Showing papers on "Indium tin oxide published in 1994"

Electrically conducting polymers can noninvasively control the shape and growth of mammalian cells.

Abstract: Electrically conducting polymers are novel in that their surface properties, including charge density and wettability, can be reversibly changed with an applied electrical potential. Such properties might render conducting polymers unique for biological applications. However, the majority of research on conducting polymers has been carried out under nonbiological conditions. We synthesized optically transparent polypyrrole thin films and studied them in environments suitable for protein adsorption and mammalian cell culture. In vitro studies demonstrated that extracellular matrix molecules, such as fibronectin, adsorb efficiently onto polypyrrole thin films and support cell attachment under serum-free conditions. When aortic endothelial cells were cultured on fibronectin-coated polypyrrole (oxidized) in either chemically defined medium or the presence of serum, cells spread normally and synthesized DNA. In contrast, when the polymer was switched to its neutral state by applying an electrical potential, both cell extension and DNA synthesis were inhibited without affecting cell viability. Application of a similar electrical potential to cells cultured on indium tin oxide surfaces had no effect on cell shape or function. These data suggest that electrically conducting polymers may represent a type of culture substrate which could provide a noninvasive means to control the shape and function of adherent cells, independent of any medium alteration.

New ultraviolet‐transport electroconductive oxide, ZnGa2O4 spinel

Abstract: ZnGa2O4 having the spinel structure was prepared, and optical and electrical properties of the material were measured. By the measurements of diffuse reflectance spectra, ZnGa2O4 was found to have a wider band gap (∼5 eV) than ITO (indium tin oxide). Electrical conductivity of the H2‐annealed ceramic of ZnGa2O4 was 3×101 S cm−1. Thus the ZnGa2O4 spinel was found to be a new UV‐transparent electronic conductor.

Transparent conducting thin films of GaInO3

Abstract: GaInO3 is recently identified transparent conducting material which is structurally and chemically distinct from indium tin oxide [R. J. Cava, J. M. Phillips, J. Kwo, G. A. Thomas, R. B. van Dover, S. A. Carter, J. J. Krajewski, W. F. Peck, Jr., J. H. Marshall, and D. H. Rapkine, Appl. Phys. Lett. 64, 2071 (1994)]. We have used both dc reactive sputtering in the on‐ and off‐axis geometries and pulsed laser deposition to grow films of this material. Layers of pure GaInO3 as well as those partially substituted with Ge for Ga or Sn for In have been studied. Both growth techniques are capable of producing films with conductivity ∼400 (Ω cm)−1 and transmission as high as 90% throughout the visible spectrum for ∼1‐μm‐thick films. The growth techniques differ in the morphology of the films produced as well as in the degree of dopant incorporation that can be achieved. A post‐growth anneal in H2 can help produce an optimized oxygen content and a reduction of resistivity. Hall measurements indicate a carrier conce...

Ferroelectric integrated circuit

Abstract: An oversize ferroelectric capacitor is located against the contact hole to the MOSFET source/drain in a DRAM. A barrier layer made of titanium nitride, titanium tungsten, tantalum, titanium, tungsten, molybdenum, chromium, indium tin oxide, tin dioxide, ruthenium oxide, silicon, silicide, or polycide lies between the ferroelectric layer and the source drain. The barrier layer may act as the bottom electrode of the ferroelectric capacitor, or a separate bottom electrode made of platinum may be used. In another embodiment in which the barrier layer forms the bottom electrode, an oxide layer less than 5 nm thick is located between the barrier layer and the ferroelectric layer and the barrier layer is made of silicon, silicide, or polycide. A thin silicide layer forms and ohmic contact between the barrier layer and the source/drain. The capacitor and the barrier layer are patterned in a single mask step. The ends of the capacitor are stepped or tapered. In another embodiment both the bottom and top electrode may be made of silicon, silicide, polycide or a conductive oxide, such as indium tin oxide, tin dioxide, or ruthenium oxide.

GaInO3: A new transparent conducting oxide

Abstract: GaInO3, a layered material with the β Ga2O3 crystal structure, can be doped with electrons through the introduction of oxygen deficiency, Sn doping for In, or Ge doping for Ga. At atomic doping levels of 10% or less, resistivities as low as 3 mΩ cm are obtained. In contrast to polycrystalline indium tin oxide (ITO), which is distinctly green, conductive gallium indium oxide is light grey with no visible coloration. Thin films of doped GaInO3 display good transparency over the whole optical window, superior to that of ITO in the green‐blue region.

Blue electroluminescence from porous silicon carbide

Abstract: The possibility of a new blue light emitting diode (LED) using porous SiC as a luminescent material is described The porous SiC is electrochemically formed on a single crystalline 6H‐SiC substrate fabricated by the Acheson method The diode structure is a Schottky‐like junction between indium tin oxide (ITO) and porous SiC The ITO/porous SiC junction shows a rectification behavior and a blue electroluminescence (EL) under the forward direction

Postdeposition Annealing Influence on Sputtered Indium Tin Oxide Film Characteristics

Abstract: The influence of postdeposition annealing on sputtered indium tin oxide (ITO) film characteristics were investigated. The annealing experiments were carried out in air or vacuum atmosphere. Both air and vacuum annealing decreased the resistivity up to heat treatment of 200° C. Over 300° C treatment, air annealing increased resistivity whereas vacuum annealing decreased it. It was clarified that the resistivity depended on the carrier concentration. The lowest resistivity attained was 1.3×10-4 Ωcm, with film deposited on a 250° C heated substrate and annealed in vacuum atmosphere at 300° C. Transmittance was improved in both air and vacuum annealing. In air and vacuum annealing, crystallinity improved with increasing annealing temperature. The surface topography showed no changes with air or vacuum annealing.

Maskless patterning of indium tin oxide layer for flat panel displays by diode‐pumped Nd:YLF laser irradiation

Abstract: An indium tin oxide (ITO) layer on a lime glass substrate for flat panel displays has been patterned without a mask by scanning Nd:YLF (neodymium‐doped yttrium‐lithium‐fluoride) laser irradiation in a pulsed mode. Both fundamental and frequency doubled lines of 1.047 μm and 523.5 nm were compared for processing. SEM (scanning electron microscopy) and surface stylus observation revealed that only the top ITO layer could be removed without substrate etching. A finer patterning was possible for irradiation of a 523.5 nm line because of the better focusing feature, though higher laser energy density was required for this line than for a 1.047 μm line because of the lower light absorption.

Structural and electrical properties of rf magnetron‐sputtered Ba1−xSrxTiO3 thin films on indium‐tin‐oxide‐coated glass substrate

Abstract: Structural and electrical properties of rf magnetron‐sputtered Ba1−xSrxTiO3 thin films (x=0, 025, 05, 075, 1) on indium‐tin‐oxide‐coated glass substrate were studied The dense Ba1−xSrxTiO3 thin films sputtered from five different targets at the deposition temperature of 550 °C had individual orientations The results of compositional analysis in films showed the deviation from the stoichiometry [(Ba+Sr)/Ti=1009−1089] with the increase of SrTiO3 content in the targets The tetragonality in crystallographic structure of Ba1−xSrxTiO3 thin films was not observed even in the case of

Deposition of Indium Tin Oxide Films on Acrylic Substrates by Radiofrequency Magnetron Sputtering

Abstract: Indium tin oxide (ITO) films were deposited onto acrylic substrates by rf magnetron sputtering. Low substrate temperature (<80°C) and low rf power (<28 W) were maintained during sputtering to prevent acrylic substrate deformation. The influence of sputtering parameters, such as rf power, target-to-substrate distance, and chamber pressure, on the film deposition rate, the electrical properties, as well as the optical properties of the deposited films was investigated. Both the refractive index and the extinction coefficient were derived. The high reflection at wavelengths greater than 3 μ made these sputtered ITO films applicable to infrared mirrors.

Fabrication of carbon dioxide gas sensor and its alarm system using indium tin oxide (ITO) thin films

Abstract: Indium tin oxide (ITO) polycrystalline thin films grown on alumina substrates by thermal evaporation, followed by annealing in a humid environment, are used for fabricating a gas sensor to detect carbon dioxide (CO 2 ) gas produced by incomplete burning in domestic combustion equipment and combustion processes. ITO thin-film gas sensors with a thickness of about 150 nm show a maximum sensitivity when operated at a temperature of 573 K for various concentrations of CO 2 gas. A tentative mechanism based on molecular orbital (MO) theory is proposed for the role of CO 2 gas in increasing the conductance of ITO thin-film gas sensors. This increase in conductance is utilized to initiate the triggering of an electronic alarm system.

Highly reliable operation of indium tin oxide AlGaInP orange light-emitting diodes

Abstract: Indium-tin oxide (ITO) transparent conducting films with a low resistivity of 2–3 × 10-4 Ω·cm have been introduced as a window layer in (Al0.7Ga0.7)0.5In0.5P/(Al0.1Ga0.9)0.5In0.5P double-heterostructure orange light-emitting diodes to obtain a uniform spatial distribution of the emission light, a good device performance and high reliability. An output power of 450 µW at 20 mA corresponding to an external quantum efficiency of 1.1% for the 620 nm emission can be achieved.

Optically transparent indium-tin-oxide (ITO) ohmic contacts in the fabrication of vertical-cavity surface-emitting lasers

Abstract: The authors report what they believe to be the first successful fabrication of an InGaAs/GaAs vertical-cavity surface emitting laser (VCSEL) using optically transparent indium-tin-oxide (ITO) ohmic contacts to p- and n-type regions of the laser. Threshold current densities J/sub th/ are similar to those lasers fabricated from the same wafer using conventional ohmic contacts.

Performance of electrochromic cells of polyaniline in polymeric electrolytes

Abstract: Polyaniline is currently considered to have good device potential [1-5]. One of the devices for which polyaniline is seriously considered is the electrochromic display. A number of studies on the electrochromism (EC) of polyaniline covering various aspects, such as the mechanism of the colour change [6-8] and the effect of cell parameters on the switching time [9], have been done, but these and similar studies have generally been conducted in liquid media in electrochemical cells. In practical devices it is preferable to employ solid materials in order to minimize the problems of sealing in hazardous liquids. Furthermore, EC devices are usually required to have a thin layer configuration. With these considerations in mind, we have performed experiments with thin layer cells of polyaniline containing a supporting electrolyte such as LiC10 4 dissolved in polyethylene oxide (PEO) or polyvinyl alcohol (PVA). We have also studied cells containing urea dissolved in glycerol as the medium. We report the performance of such cells in this letter. A polymeric electrolyte such as PEO was chosen because the amorphous nature of PEO leads to good ionic conductivity and redox stability up to +3 V [10]. In addition, the combination of PEO/ LiC104 is known to be a very fast ionic conductor, with the Li ÷ being the mobile species [11]. Recently, reports have also appeared which describe solid state electrochromic cells of methylene blue using polyacrylamide [12] and gels of polymethyl methacrylate in electrochromic cells of WO3 [13]. The composition of the electrochromic cells used in this study is given in Table I. We have studied the effects of the medium on the various parameters such as switching time, cycle lifetime and applied voltage on the electrochromic display. The current transients for the switching reaction of polyaniline were analysed to understand the influence of mass transport on the switching reaction in polyaniline. Cells for electrochromic studies were constructed as follows. Polyaniline (nominal thickness 1 #m) was coated with indium tin oxide (ITO) plate by application of alternating voltage ( -0 .1 V to 1 V) in HC1 medium containing 0.1 M aniline. The film was dried and dip coated with the appropriate electrolyte then covered with another plate of ITO. The whole assembly was then sealed with wax to exclude air. The schematic of such an electrochromic cell is shown in Fig. 1. Electrical contacts were made using alligator clips after ensuring that there was minimal contact resistance. The cell was mounted on a stand in an optical bench and illuminated at 632 nm with a tungsten-halogen lamp (Oriel Corp., USA) through a monochromator (Oriel). The transmitted light was monitored by an Si photodiode (Oriel). The diode

Energetic particles in the sputtering of an indium–tin oxide target

Abstract: Energetic negative ions and neutral atoms were simultaneously observed using a time‐of‐flight apparatus during indium–tin oxide (ITO) film preparation by conventional planar magnetron sputtering of an ITO target. The sputtering was performed in pure Ar gas and compared with ZnO: Al sputtering. Energetic particles such as O− and O−2 ions and neutral O atoms were detected in the time‐of‐flight spectra, although the flux intensity of these particles was much less than that found in the ZnO sputtering. It was also found that other particles exist at the same time, which were thought to be reflected Ar atoms or O−3 ions from the target surface. However, the flux intensity of these particles was found to be less than that of the energetic O− ions and O atoms. The strong energetic particles, which primarily bombarded the substrate during the ITO sputtering were found to be energetic O− ions and O atoms.

Preparation of ITO Thin Films by Sol-Gel Method

Abstract: ITO thin films were prepared at 550°C by a sol-gel method using colloidal particles derived from a solution of indium nitrate and tin chloride. The colloidal particles were secondary particles with about 50nm in diameter and were dispersed by adding indium chloride as a peptizer to prepare a dipping solution. Firing of gel films at 550°C for 2min developed a film microstructure consisting of ITO particles through thermal decomposition of the colloidal particles. Indium chloride was also decomposed to form indium oxide by firing, and the oxide was found to crosslink the ITO particles in the film. ITO films with thickness up to 2μm were obtained by a single dipping-firing procedure. The sheet resistivity of the films prepared at 550°C for 30min was 500Ω/cm2 and the optical transmittance was above 90% in the visible region.

Dependence of Photovoltages of Spray‐Deposited Indium Tin Oxide/Silicon Oxide/Silicon Junction Solar Cells on Spray Solvents

Abstract: The photovoltages of spray-deposited indium tin oxide/silicon oxide/n-Si junction solar cells are found to depend strongly on the spray solvents such as methanol, ethanol, ethyl acetate, water, etc. It is also found that the work function of the indium tin oxide (ITO) films is dependent on the spray solvents, and the higher the work function of the ITO films, the larger the photovoltage. X-ray photoelectron spectroscopy (XPS) measurements indicate that an In-OH species, probably formed by reactions of the ITO film with the spray solvents, is present in the deposited film in cases where its work function is high. The resistivity of the ITO films produced using the organic spray solvents is in the range of 2 [approximately] 4 [times] 10[sup [minus]4] [Omega] cm, leading to high fill factors of the solar cells, while that of the films deposited using water as a spray solvent is as high as 1.2 [times] 10[sup [minus]3] [Omega] cm, resulting in low fill factors. On the basis of the XPS measurements, the high resistivity of the latter ITO films is attributed to a small amount o tin ions in the films. X-ray diffraction measurements show that the crystal orientation of the ITO films alsomore » depends on the spray solvents, indicating that the film formation mechanism varies with the spray solvents. By use of a mixed solvent of methanol:ethyl acetate:water = 5:5:1, the photovoltage becomes the highest, and the conversion efficiency of 14% is achieved.« less

Effects of seeding layer on perovskite transformation, microstructure and transmittance of sol-gel-processed lanthanum-modified lead zirconate titanate films

Abstract: A series of sol-gel-processed lanthanum-modified lead zirconate titanate (PLZT) thin films with La/Zr/Ti ratios of 8.5/65/35, 9/65/35, 9.5/65/35, 15.5/40/60 and 18/30/70 were prepared on indium tin oxide (ITO)-coated Corning 7059 glass substrates and heat-treated at different temperatures from 475° C to 685° C. The X-ray diffraction, microstructure, optical transmittance spectra and the polarization vs electric field curves were investigated. The P(L)ZT thin films of higher Ti/Zr ratio show lower transformation (from pyrochlore to perovskite) temperature. The PLZT(8.5–9.5/65/35) thin film with the seeding layer shows improved phase content, high optical transmittance and enhanced perovskite transformation kinetics. The grain sizes are reduced (from 5–6 µ m to 0.1–0.2 µ m) and uniform. The fracture surfaces of the films with a seeding layer consist of columnar structure of which the grains grew from the seeding layer. The optical transmittance is enhanced, and the polarization value at 400 KV/cm increases for the film with the seeding layer.

Photoelectrochemical Investigations on Naphthalocyanine Derivatives in Thin Films

Abstract: Photoelectrochemical properties of Zn-naphthalocyanine (ZnNc) and its modified compound, Zn-2,3-tetraquinoxalinotetraazaporphyrin (ZnTQP) were investigated in thin films. The ZnNc electrode vacuum-deposited on an indium tin oxide (ITO) substrate exhibited almost an ohmic I-V curve in the dark and small cathodic photocurrents under illumination, which was typical for the p-type semiconduction of the ZnNc layer, in a photoelectrochemical cell. The drop-casted film electrode of ZnTQP, on the other hand, showed rectified I-V characteristics in the dark and high anodic photocurrents under illumination, which was attributed to the n-type semiconducting character of the ZnTQP layer. These different photoelectrochemical behaviors were characterized by photocurrent action spectra and ultraviolet photoelectron spectroscopy. The substitution with quinoxalino groups into the Nc macrocyclic system gave rise to lowering of the HOMO energy level for the TQP molecule. This electronic energy shift generated donor electron states in the band gap after contact with the substrate or electrolyte and enabled the photooxidation at the valence band edges corresponding to the Soret-and Q-band excitations. 55 refs., 10 figs.

Photon scanning tunneling microscope in combination with a force microscope

Abstract: The simultaneous operation of a photon scanning tunneling microscope with an atomic force microscope is presented. The use of standard atomic force silicon nitride cantilevers as near-field optical probes offers the possibility to combine the two methods. Vertical forces and torsion are detected simultaneously with the optical near field, which allows a comparison between topography and the optical signal. Images of an optical thin film (indium tin oxide) and a Langmuir-Blodgett layer (pentacosa diynoic acid) show absorption contrast with a lateral resolution of about 30 nm (based o­n edge steepness), which is well below the diffraction limit

Separator for solid electrolyte fuel cell

Abstract: PURPOSE: To provide high density and strength and high electrical conductivity, maintain high resistance against heat and corrosion, allow the adjustment of thermal expansion characteristics such as a coefficient of thermal expansion, restrain the diffusion of chrome as a separator component, or the oxide thereof due to the existence of a protection film to prevent an adverse effect on a cathode, and maintain a high cell performance over a long time. CONSTITUTION: A separator for a solid electrolyte fuel cell is formed out of a separator substrate 14 containing cermet made of a heat resistant metal having an alloy containing 5% or more of chrome and a ceramic material, and a protection film of metallic oxide laid on the gas concordant surface of the cathode 12 of the substrate 14 in such a state as not being in direct contact with cathode gases. In this case, the alloy is preferably a nickel or iron base alloy, and the ceramic material is preferably alumina or a rare earth composite oxide. Furthermore, the metallic oxide is preferably indium oxide, Sn-doped indium oxide, zinc oxide, tin oxide, Sb-doped tin oxide, oxide cobalt, iron oxide or a rare earth composite oxide.

Application of dynamic in situ ellipsometry to the deposition of tin‐doped indium oxide films by reactive direct‐current magnetron sputtering

Abstract: The application of dynamic in situ ellipsometry to the monitoring of the deposition of transparent indium tin oxide layers by reactive direct‐current magnetron sputtering in Ar/O2 gas mixtures is described. The dependence of the refractive index and the deposition rate on the discharge power and on the oxidation state of the target show that the state of the target is the essential parameter for the production of indium tin oxide films with the desired properties. The sputter yield of the pure In:Sn alloy exceeds that of the oxide by a factor of about 6. The film growth species in the case of an oxidized target are In2O molecules or oxide clusters rather than metal atoms.

Effect of internal stress on adhesion and other mechanical properties of evaporated indium tin oxide (ITO) films

Abstract: The relationship between various mechanical properties of evaporated indium tin oxide (ITO) films has been investigated. The hardness and internal stress were found to be correlated. This correlation can be expressed as a linear expression similar to that reported for a bulk material. The strength of adhesion to the substrate was observed to be related to the internal stress. This relationship was also linear and could be well interpreted quantitatively by assuming that the stored elastic energy in ITO films was constant during peeling. The coefficient of kinetic friction was found not to be related to any mechanical property. It depended only on the roughness of the film surfaces. A series of Taber abrasion tests revealed that the coefficient of friction was the most important for mechanical durability among factors such as hardness, adhesion, strength, and coefficient of friction.

Relaxation of Second-Harmonic Generation in Guest/Host Polymers Poled by Indium-Tin Oxide Sandwich Electrodes

Abstract: Second-harmonic generation (SHG) is used to monitor reorientation dynamics of 4-(dimethylamino)-4'-nitrostilbene doped at 1 wt % in poly(ethyl methacrylate) within a temperature range of T g ±30 K. Special emphasis is put on a systematic analysis of experiments conditions and their severe impact on SHG data for samples which are poled in an indium-tin oxide (ITO)-sandwich-electrode configuration. These effects include thermal history, local heating effects due to laser focus, importance of dopant concentration, physical aging, details of the poling procedure, and charge-injection effects. The fast initial response of the SHG signal upon field switching is attributed to space charge effects. We show how the problem of SHG reproducibility can be overcome with appropriate experimental conditions

Visible electroluminescence from stain-etched porous Si diodes

Abstract: Visible electroluminescence (EL) from stain-etched porous silicon (PoSi) films is presented. The PoSi thin layers (/spl sim/200 nm) were obtained by stain-etching of B-doped 6-16 /spl Omega/-cm [100] crystalline Si in a HF:HNO/sub 3/:H/sub 2/O (1:3:5) solution. Indium tin oxide (ITO) films of /spl sim/2500 /spl Aring/ were used to form a Schottky contact. Visible EL was observed at room temperature from the diode under forward bias. EL onset bias as low as 3 mA/cm/sup 2/ was measured. The EL, with an emission peak at /spl sim/640 nm, is similar to the photoluminescence under UV excitation, indicating the same luminescent centers. This result demonstrates a promising and simple technique for the fabrication of PoSi-based light emitting diodes and flat panel display devices. >