Corning Glass Research Articles

Fabrication, crystallographic and magnetic properties of SrM perpendicular films on Au nano-dot arrays

Abstract Strontium ferrite (SrM) thin films on Au nano-dots were deposited on single-crystal sapphire with (0 0 l ) orientation (Al 2 O 3 (0 0 l )), single crystal MgO with (1 1 1) orientation (MgO (1 1 1)) and Corning glass by employing dc magnetron sputtering system. In order to improve the crystalline orientation for Au nano-dots, an attempt to use the single crystal as the substrate has been carried out. The effects of the substrates and underlayer on grain orientation, magnetic properties, and microstructure of SrM thin films were studied. The SrM grows with its c -axis oriented perpendicularly to the film. The maximum of coercivity and remanent squareness ratio in perpendicular direction for single crystal Al 2 O 3 (0 0 l ) substrate is 3.0 kOe and 0.51, respectively. It is found that the magnetic interaction between SrM grains deposited on Au nano-dots is less than that for the continuous film.

Thermochromic nanocrystalline Au–VO 2 composite thin films prepared by radiofrequency inverted cylindrical magnetron sputtering

Highly crystalline Au–VO 2 nanocomposite thin films were prepared on Corning glass substrates by reactive radiofrequency inverted cylindrical magnetron sputtering (ICMS). It is a low cost potential coating technology for the production of large area uniform nanocomposite thin films exhibiting plasmonic properties. This paper reports the synthesis and feasibility of reliably reproduced high quality of Au–VO 2 by ICMS. Structural, morphological, interfacial analysis and optical properties of synthesized Au–VO 2 nanocomposite thin films are reported.

Electrical and optical properties of copper and nickel molecular materials with tetrabenzo [b,f,j,n] [1,5,9,13] tetraazacyclohexadecine thin films grown by the vacuum thermal evaporation technique

Semiconducting molecular-material thin-films of tetrabenzo (b,f,j,n) [1,5,9,13] tetraazacyclohexadecine copper(II) and nickel(II) bisanthraflavates have been prepared by using vacuum thermal evaporation on Corning glass substrates and crystalline silicon wafers. The films thus obtained were characterized by infrared spectroscopy (FTIR), atomic force microscopy (AFM), ultraviolet-visible (UV-vis) spectroscopy and ellipsometry. IR spectroscopy showed that the molecular-material thin-films exhibit the same intra-molecular bonds as the original compounds, which suggests that the thermal evaporation process does not significantly alter their bonds. The optical band-gap values calculated from the absorption coefficient may be related to non-direct electronic interband transitions. The effect of temperature on conductivity was also measured in these samples. It was found that the temperature-dependent electric current is always higher for the nickel-based material and suggests a semiconductor-like behavior with conductivities in the order of 10(-8)Omega(-1)cm(-1).

The effect of annealing on Al-doped ZnO films deposited by RF magnetron sputtering method for transparent electrodes

In this study, transparent conducting Al-doped zinc oxide (AZO) films with a thickness of 150 nm were prepared on Corning glass substrates by the RF magnetron sputtering with using a ZnO:Al (Al 2O 3: 2 wt.%) target at room temperature. This study investigated the effects of the post-annealing temperature and the annealing ambient on the structural, electrical and optical properties of the AZO films. The films were annealed at temperatures ranging from 300 to 500 °C in steps of 100 °C by using rapid thermal annealing equipment in oxygen. The thicknesses of the films were observed by field emission scanning electron microscopy (FE-SEM); their grain size was calculated from the X-ray diffraction (XRD) spectra using the Scherrer equation. XRD measurements showed the AZO films to be crystallized with strong (002) orientation as substrate temperature increases over 300 °C. Their electrical properties were investigated by using the Hall measurement and their transmittance was measured by UV–vis spectrometry. The AZO film annealed at the 500 °C in oxygen showed an electrical resistivity of 2.24 × 10 − 3 Ω cm and a very high transmittance of 93.5% which were decreased about one order and increased about 9.4%, respectively, compared with as-deposited AZO film.

From amorphous to microcrystalline silicon: Moving from one to the other by halogenated silicon plasma chemistry

Amorphous and microcrystalline silicon thin-films have been deposited on a large variety of substrates including crystalline silicon, Corning glass and polyimide, exploiting SiF4–H2–He radiofrequency (13.56 MHz) plasma-enhanced chemical vapor deposition. Spectroscopic ellipsometry has been mainly applied to investigate the optical and structural characteristics of the deposited films and to investigate the microstructure depending on experimental parameters, such as H2 and He dilution of plasmas, deposition temperature and substrate plasma treatment prior to deposition. Film growth dynamics have also been investigated by analyzing films with different thicknesses. The peculiarities of the SiF4 chemistry involved in heterogeneous processes during film deposition, and responsible for the amorphous to microcrystalline transition are presented. It is demonstrated that the SiF4-H2 chemistry leads to tailoring of film microstructure from amorphous to fully and dense microcrystalline silicon films without any amorphous incubation layer at temperatures as low as 100°C on any substrate, including Corning glass 7059 and polyimide, independently of film thickness. These results and peculiarities of SiF4-based plasmas are discussed within the framework of the literature debate on SiH4 versus SiF4 as silicon precursor.

Growth of c-axis oriented ZnO nanowires from aqueous solution: The decisive role of a seed layer for controlling the wires’ diameter

ZnO nanowires were grown from an aqueous solution at low temperature (95 °C) on Corning glass and silicon (1 0 0) substrates. It turns out that the deposition of a thin ZnO seed layer on the substrates prior to the chemical growth is crucial for obtaining c-axis oriented ZnO nanowires with controllable dimensions. The nanowires’ diameter increases with the grain size of the ZnO seed layer. On the other hand, aqueous solution growth on bare substrates leads to the formation of flowerlike nanostructures, consisting of nanorods, with no preferred growth orientation. The dimensions and morphology of these complex nanostructures depend mainly on growth time. Furthermore, the complex ZnO nanostructures do not show high transmittance, while the nanowires are highly transparent in the visible part of the spectrum.

Effect of Doping on the Optical and Structural Properties of ZnO Thin Films Prepared by RF Diode Sputtering

Nitrogen-doped zinc oxide thin films (ZnO:N), and aluminum-nitrogen co-doped zinc oxide thin films (ZnO:Al:N), were deposited on Corning glass substrates by RF diode sputtering. The nitrogen (N2) content in the working gas varied from 0 to 100 %. XRD patterns revealed improving of the crystalline structure and stronger expressed c-axis preferential orientation of the aluminum-nitrogen co-doped films compared to nitrogen-doped films. The estimated crystallite size varied from 140 to 8 nm, depending on the N2 content. The transmittance spectra of ZnO:N and ZnO:Al:N films were acquired over the wavelength range of 200 < λ < 1000 nm. All nitrogen-doped and Al-N2 co-doped films were colored as a result of the increase absorption near the band edge. Optical band gap (Eg) of the ZnO:N and ZnO:Al:N thin films decreases with increase of the N2 content in the working gas.

HER2 Carboxyl-terminal Fragments Regulate Cell Migration and Cortactin Phosphorylation

A group of breast cancer patients with a higher probability of developing metastasis expresses a series of carboxyl-terminal fragments (CTFs) of the tyrosine kinase receptor HER2. One of these fragments, 611-CTF, is a hyperactive form of HER2 that constitutively establishes homodimers maintained by disulfide bonds, making it an excellent model to study overactivation of HER2 during tumor progression and metastasis. Here we show that expression of 611-CTF increases cell motility in a variety of assays. Since cell motility is frequently regulated by phosphorylation/dephosphorylation, we looked for phosphoproteins mediating the effect of 611-CTF using two alternative proteomic approaches, stable isotope labeling with amino acids in cell culture and difference gel electrophoresis, and found that the latter is particularly well suited to detect changes in multiphosphorylated proteins. The difference gel electrophoresis screening identified cortactin, a cytoskeleton-binding protein involved in the regulation of cell migration, as a phosphoprotein probably regulated by 611-CTF. This result was validated by characterizing cortactin in cells expressing this HER2 fragment. Finally, we showed that the knockdown of cortactin impairs 611-CTF-induced cell migration. These results suggest that cortactin is a target of 611-CTF involved in the regulation of cell migration and, thus, in the metastatic behavior of breast tumors expressing this CTF.

Some Methodic Aspects in Optimizing the Radioimmunoassay of β-Endorphin

A specific double antibody radioimmunoassay (RIA) for human beta-endorphin (beta-EP) using an antibody to synthetic beta h-endrophin was established. This antibody cross-reacted with beta-Lipotropin (beta-LPH) at 42 per cent on molar basis and allowed a usable range of 20 pg to 4 ng of beta-endorphin per ml in the assay. Comparing the efficiency of the conventional extraction procedures under various conditions using Corning glass, Vycor glass, QUSO G-32, silicic acid and controlled pore glass 75, the optimal result was obtained by Corning glass, with a recovery rate of more than 80 per cent. The most simple and rapid method with an extraction efficiency of more than 90 per cent was found to be the extraction by use of Sep-Pak C18 cartridges. The separation of beta-endorphin from beta-LPH was studied using Sephadex G-50, G-75, G-100 and Bio-Gel P-60 columns and different elution media. The use of a Sephadex G-50 column (0.9 X 55 cm) and elution with 0.1 N acetic acid-0.05 per cent HSA gave the best result. The reliability of the radioimmunoassay was shown under physiological and pathophysiological conditions.

Structural, electrical, and optical properties of antimony-doped tin oxide films prepared at room temperature by radio frequency magnetron sputtering for transparent electrodes

Antimony-doped tin oxide (ATO) films were prepared on 7059 Corning glass substrate by the radio frequency (rf) magnetron sputtering method using SnO2 target mixed with Sb of 6 wt % at room temperature. The working pressure was varied from 0.67 to 2 Pa in steps of 0.67 Pa, and the rf power was varied from 100 to 175 W in steps of 25 W at room temperature. The thickness of the deposited ATO films was about 150 nm. X-ray diffraction (XRD) measurements showed the ATO films to be crystallized with a strong (101) preferred orientation as the rf power is increased. The spectra revealed that the deposited films were polycrystalline, retaining the tetragonal structure. The grain size was estimated from the XRD spectra using the Scherrer equation and found to decrease with a decrease in the working pressure and an increase in the rf power, while the surface roughness was observed to be smoothened. The ATO film that was deposited at a working pressure of 0.67 Pa with rf power of 175 W showed the lowest resistivity of 8.6×10−3 Ω cm, and the optical transmittance was 86.5% in the visible wavelength range from 400 to 800 nm.

Structural changes studies of a-Si:H films deposited by PECVD under different hydrogen dilutions using various experimental techniques

Plasma enhanced chemical vapour deposition (PECVD) has been used to prepare hydrogenated amorphous silicon (a-Si:H) thin films at different hydrogen dilution of silane source gas. The films were deposited on Corning glass 1737 substrate and on (100) oriented c-Si wafers and characterized by XRD diffraction, micro-Raman and FTIR spectrometry. Experimental data show evolution from amorphous to nanocrystalline silicon and contain the medium-range order (MRO) with varying hydrogen dilution during deposition. From X-ray diffraction and Raman analysis, it is found that the presence of crystalline phase depends on the kind of substrate and on the dilution scale.

Thickness dependent physical properties of close space evaporated In 2S 3 films

In recent years, In 2S 3 is considered as a promising buffer layer in the fabrication of heterojunction solar cells. Film thickness is one of the important parameters that alters the physical characteristics of the grown layers significantly. The effect of film thickness on the structural, morphological, optical and electrical properties of close space evaporated In 2S 3 layers has been studied. In 2S 3 thin films with different thicknesses in the range, 100–700 nm were deposited on Corning glass substrates at a constant substrate temperature of 300 °C. The films were polycrystalline exhibiting strong crystallographic orientation along the (103) plane. The deposited films showed mixed phases of both cubic and tetragonal structures up to a thickness of 300 nm. On further increasing the film thickness, the layers showed only tetragonal phase. With increase of film thickness, both the crystallite size and surface roughness in the films were found to be increased. The optical constants such as refractive index and extinction coefficient of the as-grown layers have been calculated from the optical transmittance data in the wavelength range, 300–2500 nm. The optical transmittance of the films was decreased from 82% to 64% and the band gap varied in the range, 2.65–2.31 eV with increase of film thickness. The electrical resistivity as well as the activation energy was evaluated and found to decrease with film thickness. The detailed study of these results was presented and discussed.

Deposition of low-resistivity gallium-doped zinc oxide films by low-temperature radio-frequency magnetron sputtering

The transparent and conductive gallium-doped zinc oxide (GZO) film was deposited on 1737F Corning glass using the radio-frequency (RF) magnetron sputtering system with a GZO ceramic target. (The Ga 2O 3 contents are approximately 5 wt. %). In this study, the effect of the sputtering pressure on the structural, optical and electrical properties of GZO films upon the glass or polyester film (PET) substrate was investigated and discussed in detail. The GZO film was grown under a steady RF power of 400 W and a lower substrate temperature from room temperature up to 200 °C. The crystal structure and orientation of GZO thin films were examined by X-ray diffraction. All of the GZO films under various sputtering pressures had strong c-axis (002)-preferred orientation. Optical transparency was high (> 80%) over a wide spectral range from 380 nm to 900 nm. According to the experimental data, the resistivity of a single-layered GZO film was optimized at ∼ 8.3 × 10 − 4 Ω cm and significantly influenced by the sputtering pressure. In further research, the sandwich structure of the GZO film/Au metal/GZO film was demonstrated to improve the electrical properties of the single-layered GZO film. The resistivity of the sandwich-structured GZO film was around 2.8 × 10 − 4 Ω cm.

Preparation and optical and electrical evaluation of bulk SiO 2 sonogel hybrid composites and vacuum thermal evaporated thin films prepared from molecular materials derived from (Fe, Co) metallic phthalocyanines and 1,8 dihydroxiantraquinone compounds

Semiconducting molecular material of PcFe(CN)L1 and PcCo(CN)L1 (L1 = 1,8 dihydroxianthraquinone), PcFe(CN)L2 and PcCo(CN)L2 (L2 = double potassium salt of 1,8 dihydroxianthraquinone) have been successfully used to prepare thin film and bulk sol–gel hybrid optical materials. These samples were developed according to the vacuum thermal evaporation technique and the catalyst-free sonogel route, respectively. Thin films samples were deposited on Corning glass substrates and crystalline silicon wafers and were characterized by infrared (FTIR), Raman and ultraviolet-visible (UV–vis) spectroscopies. IR-spectroscopy and Raman studies unambiguously confirmed that the molecular material thin films exhibit the same intra-molecular bonds, which suggests that the thermal evaporation process does not alter these bonds significantly. These results show that it is possible to deposit molecular materials of PcFe(CN)L2 and PcCo(CN)L2 on Corning glass substrates and silicon wafers. From the UV–vis studies the optical band gap ( E g) was evaluated. The effect of temperature on conductivity was also evaluated in these samples. Finally, the studied molecular systems dissolved at different concentrations in tetrahydrofuran (THF) were successfully embedded into a highly pure SiO 2 sonogel network generated via sonochemical reactions to form several solid state, optically active sol–gel hybrid glasses. By this method, homogeneous and stable hybrid monoliths suitable for optical characterization can be produced. The linear optical properties of these amorphous bulk structures were determined by the Brewster angle method and by absorption-, Raman- and photoluminescent (PL)-spectroscopies, respectively.

Structural defects caused by a rough substrate and their influence on the performance of hydrogenated nano-crystalline silicon n–i–p solar cells

We present a cross-sectional transmission electron microscopy study of a set of hydrogenated nano-crystalline silicon n–i–p solar cells deposited by hot-wire chemical vapour deposition on Corning glass substrates coated with ZnO-covered Ag layers with various surface roughnesses. Strip-like structural defects (voids and low-density areas) are observed in the silicon layers originating from micro-valleys of Ag grains. A correlation between the opening angles of the textured surface and the appearance of these strips was found. We propose that in order to grow high-quality hydrogenated nano-crystalline silicon absorber layers for solar cell applications, the morphology of the Ag surface is a critical property, and the micro-valleys at the ZnO surface with an opening angle smaller than around 110° should be avoided.

Guided growth of in-plane lateral SiNWs led by indium catalysts

AbstractHere we report a new in-plane solid-liquid-solid (IPSLS) mode for obtaining in-plane silicon nanowires (SiNW), which can be controlled and directly guided into various desired patterns for circuit architecture. Indium catalyst drops are firstly formed by a H2 plasma reduction of a thin layer of ITO on Corning glass substrate and then covered by an a-Si:H layer deposited at low temperature (100oC-200oC). The growth of SiNWs is activated in a reacting-gas-free thermal annealing process and led by the indium catalyst drops, that absorb and transform the a-Si:H matrix into crystalline SiNWs behind. At least two guided modes, that is, the a-Si:H channel guided mode and the step edge guided mode, can be applied to effectively control the growth routes for the lateral SiNWs. This guided growth of the IPSLS SiNWs lays an important basis for realizing various SiNWs-based device applications directly on top of low-cost substrates.

One pot direct hydrothermal growth of photoactive TiO 2 films on glass

We demonstrate that titanium (IV) oxide films may be deposited on Corning glass by a simple, one-pot, low temperature (95 °C) hydrothermal growth technique and that providing the correct conditions are employed, the films produced show clear photoactivity under UV illumination as evidenced by changes in water contact angle and the progressive photo-oxidation of stearic acid. It is further demonstrated that the growth, structure and photoactivity of the films depends critically upon the H 2O concentration employed during growth. For H 2O concentrations below 0.1 M, little or no growth was observed, while above 0.3 M, precipitation or even gelation rapidly occurred. Only at H 2O concentrations of 0.1 M and 0.2 M was appreciable film growth observed, while photoactive titania was formed only via growth using a water concentration of 0.1 M, the films grown using the higher concentration of water (0.2 M) being essentially photo-inactive. The method developed is discussed in terms of the possible chemical steps involved and is proposed as a low-cost alternative to higher temperature, less environmentally friendly approaches to TiO 2 film production.

Influence of thickness and growth temperature on the optical and electrical properties of ZnO thin films

Zinc oxide transparent conductive thin films were prepared using the pulsed laser deposition technique onto Corning glass substrates and the dependences of their optical and electrical properties on the thickness and the growth temperature were investigated. As shown, the films present 90% average transmittance, their energy gap position depending on the film thickness and the growth temperature. An additional absorption band was also observed near 3.44 eV, the position of its maximum also depending on the growth parameters. Finally, the electrical properties of the films were found to be affected mainly by the growth temperature and less by the thickness.

Microstructure and magnetic properties of Ag/FePt double layer films with different cooling processes

Ag/FePt double layer films with different Ag thicknesses were deposited on Corning glass substrates by RF magnetron sputtering and L10-FePt films were prepared after the as-deposited samples were subjected to vacuum annealing with different cooling processes. Experimental results show that the thickness of the Ag layer is a very important factor in preparing the film with a high perpendicular anisotropy. The 40 nm Ag/15 nm FePt film exhibits a high perpendicular coercivity of 9053 Oe and a low in-plane coercivity of 6059 Oe. The Ag/FePt double layer films with natural cooling have larger Mr/Ms values than those with fast cooling processes. The angular dependence of the coercivity profile for the FePt film with a thickness of 15 nm shows a typical domain wall motion behavior, while both the simulated curve of FePt film of 15 nm and the one of 40 nm Ag/15 nm FePt double layer film revealed the rotation mode, which indicates that the grains are weakly coupled and their reversals of magnetizations are independent in the 40 nm Ag/15 nm FePt film.

Iron-mediated Aggregation and a Localized Structural Change Characterize Ferritin from a Mutant Light Chain Polypeptide That Causes Neurodegeneration

Nucleotide insertions in the ferritin light chain (FTL) polypeptide gene cause hereditary ferritinopathy, a neurodegenerative disease characterized by abnormal accumulation of ferritin and iron in the central nervous system. Here we describe for the first time the protein structure and iron storage function of the FTL mutant p.Phe167SerfsX26 (MT-FTL), which has a C terminus altered in sequence and extended in length. MT-FTL polypeptides assembled spontaneously into soluble, spherical 24-mers that were ultrastructurally indistinguishable from those of the wild type. Far-UV CD showed a decrease in α-helical content, and 8-anilino-1-naphthalenesulfonate fluorescence revealed the appearance of hydrophobic binding sites. Near-UV CD and proteolysis studies suggested little or no structural alteration outside of the C-terminal region. In contrast to wild type, MT-FTL homopolymers precipitated at much lower iron loading, had a diminished capacity to incorporate iron, and were less thermostable. However, precipitation was significantly reversed by addition of iron chelators both in vitro and in vivo. Our results reveal substantial protein conformational changes localized at the 4-fold pore of MT-FTL homopolymers and imply that the C terminus of the MT-FTL polypeptide plays an important role in ferritin solubility, stability, and iron management. We propose that the protrusion of some portion of the C terminus above the spherical shell allows it to cross-link with other mutant polypeptides through iron bridging, leading to enhanced mutant precipitation by iron. Our data suggest that hereditary ferritinopathy pathogenesis is likely to result from a combination of reduction in iron storage function and enhanced toxicity associated with iron-induced ferritin aggregates.