Si Glass Research Articles

Room-temperature pulsed laser deposition and dielectric properties of amorphous Bi3.95Er0.05Ti3O12 thin films on conductive substrates

Bi3.95Er0.05Ti3O12 (BErT) thin films were prepared on Pt/Ti/SiO2/Si and indium-tin-oxide (ITO)-coated glass substrates at room temperature by pulsed laser deposition. These thin films were amorphous with uniform thickness. Excellent dielectric characteristics have been confirmed. The amorphous BErT thin films deposited on the Pt/Ti/SiO2/Si and ITO-coated glass substrates exhibited almost the same dielectric constant of 52 with a low dielectric loss of less than 0.02 at 1 kHz. Meanwhile, the dielectric properties of the thin films had an excellent bias voltage stability and thermal stability. The amorphous BErT thin films might have potential applications in microelectronic and optoelectronic devices.

Effects of Substrate Temperature on the Properties of Silicon Oxide Films by PECVD

Under different growth conditions, silicon Oxide (SiOx) thin films were deposited successfully on Si (100) substrates and glass substrates by plasma enhanced chemical vapor deposition (PECVD). The thickness, refractive index and growth rate of the thin films were tested by ellipsometer. The effects of deposition temperature on the structure and properties of SiOx films were studied using X ray diffraction (XRD), X ray photoelectron spectroscopy (XPS) and UV-Visible spectroscopy. The results show that the SiOx films were amorphous at different deposition temperature. The peaks of Si2p and O1s shifted to higher binding energy with temperature increasing. The SiOx films had high transmissivity at the range of 400-900nm. By analyzing the observation and data, the influence of deposition parameters on the electrical properties and interface characteristics of SiOx thin film prepared by PECVD is systematically discussed. At last, SiOx thin film with excellent electrical properties and good interface characteristic is prepared under the relatively optimum parameters.

Spectroscopic ellipsometry modeling of ZnO thin films with various O2 partial pressures

ZnO films were deposited on thermally oxidized SiO2/p-type Si (100) substrates and glass substrates by DC magnetron sputtering using a metal Zn target. Three types of samples were prepared with various O2/(Ar + O2) ratios (O2 partial pressure) of 20%, 50%, and 80%. The properties of these ZnO thin films were investigated using X-ray diffraction (XRD), optical transmittance, atomic force microscopy (AFM), and spectroscopic ellipsometry in the spectral region of 1.7–3.1 eV. The structural and optical properties of ZnO thin films were affected by O2 partial pressure. Relationships between crystallinity, the ZnO surface roughness layer, and the refractive index (n) were investigated with varying O2 partial pressure. It was shown that the spectroscopic ellipsometry extracted parameters well represented the ZnO thin film characteristics for different O2 partial pressures.

Broadband Membrane Reflectors on Glass

We report here high-performance broadband membrane reflectors based on crystalline silicon nanomembrane photonic crystals. A modified polydimethylsiloxane stamp transfer technique is developed for transferring large-area silicon membranes to glass substrates. Polarization-independent broad reflectivity at 1550-nm wavelength band was obtained from Si membrane reflectors, on both silicon and glass substrates. The experimental results also agree well with simulation results.

The effects of impurity and temperature for transparent conducting oxide properties of Al:ZnO deposited by dc magnetron sputtering

Aluminum-doped zinc oxide films (ZnO:Al) were deposited on Si wafers and glass substrates by dc magnetron sputtering from a ZnO target mixed with 2 wt% Al2O3 for photovoltaic films. The effect of base pressure, additional oxygen, and substrate temperature were studied in detail. By dc magnetron sputtering at room temperature, the resistivity and the average transmittance in visible range was 2.3 × 10−3 Ω cm and 77.3%, respectively. And these were improved up to 3.3 × 10−4 Ω cm and 86% at the substrate temperature of 400 °C by high deposition rate and low impurity ambient. The mobility and the carrier concentration were improved by the increased preferred orientation of (002) plane and grain size of film with increasing deposition temperature. This advanced AZO film with good resistivity and transmittance can be expected as the front TCO of thin film solar cells.

Growth and optical properties of gadolinium aluminum nitride thin films

AbstractIn this study, c‐axis oriented AlN, GdxAl1‐xN and AlN/Gd0.05Al0.95N films have been successfully grown on both Si(100) and quartz glass substrates by DC magnetron reactive sputtering method. The XRD patterns show that the crystal structure of the film has changed after doping Gd3+. The optical constants were obtained by ellipsometry measurements. The high extinction coefficient k in the deep UV range is just in agreement with the low transmittance in the range of 250‐300 nm. The refractive index n increases as well with increasing Gd concentrations. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation of Al–Fe–Si glass that grows from the melt through a first-order transition

Microstructures of rapidly solidified Al–Fe–Si alloys demonstrate possible formation of a glassy phase, which we term q-glass, that is not a kinetically frozen liquid. Microstructural observations point out that the phase grows from the melt by a first order phase transition in the manner of a crystal, but scatters as a metallic glass. In this paper, by studying a large number of Al–Fe–Si alloys (8–22at% Fe and 5–20at% Si), we confirmed this observation and identified domains of formation of the q-glass as a primary phase, as well as a 1/1 α-cubic approximant and an icosahedral phase. Our attempts to grow such a glass in different metallic systems by substituting Fe with Ni and Co have not succeeded. We discuss several reasons why the Al–Fe–Si system might be unique.

Effect of Al4SiC4 on the Al2O3[sbnd]SiC[sbnd]SiO2[sbnd]C refractory castables performance

Carbon-containing refractories are widely used in the steelmaking process due to their outstanding properties and, in order to improve their oxidation resistance, the so-called antioxidants have often been used. Al4SiC4 is pointed out as a novel additive that presents suitable properties such as Al, but without its drawbacks. Therefore, the effect of Al4SiC4 addition to Al2O3SiCSiO2C castables designed for lining blast furnace troughs was investigated in this work. Apparent porosity, oxidation, thermogravimetric, X-ray diffraction, hot elastic modulus tests and thermodynamic calculations were carried out in order to better understand the antioxidant effects and reaction mechanisms. Additionally, the collected results were compared with those from the compositions containing other commonly used antioxidants (Si, B4C and sodium borosilicate glass). The performance of the novel additive proved to be limited as most of the carbon source used reacted earlier than the Al4SiC4 action. As a consequence, intense carbon oxidation, along with the thermal expansion mismatch among the phases during the cooling step, intensified the deterioration of the evaluated refractory material.

Near room-temperature synthesis of transfer-free graphene films

Large-area graphene films are best synthesized via chemical vapour and/or solid deposition methods at elevated temperatures (~1,000 °C) on polycrystalline metal surfaces and later transferred onto other substrates for device applications. Here we report a new method for the synthesis of graphene films directly on SiO(2)/Si substrates, even plastics and glass at close to room temperature (25-160 °C). In contrast to other approaches, where graphene is deposited on top of a metal substrate, our method invokes diffusion of carbon through a diffusion couple made up of carbon-nickel/substrate to form graphene underneath the nickel film at the nickel-substrate interface. The resulting graphene layers exhibit tunable structural and optoelectronic properties by nickel grain boundary engineering and show micrometre-sized grains on SiO(2) surfaces and nanometre-sized grains on plastic and glass surfaces. The ability to synthesize graphene directly on non-conducting substrates at low temperatures opens up new possibilities for the fabrication of multiple nanoelectronic devices.

Effect of Sputtering Current on Structure and Morphology of (Ti1-xCrx)N Thin Films Deposited by Reactive Unbalanced Magnetron Co-sputtering

(Ti1-xCrx)N thin films were deposited with various chromium currents (ICr = 0.4-1.0 A) on Si (100) wafers and glass slides by reactive unbalanced magnetron co-sputtering technique without heating and biasing the substrates. The effects of sputtering current on the structure and morphology of (Ti1-xCrx)N films was studied. The films were grown on the substrates using titanium and chromium targets in a mixed Ar and N2 atmosphere. The structure of the films was investigated by x-ray diffraction (XRD). The surface and cross-sectional morphologies of the films were examined by atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM), respectively. Furthermore, the chemical composition of the films was analyzed using energy dispersive x-ray spectroscopy (EDS). The results revealed that the (Ti1-xCrx)N thin films formed solid solutions with the fcc NaCl phase and relative Cr content (x) was figured out in the range from 0.46 to 0.81. The crystal sizes of the films calculated from Scherrer formula are about 12-13nm. AFM results indicated increasing of the roughness from 3 to 7 nm corresponding to the thickness increased from 400 to 900nm when ICr was increased. In addition, the crosssectional morphology showed dense and compact columnar.

Structure and Surface Morphology of Cr-Zr-N Thin Films Deposited by Reactive DC Magnetron Sputtering

In this study, chromium zirconium nitride (Cr-Zr-N) thin films have been prepared by reactive dc closed field unbalanced magnetron co-sputtering on Si (100) wafers and glass slides for 60min without substrate heating and biasing voltage in gas mixture of Ar and N2 with flow rates kept constant at 3.0sccm and 6.0sccm, respectively. The sputtering currents applied to Zr target were varied from 0.2 A to 0.8 A, whereas the current of Cr target was kept at 0.8 A. To investigate films structure and surface morphology as a function of Zr content, the as-deposited films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX). The results suggested that increasing in current applied to Zr target enhanced the deposition rate and also increased Zr content in the films ranging from 6.0 to 31.2 at %. The films formed a solid solution (Cr, Zr)N where Zr atoms substitute Cr atoms in the CrN lattice. The lattice parameters increased from 0.4207nm to 0.4357nm, whereas the grain sizes decreased from 11.27nm to 7.412 nm. The film structure developed with the coexistence of (111) and (200) crystallographic orientation into a mixture of nanocrystalline grains as the sputtering currents of Zr target exceeded 0.2 A. The AFM images showed smoothing surface morphology with the roughness decreased from 9.471nm to 2.437nm. Cross-sectional micrographs exhibited the microstructure evolution corresponding to the grain refinement as a result of increasing Zr discharge current.

Self-alignment of Gold Nanoparticles through the Control of Particle-substrate and Particle-particle Interactions

Gold (Au) nanostructures have been fabricated on various substrates, such as Si, ITO and quartz glass, through the position-selective deposition of Au nanoparticles. This self-aligned deposition of the nanoparticles is promoted through the electrostatic interaction between the nanoparticles and the deposition sites, which are charged negatively and positively, respectively. Prior to the nanoparticle deposition, the positively charged sites where covered with aminosilane self-assembled monolayer had been constructed on the substrate with an artificial pattern design by a lithographic method. A photolithographic process, which was based on direct photochemical modification of organic substances induced by irradiating with a vacuum ultra-violet (VUV) light, was employed so that sub-μm features down to 500nm have been successfully fabricated and provided as templates for aligning Au nanoparticles. The second method for patterning was electrochemical line drawing using a scanning probe microscope. One-dimensional arrays of Au nanoparticles with a line thickness of a single nanoparticle diameter have been successfully fabricated. In addition, by replacing a surface charged layer consisting of citric acid molecules surrounding the Au nanoparticles with alkanethiol molecules, the Au nanoparticles were neutralized so that the fabricated Au nanoparticle array in which most of the nanoparticles were separated each other was re-organized to a more closely packed structure.

Aqueous dip-coating route to dense and porous silica thin films using silica nanocolloids with an aid of polyvinylpyrrolidone

An aqueous dip-coating route without using volatile alcohols for preparing dense and porous silica thin films is presented. The films were prepared by dip-coating on Si(100) and silica glass substrates using aqueous suspension of 8–11 nm colloidal silica where no alcohols were added. The addition of polyvinylpyrrolidone (PVP) in the suspension greatly improved the wettability, allowing homogeneous films to be formed on the substrates while the substrates showed poor wettability without PVP. When the as-deposited films were fired at 500–1,000 °C, optically transparent porous films with smooth surface were obtained. The porous films had homogeneous distribution and packing of silica nanoparticles, refractive indices of 1.24–1.33, and pencil hardness lower than 6B. The porous films underwent significant densification by viscous sintering when fired at temperatures over 1,000 °C. The viscous sintering was accompanied by the progress of condensation reaction and by the structural relaxation of siloxane network, which was revealed in the infrared absorption spectra. The resulting dense films had optical transparency, smooth surface, pencil hardness over 9H and refractive indices close to that of silica glass.

Microstructure and Crystallization Kinetics Analysis of the (In15Sb85)100−xZnx Phase Change Recording Thin Films

The (In15Sb85)(100-x)Zn(x) films (x = 0 - 17.4) were deposited on nature oxidized Si wafer and glass substrate at room temperature by magnetron co-sputtering of Sb target and InZn composite target. The thermal property of the films was examined by a homemade reflectivity thermal analyzer. Microstructures of the films were analyzed by transmission electron microscope (TEM). We examined the effects of Zn addition on the thermal property, crystallization kinetics, and crystallization mechanism of the In15Sb85 recording film. As x = 0 - 17.4, thermal analysis shows that the (In15Sb85)(100-x)Zn(x) films have two phase transition temperature ranges which are 189 degrees C-215 degrees C and 300 degrees C-350 degrees C. It is found that the activation energy is increased with Zn content. This indicates that the thermal stability of amorphous state is improved by doping Zn. The optical contrasts of the films are all larger than 15%, as x = 0 - 6.2, indicating that the films have the potential in blue laser optical recording media application.

Fabrication of Tantalum nitride thin film using the low vacuum magnetron sputtering system

Tantalum nitride (TaN) thin film is attractive material as a diffusion barrier coating and used in electronics industry. TaN thin film is fabricated by some method such as DC sputtering, CVD and pulse laser deposition. In this study, TaN thin film was deposited on Si (111) wafer, soda glass substrates by reactive sputtering at low vacuum conditions for reducing energy costs. N2/Ar gas mass flow rate was ranged from 9 to 23% at N2 gas. At lower N2 gas flow, crystalline TaN thin films were obtained. Amorphous like TaN thin films were observed at other rate range using XRD. Ta oxide layer was observed between the crystalline TaN film and both of Si wafer and glass substrates by GDS depth profiling. Film thickness was 200- 400 nm. The TaN layer deposited on Si and glass substrate in 9 % N2 flow having columnar structure was observed in these films by FE-SEM.

Temperature Enhanced Large Area Nano Transfer Printing on Si/SiO2 Substrates Using Si Wafer Stamps

Metal nano structures on various substrates such as Si wafers, SiO2 surfaces, or glass are of great importance on a variety of devices.The state of the art fabrication methods like optical and electron beam lithography are wet, complex, and costly processes. Nano transfer printing (nTP) canprovide a simple, fast, and low cost alternative. In the nano transfer process, thin metal layers are deposited on a stamp and transferred by pressing the stamp on the substrate. In this study, we focus on the interface between the transferred metals and the substrate. A high adhesion can be achieved by forming silanols on the substrate surface and hydroxyl groups on the metal one. When the metal and substrate surfaces are pressed against one another, reversible metal-oxygen-silicon bonds are generated and water is formed. The nTP is strongly improved when water is removed by applying temperatures of around 200°C (390°F). Large area nano transfer printing of metal structures consisting of gold, aluminum, or magnetic Permalloy™ is demonstrated.

Ultrafine Na–Sr–Si precursor powder for sealing glass via sol–gel route

Sealing glasses have been widely used as insulating and sealing materials in the electronics industry. In this study, ultrafine Na–Sr–Si precursor powder was synthesized from sodium nitrate (NaNO3), strontium nitrate Sr(NO3)2, and tetraethoxy orthosilicate (TEOS) via the sol–gel method. Nitric acid (HNO3) or ammonia (NH4OH) was used as acid or base catalysts, respectively, to achieve miniaturization of particles. The products were characterized by X-ray diffraction, scanning electron microscope, and thermogravimetric/differential thermal analyzer. The results showed that the mean particle size for acid-catalyzed Na–Sr–Si glass precursor powder was approximately 100–700 nm, and appeared to be smaller than that for base-catalyzed Na–Sr–Si glass precursor powder. This glass precursor powder synthesized by sol–gel process has a low processing temperature of about 850–900°C compared with the processing temperature of ∼1400°C for traditional glass precursor powder. Furthermore, the coefficient of thermal expansion of this sealing glass was in the range 6.575 × 10−6–9.136 × 10−6°C−1, measured by the thermal mechanical analyzer.

Synthesis of Bismuth Oxide Thin Films Deposited by Reactive Magnetron Sputtering

In this work Bi2O3 thin films were deposited onto the Si (111) and soda lime glass substrates by the reactive direct current magnetron sputtering system using pure Bi as a sputtering target. The dependences of electro-optical characteristics of the films on the substrate type and temperature were investigated. Transmittance and reflectance of the Bi2O3 films were measured with ultraviolet and visible light spectrometer. It was found that the substrate temperature during deposition has a very strong influence on the phase components of thin films. The results indicate that the direct allowed transitions dominate in the films obtained in this work. For the direct allowed transitions the band gap energy is found to be about 1.98 eV and 2.2 eV. The reflectance of thin bismuth oxide film depends on the substrate. Small transparency of thin films grown on glass is more related to large reflectance than absorption. The reflectance spectra of the bismuth oxide thin films deposited on the Si substrates show higher quality of optical characteristics compared to the samples deposited on glass substrates.

Synthesis and characterization of ZnO thin films deposited via PE-MOCVD

ZnO thin films were deposited on Si(100) and quartz glass substrates via metal organic chemical vapor deposition (MOCVD) using a diethyl zinc (DEZ) precursor and oxygen. The effects of the substrate temperature and direct/indirect plasma enhancement on the growth rate, preferred orientation, and transparency were investigated. From the Arrhenius plot of the deposition rate against the substrate temperature, it was found that the activation energy of the surface reaction was 38.35 kJ/mol. Below 300 °C, amorphous films were obtained, while ZnO films deposited above 300 °C showed a very strong preference for (002) plane orientation. The optical transparency of the films deposited at various experimental conditions showed good quality above 85%, and the bandgap of the films decreased with the substrate temperature in the range of 3.93–4.14 eV. It is assumed that mild energetic reactive radicals in the indirect plasma region are more effective for the MOCVD process than highly energetic ionic particles in the direct plasma region.

Fabrication of transparent, flexible and conductive films using as-grown few-walled carbon nanotubes

We demonstrate the fabrication of transparent, flexible, and conductive (TFC) films using as-grown few-walled CNTs (FCNTs). We used a chemical vapor deposition method with acetylene gas as a feedstock and optimized the growth conditions to obtain thin diameter (<10 nm), ultralong (>1 mm), high quality FCNTs. After a simple ultrasonication, we obtained uniformly dispersed FCNTs in suspension and spraycoated them onto various substrates, such as Si wafers, glass, and transparent and flexible polymeric sheets. We mainly focused on varying the sheet resistance and transmittance as a function of the FCNTs film thickness and found that the minimum film thickness to exhibit appropriate functionality was 60 nm. The obtained sheet resistance of the TFC films on the polymeric substrates reached about 16 kΩ/sq., which is lower than that found in previous reports.