30 nm. The 3D morphology of the Beilby layer was sensitive to the chemical etching time, disappearing when the etching time was 120 s (at which point the Beilby layer with a depth ranging from 97 to 144 nm was completely removed). From various analysis methods, it can be inferred that the SSD depth was between 4.8–6.7 μm. To confirm that the above SSD came from the grinding or STP process, the polished fused silica glass was etched for 150 min to remove the SSD, after which it was polished for 30 min to regain its smooth surface; the workpieces were then etched again and the Sa and 3D morphology were compared with the workpiece which had no damage removal. The results showed that STP did not introduce new SSD and was a near-lossless polishing technique under the conditions used in this study. STP can achieve an extremely low surface roughness, efficiently; however, the depth of material removal is insufficient, and the SSD caused by the grinding process remains.

Expansivity of Fused Quartz Glass Measured with 6 x 10-10/K

Thermal expansion sometimes dominates uncertainty in a precision measurement. A cell-based refractometer has been designed at NIST which targets 10−6 relative uncertainty in the measurement of helium refractivity; in terms of absolute refractive index at ambient conditions, the accuracy goal is 3 × 10−11. To achieve this level of accuracy, the length of a 0.5 m gas cell would need to be known within 100 nm. This is achievable when cell length is measured by coordinate-measuring machine at 20 °C. However, the refractometer will operate at the thermodynamically known fixed-points of water and gallium, near 0 °C and 30 °C, respectively. The cell is made from fused quartz glass, which has a nominal thermal expansion coefficient of 0.4 (μm/m)/K. Therefore, to scale the accuracy of the dimensional metrology across 20 °C to the triple-point of water requires that the thermal expansion coefficient of fused quartz glass is known within 10 (nm/m)/K, or 2.5 %. A method is described to measure the thermal expansion coefficient of fused quartz glass. The measurement principle is to monitor the change in resonance frequency of a Fabry–Perot cavity as its temperature changes; the Fabry–Perot cavity is made from fused quartz glass. The standard uncertainty in the measurement was less than 0.6 (nm/m)/K, or 0.15 %. The limit on performance is arguably uncertainty in the reflection phase-shift temperature dependence, because neither thermooptic nor thermal expansion coefficients of thinfilm coatings are reliably known. However, several other uncertainty contributors are at the same level of magnitude, and so any improvement in performance would entail significant effort. Furthermore, measurements of three different samples revealed that material inhomogeneity leads to differences in the effective thermal expansion coefficient of fused quartz; inhomogeneity in thermal expansion among samples is 24 times larger than the measurement uncertainty in a single sample.

New Quartz And Zircon Si Isotopic Reference Materials For Precise And Accurate SIMS Isotopic Microanalysis

Here we report the Si isotope compositions of four potential reference materials, including one fused quartz glass (Glass-Qtz), one natural quartz (Qinghu-Qtz), and two natural zircons (Qinghu-Zir and Penglai-Zir), suitable for in-situ Si isotopic microanalysis. Repeated SIMS (Secondary Ion Mass Spectrometry) analyses demonstrate that these materials are more homogeneous in Si isotopes (with the spot-to-spot uncertainty of 0.090-0.102‰), compared with the widely used NIST RM 8546 (previously NBS-28) quartz standard (with the spot-to-spot uncertainty poorer than 0.16‰). Based on the solution-MC-ICP-MS determination, the recommended 𝛿30Si values are −0.10 ± 0.04 ‰ (2SD), −0.03 ± 0.05 ‰ (2SD), −0.45 ± 0.06 ‰ (2SD), and −0.34 ± 0.06 ‰ (2SD), for Glass-Qtz, Qinghu-Qtz, Qinghu-Zir, and Penglai-Zir, respectively. Our results reveal no detectable matrix effect on SIMS Si isotopic microanalysis between the fused quartz glass (Glass-Qtz) and natural quartz (Qinghu-Qtz) standards. Therefore, we propose that this synthetic quartz glass may be used as an alternative, more homogenous standard for SIMS Si isotopic microanalysis of natural quartz samples.

Modeling and experimenting of disc hydrodynamic polishing process for ultra-smooth surfaces

The machining of ultra-smooth surfaces has always been a significant research topic in the fields of optics fabrication. In this paper, disc hydrodynamic polishing (DHDP) process with a novel polishing tool is proposed to produce ultra-smooth surface with sub-nanometer scale surface roughness (Ra < 1 nm) and undamaged sub-surface. In order to explore the principle of the ultra-smooth surface generation in the DHDP process, the material removal mechanism and evolution mechanism of micro-morphology of polished surface were firstly studied by preliminary experiments. Then, theoretical material removal and surface simulation modeling are established on the basis of computational fluid dynamics (CFD), fractal theory for rough surfaces, particle contact mechanics, and erosion mechanisms in DHDP. Finally, a series of polishing experiments was performed on fused quartz glass to verify the theoretical model, which could be applied to predict surface topography and guide the ultra-smooth surface polishing process. The results indicated that the peak-to-valley (PV) value and waviness of the workpiece were reduced in the nanometer level under the erosion action of abrasive particles. Moreover, the surface roughness Ra and PV values decreased with the increase of rotation speed and polishing time. The analysis of power spectral density (PSD) results illustrates that high rotation speed of tool and polishing time (less than 60 min) can reduce the high-spatial-frequency errors distinctly, and the longer polishing time (above 60 min) can also influence on the mid-spatial-frequency errors.

Measurement of Nanometre-Scale Gate Oxide Thicknesses by Energy-Dispersive X-ray Spectroscopy in a Scanning Electron Microscope Combined with Monte Carlo Simulations.

A procedure based on energy-dispersive X-ray spectroscopy in a scanning electron microscope (SEM-EDXS) is proposed to measure ultra-thin oxide layer thicknesses to atomic scale precision in top-down instead of cross-sectional geometry. The approach is based on modelling the variation of the electron beam penetration depth and hence the depth of X-ray generation in the sample as a function of the acceleration voltage. This has been tested for the simple case of silica on silicon (SiO2/Si) which can serve as a model system to study gate oxides in metal-on-semiconductor field-effect transistors (MOS-FETs). Two possible implementations exist both of which rely on pairs of measurements to be made: in method A, the wafer piece of interest and a reference sample (here: ultra-clean fused quartz glass for calibration of the effective k-factors of X-ray lines from elements O and Si) are analysed at the same acceleration voltage. In method B, two measurements of the apparent O/Si ratio of the same wafer sample need to be made at different acceleration voltages and from their comparison to simulations the SiO2 layer thickness of the sample can be inferred. The precision attainable is ultimately shown to be limited by surface contamination during the experiments, as very thin carbonaceous surface layers can alter the results at very low acceleration voltages, while the sensitivity to ultra-thin surface oxides is much reduced at higher acceleration voltages. The optimal operation voltage is estimated to lie in the range of 3–15 kV. Method A has been experimentally verified to work well for test structures of thin oxides on Si-Ge/Si.

High-performance acousto-optic modulator based on environmentally favorable Ge20Sb15Se65 chalcogenide glass

Acousto-optic (AO) properties of an environmentally friendly Ge20Sb15Se65 chalcogenide glass were investigated, and the results show that Ge20Sb15Se65 glass was a potential material for manufacturing AO modulator (AOM) because its composition possesses excellent performance of high optical quality and transmission in the infrared region spectral, non-toxic, high glass transition temperature, strong mechanical strength, easy to fabricate in large bulk, and isotropic homogeneity. Particularly, its outstanding AO figure of merit (M2 = 407 × 10−15 s3/kg) was approximately 270 times that of fused quartz glass, making it attractive for AO device designs. Herein, the construction of the AOM based on Ge20Sb15Se65 glass as AO material was performed, and we obtained a high diffraction efficiency of 73.4% at a high acoustic frequency of 160 MHz and an extremely low radio-frequency (RF) power of 0.25 W when the laser beam at 1550 nm was controlled. To our best knowledge, the results of initial tests on the AOM prepared from Ge–Sb–Se chalcogenide glass were first reported. Such an AOM design enriches the family of AO devices and exploits the route for the practical application of chalcogenide glass.

Theoretical modeling and experimental analysis of single-grain scratching mechanism of fused quartz glass

Abstract Surface and subsurface damage, including cracks, scratches, microcracks, and residual stress, is inevitable when fabricating fused quartz glass because of their high brittleness and low fracture toughness. Single-grain scratching mechanism of fused quartz glass is examined using smoothed particle hydrodynamics (SPH) to clarify the mechanisms of material removal and produce crack-free optical surfaces. Single diamond grain experiments were conducted to validate the proposed SPH model, which predicts the critical depth of approximately 0.20 μm for ductile–brittle transition in fused quartz glass. Both simulation and experimental results indicate that three removal regimes, namely, complete ductile, ductile–brittle transform, and complete brittle modes, are involved in the material removal process. SPH simulation helps identify the location of crack formation and morphology of crack propagation during scratching. Thus, the SPH model is used to simulate the single grain scratching process under different conditions. Simulation results reflect that changing the scratching speed will lead to a remarkably different mechanism of crack initiation and propagation compared with changing the scratching depth. Effects of scratching depth and speed on scratching force and residual stress are also discussed thoroughly in the simulation analysis.

Finite-Element Simulation of the Eigen Frequency Spectrum of the Cylindrical Resonator with Geometrical Imperfectness

The solid-state wave gyroscope belongs to the class of the so-called Coriolis vibratory gyroscopes. They are industrially produced, as a rule, in two versions: precise solid-state wave gyroscopes with expensive fused quartz resonators, and devices of low accuracy with metal resonators. The use of metal for the manufacture of a solid-state wave gyroscope resonator for inertial systems of medium and low accuracy can significantly simplify the design of the device and reduce its cost, however, the low-quality factor of the metal resonator and the instability of its dissipative characteristics limit the accuracy characteristics of the solid-state wave gyroscope. The use of high-quality precision fused quartz glass resonators in such solid-state wave gyroscopes is unacceptable because of their high cost. The purpose of the work is to study the characteristics of inexpensive quartz resonators made from industrially produced fused quartz tubes, with the aim of creating a medium-accuracy solid-state wave gyroscope. Using the finite element method, the main types of geometric heterogeneities arising from the production of such resonators and their influence on their spectral characteristics are investigated. The experimental results allow us to draw conclusions about the most significant defects affecting the performance and accuracy of the solid-state wave gyroscopes

Theoretical and experimental analysis of material removal and surface generation in novel fixed abrasive lapping of optical surface

Abstract Fixed abrasive machining, which overcomes the lack of determinacy and efficiency of current loose abrasive polishing or lapping processes, is an alternative technology for fabricating large-aperture aspheric surfaces with high finishing efficiency and high-quality surface finish. A novel fixed abrasive lapping (NFAL) tool, which combines computer-controlled optical surfacing and conventional fixed abrasive lapping process, is introduced in this study to produce off-axis aspheric surfaces efficiently while surface state is controlled and subsurface damage (SSD) is avoided. The removal mechanism analysis shows that fused quartz glass is primarily removed in ductile regime and the SSD depth is 14.7 μm when the tool load is 25 N. The material removal volume is linear with the machining time under the ductile removal mode. The material removal and surface generation models are developed on the basis of the calculation of the spatial distribution of abrasive particles, the pad–particle–workpiece interactions, the single-particle abrasion mechanism, and the linearly cumulative removal of surface generation in the NFAL process. The models are verified through a series of spot and surface lapping experiments. Results show that the theoretical model can be successfully used to predict and optimize the NFAL process. The spot lapping experiments indicate that the material removal volume is linear with the rotation speed, and the maximum depth is limited to the specific value that depends on the stiffness of lapping tool. The surface roughness Ra and Rz values of the measured and simulated surface data decrease with the increase in feed rate and increase with the increase in raster spacing. The power spectral density analysis indicates that high feed rate can distinctly improve the high-frequency errors, and the selection of the raster spacing can principally affect the low-frequency and middle-spatial frequency errors.

Microchannel Fabrication in Fused Quartz by Backside Laser-Induced Plasma Ablation Using 248 nm KrF Excimer Laser

Laser-induced plasma ablation (LIPA) using a 248 nm KrF excimer laser was investigated for microchannel fabrication. Examination of the morphology in relation to ablation performance was emphasized, and a synthetic LIPA mechanism model was proposed based on the results. Backside LIPA with a metal target on the bottom can be attributed to a combination of two phenomena: laser-induced plasma vaporization thermal ablation from the metal target below and enhanced laser–glass direct interaction from the plasma residuum. The laser absorption enhancement of quartz substrate resulting from the metal residuum was validated clearly using absorption spectrum measurements. The influence of laser parameters on the etching quality during LIPA was also analyzed for processing optimization. Finally, fused quartz glass microchannels of outstanding surface quality and dimension uniformity were implemented. The channel depth was 28 μm, and the bottom surface roughness was better than several hundred nanometers.

Mechanism of material removal by fixed abrasive lapping of fused quartz glass

In this paper, a novel fixed-abrasive lapping process to finish off-axis aspheric surfaces efficiently is proposed. The lapping mechanism of fused quartz glass was evaluated using the novel fixed-abrasive pad tool. The applied load and not the rotation speed and feed rate is the key factor affecting the material removal mode of fused quartz glass in the fixed-abrasive lapping process. Analysis of surface characteristic and subsurface damage indicates that lower applied load produces more ductile mode removal and that the removal on fused quartz glass can be changed from brittle fracture to ductile regime if the applied load is less than 25 N. The material removal rate (MMR) increases as the applied load is increased, which further increases the surface roughness. In addition, the MMR increases and the surface roughness decreases as the rotation speed is increased or the feed rate is deceased. A theoretical model for predicting the maximum SSD depth of the specimens during lapping was developed. The model can predict well that the maximum SSD depth increases with increasing applied load.

Structural and electric response of ITO/In2O3 transparent thin film thermocouples derived from RF sputtering at room temperature

Transparent thin film thermocouples have unique characteristics that it can be applied when permit minimal optical interference at in-situ temperature measurement. ITO/In2O3 thin film thermocouples were prepared on fused quartz glasses at room temperature by RF magnetron sputtering. For contrast, ITO thin films post-annealed at different temperatures were investigated accordingly. All films showed good conductivities, smooth surface morphology and high transmission, indicating negligible affection of the post-annealing temperature. The as-deposited ITO film has a Seebeck coefficient of 84.4 µV oC−1. The thermoelectric voltage of 13.6 mV and significantly lower drift rate of 2.39 °C h−1 were obtained at 190 °C for ITO/In2O3 thin film thermocouples without any heat treatment. This makes the ITO/In2O3 transparent thin film thermocouples great potential as a promising temperature sensor.

Heteroepitaxy of Highly Oriented GaN Films on Non‐Single Crystal Substrates Using a Si(111) Template Layer Formed by Aluminum‐Induced Crystallization

Growth of epitaxial III‐nitride (AlGaInN) films has long been confined to single crystal substrates which are crystallographically compatible with the hexagonal GaN (0001) surface. However, for lighting, display, and power electronics applications, growth on amorphous substrates such as fused quartz glass or on polycrystalline diamond is desirable. Several approaches to produce c‐plane oriented, textured GaN films on glass have been previously demonstrated, but are process‐intensive and limited in scalability. In this report, we demonstrate the heteroepitaxial growth of textured GaN films on fused quartz and other substrates using thin silicon film templates fabricated by aluminum‐induced crystallization (AIC). The AIC‐Si films have a uniform (&gt;95%) Si (111) oriented surface, enabling well‐developed GaN‐on‐Si epitaxial growth processes to be adapted to new substrates. GaN films grown on fused quartz using metalorganic chemical vapor deposition (MOCVD) have uniformly c‐axis oriented grains, ≈40–50 μm in size, with random in‐plane orientations similar to those of the underlying AIC‐Si template layer. Threading dislocation densities of 8.5 ± 1.8 × 109 cm−2 within regions bounded by grain boundaries are comparable to GaN films grown on single crystal Si (111) substrates. Finally, highly oriented GaN growth on AIC‐Si is also achieved on both oxidized Si (001) substrates and polycrystalline diamond, demonstrating the general applicability of this approach.

Stoichiometry and structure driven optical properties of carbon incorporated titanium oxide thin films

This study shows that the optical properties of titanium oxide films depend on their chemical composition as well as structure properties. The chemical composition as well as the structure of the sputter-deposited titanium oxide films on fused quartz glass substrates was modulated by annealing them in Ar/H2 atmosphere, experimentally investigated by various spectroscopic methods including XRD, Raman, SIMS, and UV-Vis spectroscopy and simulated by Bruggeman effective medium theory (BR-EMT) and full wave finite difference time domain (FDTD) approach. The as-deposited films are amorphous titanium oxide films with oxygen deficiency, become closer to titanium dioxide in stoichiometry, and are converted to crystalline anatase TiO2 nano-particles with particle size of ~21 nm by increasing the annealing temperature from 100 °C to 450 °C. The annealing process also allows the titanium oxide films to be spontaneously doped with environmental carbon species or coated with nano-crystalline graphitic carbon. Further the FDTD simulation results indicate that the annealed titanium oxide films become porous. The chemical composition modulation, anatase crystalline formation, carbon doping and graphitic carbon coating are simultaneously achieved by the simply annealing the sputter-deposited amorphous titanium oxide thin films on fused quartz substrates at relatively low temperatures.

(Invited) Self-Aligned Four-Terminal Low-Temperature Polycrystalline-Silicon Thin-Film Transistors on Glass Substrate Using Continuous-Wave Laser Lateral Crystallization

Low-temperature (LT) polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) are indispensable for applications that involve integrating high-speed and low-power dissipation complementary metal-oxide-semiconductor (CMOS) circuits onto a glass substrate. The on-current of the LT poly-Si TFTs can be enhanced by fabricating a high-quality poly-Si film on the glass substrate. In the current study, the fabrication of these transistors was achieved using continuous-wave laser lateral crystallization (CLC). This method enabled us to form a lateral poly-Si film with high quality and large grain size (the grain area was approximately 100 times larger than that of the conventional excimer-laser crystallization (ELC) poly-Si film) without damaging the substrate. A possible approach to achieve low-power dissipation is by controlling the threshold voltage (Vth). In order to control the Vth of the LT poly-Si TFTs, we fabricated self-aligned four-terminal (4T) LT poly-Si TFTs using high-quality CLC poly-Si film. These TFTs comprise metal gates on the top and bottom. The bottom metal gate was embedded in the glass substrate using a chemical mechanical polish. The top metal gate was fabricated by a self-aligned process of back surface exposure using the bottom metal gate as a photomask. This TFT was fabricated on a fused quartz glass at 550°C. The top and bottom metal gates acted as drive and control gates, respectively, or vice versa. The performance of the fabricated n-channel (n-ch) and p-channel (p-ch) self-aligned 4T CLC LT poly-Si TFTs was evaluated. To evaluate their feasibility, an E/D inverter was utilized by connecting two identical n-ch TFTs on different glass substrates, which were fabricated by identical processes.The self-aligned 4T CLC LT poly-Si TFTs showed excellent Vth controllability. The variation of the Vth of the drive gate TFT, with respect to small variation in the control gate voltage, was found to closely match the theoretically predicted values of the top and bottom gate drives for both n- and p-ch TFTs. The output characteristics of the drive TFTs were found to be sensitive to the varying magnitude of the control gate voltage. The mobility of the n-ch TFTs in the top and bottom drive TFTs was above 300 cm2/Vs. This remarkable performance may be attributed to the high-quality CLC poly-Si film. The mobility varied sensitively against the strength of the vertical electric field, which was changed by varying the control gate voltage. The s.s. values were also found to vary depending on the control gate voltage, and this variation is explained by the change in the position of the channel layer towards the side of either the drive or the control gate. By exploiting the high controllability of the 4T TFTs, an E/D inverter was fabricated and successfully operated at 2.0 V. The Vth of the self-aligned 4T CLC LT poly-Si TFTs was found to be sensitive to a 20-meV variation of the control gate voltage. Utilizing this sensitivity, we further fabricated an extended-gate pH sensor, where the control gate was connected to the glass electrodes, and the pH of the solution varied from 4.1 to 8.8. Consequently, we were able to successfully observe the variation of the drain current in the drive gate TFT depending on the strength of pH. In summary, the results suggest that the high controllability of the self-aligned 4T CLC LT poly-Si TFTs could enable us to fabricate high-speed and low-power-dissipation circuits on a glass substrate. Further, our study suggests the promising potential of such TFTs for applications involving sensor fabrication.

Nonlinear thickness and oxidation-dependent transparency and conductance of sputtered titanium suboxide nanofilms

Optically transparent and electrically conductive semiconducting titanium suboxide nanometer thick films, which are technologically important in a wide variety of applications, show a nonlinear dependency of optical and electrical properties on film thickness and oxidation time. The optical, electrical, chemical, and structural properties of the sputter-deposited titanium suboxide nanofilms on fused quartz glass at room temperature are investigated by varying the film thickness, and the additional oxidation is controlled by the duration of air exposure. The optical properties of the nanofilms are simulated by considering them as both a homogeneous film as well as an inhomogeneous film with the combination of the Lorentz Drude model and the Maxwell Garnett effective medium theory (MG-EMT). Their electrical properties are simulated with the MG-EMT. The optical transmittance, electrical conductivity, secondary ion mass spectroscopy, x-ray photoemission spectroscopy analysis, and simulation of titanium suboxide nanofilms indicate that inhomogeneous film growth and oxidation are responsible for the nonlinear dependency. The oxygen atomic ratios to titanium for the as-deposited films depend on the deposition time and vary in 1.60–1.73, while those exposed to air for seven days increase to 1.79–1.99.

Third-order nonlinear optical characteristics of bulk film effect on regioregular poly(3-dodecylthiophene) thin films fabricated by the drop-casting method

We report the morphologies and the bulk film effect on regioregular poly(3-dodecylthiophene) [RR-P3DDT] thin films fabricated with different concentrations (0.1, 0.2, 0.4 wt%) by drop-casting method using chloroform as a solvent and fused quartz glass as substrate. The measured thicknesses of the films were 220, 340 and 600 nm. The thin films were characterized by UV–Vis spectra and X-ray diffraction. The surface morphology of the thin film (600 nm) was analyzed using atomic force microscopy. The third order nonlinear susceptibility characteristics of the films were measured using Maker fringes method. These films exhibit efficient THG bulk effect with a maximum χ3 value of 1.41 × 10−10 esu obtained for 0.4 wt% concentration of RR-P3DDT revealing that this material is potentially suited for fabricating optical limiters.

Fabrication and Photocatalytic Properties of ZnSe Nanorod Films

ZnSe nanorod films grown on fused quartz glass substrates via a simple two-step synthesis protocol were demonstrated to be environmentally safe and effective recyclable photocatalysts. These films showed greatly enhanced photocatalytic activity compared to pulsed laser deposition ZnSe films in the degradation of methyl orange dye solutions. The well-crystalized ZnSe nanorods had a length of 15 µm and a diameter of 200 nm and were densely grown on the substrate. The morphology, crystal structure, crystal phase, and photophysical properties of the ZnSe nanorod films were investigated using field-emission scanning electron microscopy (FE-SEM), UV-Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM).