Showing papers on "Indium tin oxide published in 1996"

Work function of indium tin oxide transparent conductor measured by photoelectron spectroscopy

Abstract: We used ultraviolet and x‐ray photoelectron spectroscopy (XPS) and (UPS) techniques to directly measure absolute values of vacuum work function of indium tin oxide (ITO) thin films. We obtained a work function of 4.4–4.5 eV which is lower than the commonly cited value. These values do not change substantially by heating and Ar ion sputtering. The atomic concentrations of each element in ITO, measured with XPS, are also quite stable under heat treatment and ion sputtering.

Efficient blue polymer light‐emitting diodes from a series of soluble poly(paraphenylene)s

Abstract: Three derivatives of poly(paraphenylene) (PPP) have been synthesized, all with excellent solubility in common organic solvents. Efficient blue polymer light‐emitting diodes (LEDs) are demonstrated using these PPPs as the semiconducting and luminescent polymers. Double‐layer polymer LEDs (consisting of a hole transport layer in addition to the electroluminescent layer) emit blue light with external quantum efficiencies between 1% and 3% photons per electron, when using indium tin oxide as the anode and calcium as the cathode. Using internal field emission (Fowler–Nordheim tunneling) of single carrier devices for both electrons and holes, the energies of the top of the π band and the bottom of the π* band have been determined as, respectively, 5.7 and 2.3 eV below the vacuum. The operating voltages of these LEDs have been lowered by using a porous polyaniline anode, or by blending PPP with a hole transport material. LEDs using air stable cathodes, silver, indium, aluminum, and copper, were also demonstrated...

Fabrication and properties of light‐emitting diodes based on self‐assembled multilayers of poly(phenylene vinylene)

Abstract: Light‐emitting diodes have been fabricated from self‐assembled multilayers of poly(p‐phenylene vinylene) (PPV) and two different polyanions; polystyrene sulfonic acid (SPS) and polymethacrylic acid (PMA). The type of polyanion used to assemble the multilayer thin films was found to dramatically influence the behavior and performance of devices fabricated with indium tin oxide and aluminum electrodes. Light‐emitting devices fabricated from PMA/PPV multilayers were found to exhibit luminance levels in the range of 20–60 cd/m2, a thickness dependent turn‐on voltage and classical rectifying behavior with rectification ratios greater than 105. In sharp contrast, the devices based on SPS/PPV exhibited near symmetric current–voltage curves, thickness independent turn‐on voltages and much lower luminance levels. The significant difference in device behavior observed between these two systems is primarily due to a doping effect induced either chemically or electrochemically by the sulfonic acid groups of SPS. It w...

Indium contamination from the indium–tin–oxide electrode in polymer light‐emitting diodes

Abstract: We have found that polymer light‐emitting diodes (LEDs) contain high concentrations of metal impurities prior to operation. Narrow peaks in the electroluminescence spectrum unambiguously demonstrate the presence of atomic indium and aluminum. Rutherford backscattering spectroscopy (RBS) and x‐ray photoelectron spectroscopy (XPS) depth profiling data corroborate this result. An average indium concentration of 5×1019atoms/cm3 originating from the indium–tin–oxide (ITO) electrode has been found in the polymer layer.

Adsorption of monolayers of P2Mo18O626- and deposition of multiple layers of Os(bpy)32+-P2Mo18O626- on electrode surfaces

Abstract: The unusually strong, irreversible adsorption of monolayer quantities of the P2Mo18O626- anion on glassy carbon, highly ordered pyrolytic graphite, indium tin oxide, and gold-coated quartz electrodes was examined by electrochemical, spectroelectrochemical, and quartz crystal microgravimetric techniques. A very simple method was developed to deposit multiple layers of composites consisting of alternating layers of the P2Mo18O626- anion and large, multiply-charged cations such as Os(bpy)32+. The resulting deposit is stable and exhibits electroactivity from both of the components that reflects the structure and ionic conductivity of the solid multilayer.

In Situ Observation of 2-Dimensional Clustering during Electrophoretic Deposition

Abstract: Electrophoretic deposition of micron-sized polystyrene latex particles on an indium tin oxide (ITO) electrode was studied in situ using optical microscopy. Strong 2-dimensional clustering of the particles on the electrode surface was observed upon application of a potential. The clustering decreases somewhat with increasing salt concentration. Upon reversal of the direction of the field, the clusters broke up. The aggregation on the electrode cannot be explained by DLVO or dipole interactions. A possible interpretation may be formulated in terms of electro-osmotic flow.

Transparent multilayer device

Abstract: A transparent multilayer device which reflects light in the infrared region of the spectrum while transmitting light in the visible region of the spectrum. The device comprises a multilayered polymer film and a transparent conductor. The multilayered polymer film preferably comprises layers of a semi-crystalline naphthalene dicarboxylic acid polyester having an average thickness of not more than 0.5 microns and layers of a second polymer having an average thickness of not more than 0.5 microns. The layers of semi-crystalline naphthalene dicarboxylic acid polyester preferably have a positive stress optical coefficient. The transparent conductor comprises at least one layer containing a metal or a metal compound in which the metal compound is preferably selected from the group consisting of metal oxides, metal alloys, and combinations thereof. Silver and indium tin oxide are particularly preferred transparent conductors. The transparent multilayer devices may be applied to the surface of a glass or plastic substrate, such as an exterior window in a building, or to a windshield or window in an automobile, truck, or aircraft.

Effects of doping dyes on the electroluminescent characteristics of multilayer organic light‐emitting diodes

Abstract: We report the effects of dyes doped in the emitting layer on the electroluminescent characteristics of multilayer organic light‐emitting diodes (LEDs) using a polysilane polymer, poly(methylphenylsilane) (PMPS), as the hole transporting material. We formed the emitting layer by dispersing in poly(styrene) (PS), one of four dyes whose fluorescence ranged from blue to orange. Two‐ or three‐layer LEDs were prepared by combining PMPS and dye doped PS layers with the indium tin oxide and aluminum used for the hole and electron injecting electrodes, respectively. The three‐layer LEDs had an additional vacuum‐deposited tris‐(8‐hydroxyquinoline) aluminum layer. The electroluminescent (EL) characteristics of these multilayer organic LEDs, such as the current‐voltage–EL intensity curve, the relative EL efficiency, and the EL emitting species, exhibit a marked dependence on the emitting dye. The observed dependence can be described consistently in terms of the dependence of the charge carrier trapping efficiency on ...

On the initial growth of indium tin oxide on glass

Abstract: The initial growth mode of indium tin oxide on glass was studied. An interesting transition from a 3D island growth mode at low temperatures to 2D growth at higher temperature was observed. This transition from the Volmer‐Weber mechanism to the Frank–van der Merwe mechanism occurs at about 150°C. It coincides with the transition from amorphous to polycrystalline growth of the thin films.

Electroluminescent device based on silicon nanopillars

Abstract: Silicon nanopillars were fabricated by using deep UV lithography, highly anisotropic silicon reactive ion etching based on fluorine chemistry, and high‐temperature thermal oxidation for further thinning. Pillars with a diameter below 10 nm and a height in the 0.4–0.6 μm range were obtained while lying on a very smooth bottom silicon surface. An isolating transparent polymer was then used to fill in the etched area containing the pillars and, therefore, planarize and isolate the pillars. Oxygen plasma was used in order to remove the resistance from the top of the pillars. They were then contacted by a thin contact layer (gold or indium tin oxide), evaporated on the top of them. An Ohmic contact was also formed on the back side of the wafer. The obtained device showed rectifying behavior and forward voltages exceeding 10–12 V electroluminescence was observed, visible with the naked eye.

Preparation and electrical properties of ITO thin films by dip-coating process

Abstract: Indium tin oxide (ITO) thin films were prepared on quartz glass substrates by a dip-coating process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. The ITO thin films containing 0 ∼ 20 mol% SnO2 were successfully prepared by heat-treatment at above 400 °C. Chemical stability of sol were investigated by using a FTIR spectrometer. The electrical resistivity of the thin films decreased with increasing heat-treatment temperature, that is carrier concentration increased, and mobility decreased with increasing SnO2 content. The ITO thin films containing 12 mol% SnO2 showed the minimum resistivity of ρ=1.2 × 10−3 (Ω cm). It also showed high carrier concentration of N=1.2 × 1020(cm−3) and mobility μH=7.0(cm2 V−1 s−1).

Emission enhancement in single-layer conjugated polymer microcavities

Abstract: We have studied the luminescence properties of microcavities which are formed by a single layer of poly(para‐phenylenevinylene) sandwiched between a dielectric mirror coated with a conducting indium tin oxide layer and a semitransparent metal electrode. Compared with a device without cavity structure, the spectral and spatial emission are significantly narrowed, and the forward emission intensity is enhanced. We measure a spectral linewidth (full width at half maximum) of the cavity modes of about 4 nm in photoluminescence and 20 nm in electroluminescence and an enhancement of luminescence intensity in the forward direction of more than an order of magnitude. The implications of the narrowing of the emission and possible transfer mechanisms for excitation energy are discussed.

Transparent temperature sensor for an active matrix liquid crystal display

Abstract: A temperature sensor for the liquid crystal portion of a liquid crystal display assembly which includes a thin layer of transparent conductive material which is spread across the viewing area of the display. This layer of transparent conductive material can provide heat to warm up the display when a large voltage is put across it, and can also be used to measure liquid crystal temperature. It is known that the resistance of materials such as indium tin oxide (ITO) changes at a known rate with respect to temperature. By using this transparent layer of material in the stacked elements of a liquid crystal display assembly, an accurate reading of the liquid crystal temperature can be made.

Effect of oxygen concentration in the sputtering ambient on the microstructure, electrical and optical properties of radio-frequency magnetron-sputtered indium tin oxide films

Abstract: Indium tin oxide (ITO) films have been prepared by radio-frequency (rf) magnetron sputtering. The effect of oxygen concentration in the sputtering ambient on the structure and properties of ITO films are investigated. The films have a preferred orientation in the (440) plane. The presence of oxygen during sputtering enhances the crystallization of the film. Film grain size increases as more oxygen is added. According to the XPS measurements, the addition of oxygen reduces the oxygen-deficient region of the film. Hence the optical transmittance of the film is improved while film conductivity decreases.

Electrode interface effects on indium-tin-oxide polymer/metal light emitting diodes

Abstract: A spin‐coated doped‐polymer light emitting diode is studied. Blue electroluminescence decays within 1 h. X‐ray reflectivity analysis of the aged diode shows the formation of an interfacial layer made of the ITO semitransparent electrode indiffused into the polymer. X‐ray reflectivity stands as a powerful tool for aging studies of organic semiconducting devices.

Estimation and verification of the electrical properties of indium tin oxide based on the energy band diagram

Abstract: Indium tin oxide (ITO) is a transparent conducting oxide used in a variety of optoelectronic applications. In order to optimize the electrical conductivity of ITO thin films it is necessary to determine this property as a function of optimum electron concentration (e.g., doping of In2O3 with Sn). A new software program called CRYSTAL 92 is used to determine the energy band diagrams of In2O3 and In2O3 doped with Sn. Using the curvature of the conduction bands, the effective mass of the electrons is estimated and an empirical relationship is established between the effective mass and free carrier concentration using experimentally observed optical effective mass values. The importance of the varying electron effective mass in the prediction of the electron mobility, and hence the electrical conductivity, is shown here by comparing the published experimental results with the estimated results. The limiting factor in the electron mobility appears to be either grain boundary scattering or ion impurity scatteri...

Failure phenomena and mechanisms of polymeric light‐emitting diodes: Indium–tin–oxide damage

Abstract: Indium–tin–oxide (ITO) coated on a glass plate as the transparent electrode in polymeric light‐emitting diodes (LEDs) generates some volcano‐like patterns during use especially at a higher applied electric field strength. Such an ITO damage phenomenon is independent of Joule heat, conjugation structure of the polymer, and light‐emission process, but only dependent on the applied electric field strength. The ITO damage, which results from a self‐decomposition reaction, can cause a reduction of lifetime of the device.

Optical and electrical investigations of indium oxide thin films prepared by thermal oxidation of indium thin films

Abstract: Indium oxide thin films have been prepared by thermal oxidation of vacuum‐deposited indium thin films in air in an open furnace at about 600 K. These indium oxide thin films prepared by thermal oxidation have been examined for optical transparency by measuring their optical absorbance as a function of wavelength. From the optical absorption data, optical band gap and the nature of the forbidden energy gap in the indium oxide thin films have been determined. Electrical conductivity measurements have also been carried out on the above oxide films as a function of temperature during heating and cooling cycles in vacuum. It is found that after the first heating, electrical conductivity increases to a significant extent due to removal of point defect clusters due to annealing which contribute to both carrier generation and scattering. From the thermoelectric power measurements carried out, it has been concluded that electrons are the majority carriers in these indium oxide thin films.

Influence of iodine on the electrical and photoelectrical properties of zinc phthalocyanine thin film devices

Abstract: The electrical and photovoltaic properties of the zinc phthalocyanine (ZnPc) and I 2 doped ZnPc thin films, sandwiched between indium tin oxide (ITO) and Al electrodes, were investigated. Doping with iodine brings adequate changes in the characteristics of the device. The devices constitute a metal-insulator-semiconductor (MIS) structure, in which depletion layer is formed in ZnPc, near Al-Al 2 O 3 /ZnPc. The depletion layer width and potential barrier height decrease with I 2 doping. The charge transport phenomenon at higher voltage range appears to be space charge limited conduction (SCLC), in the presence of the discrete trapping level. The position of Fermi level shifts toward the valence band edge, which indicates that I 2 doping increases the P-type conductivity. Various electrical and photovoltaic parameters were determined from the J-V and C-V analysis. The influence of the I 2 doping has been discussed in detail.

Electroluminescence of epitaxial perylene films

Abstract: A multilayered electroluminescent device was constructed with ordered perylene thin films as an emission layer. The epitaxial perylene film was prepared by vapor deposition onto the KCl (001) surface, then removed from the KCl substrate and sandwiched between the hole‐transport layer coated on an indium tin oxide electrode and Al top electrode. In this epitaxial layer, the perylene molecules oriented their molecular planes perpendicular to the electrode surfaces. This epitaxial device emitted an electroluminescence in the longer wavelengths of 560–580 nm due to the ordered dimeric structure. On the other hand, the device with polycrystalline perylene films exhibited an electroluminescence mainly below 500 nm.

Thin film transistor having transparent conductive film

Abstract: According to a transparent conductive film forming method, after an ITO (Indium Tin Oxide) thin film is formed at room temperature by a sputtering method, an annealing treatment is conducted on the film under hydrogen atmosphere at a suitable temperature such as a temperature higher than 200° C.

Long-lived excited state of C60 in C60/phthalocyanine heterojunction solar cell

Abstract: The photovoltaic properties of ITO (indium tin oxide)/C60/H2(pc), (pc=phthalocyanine)/Au sandwich solar cells are investigated. The cell prepared at a higher vacuum (1×10−6 Torr) shows an open‐circuit photovoltage (VOC) of 0.18 V, a short‐circuit photocurrent (JSC) of 89 μA cm−2, a fill factor (ff) of 0.25, and an energy conversion yield (η) of 0.03% when illuminated by white light with 12.5 mW cm−2 intensity. The photocurrent action spectra of the cell reveal that photocurrent is generated at C60/H2(pc) interface with diffusion of C60 excitons because the excited state of C60 has a relatively long lifetime, while the cell prepared at a lower vacuum (3×10−5 Torr) shows a much smaller photocurrent (JSC=1.4 μA cm−2) because oxygen in C60 acts as carrier traps and increases the resistance of C60.

A microfabricated, electrochemiluminescence cell for the detection of amplified DNA

Abstract: An electrochemical cell for the generation and detection of electrochemiluminescence of tris (2,2′-bipyridyl) ruthenium(II) has been microfabricated in silicon. The cell has been designed for use in the detection and quantification of DNA which has been amplified by the polymerase chain reaction. The cell is a vertical assembly of micromachined silicon and glass substrates, containing a gold, thin film cathode and an indium tin oxide, thin film anode. The anode is transparent, enabling the detection of the luminescence by an external photodetector. Preliminary tests have yielded the detection of free TBR concentrations from 10−9 M to 10−3 M with a cell volume of 85 μl.

Patterning of transparent conducting oxide thin films by wet etching for a-Si:H TFT-LCDs

Abstract: The patterning characteristics of the indium tin oxide (ITO) thin films having different microstructures were investigated. Several etching solutions (HC1, HBr, and their mixtures with HNO3) were used in this study. We have found that ITO films containing a larger volume fraction of the amorphous phase show higher etch rates than those containing a larger volume fraction of the crystalline phase. Also, the crystalline ITO films have shown a very good uniformity in patterning, and following the etching no ITO residue (unetched ITO) formation has been observed. In contrast, ITO residues were found after the etching of the films containing both amorphous and crystalline phases. We have also developed a process for the fabrication of the ITO with a tapered edge profile. The taper angle can be controlled by varying the ratio of HNO3 to the HC1 in the etching solutions. Finally, ITO films have been found to be chemically unstable in a hydrogen containing plasma environment. On the contrary, aluminum doped zinc oxide (AZO) films, having an optical transmittance and electrical resistivity comparable to ITO films, are very stable in the same hydrogen containing plasma environment. In addition, a high etch rate, no etching residue formation, and a uniform etching have been found for the AZO films, which make them suitable for a-Si:H TFT-LCD applications.

Microstructure of laser-fired, sol-gel-derived tungsten oxide films

Abstract: Half-micron-thick tungsten oxide films were deposited by the sol−gel method onto indium tin oxide (ITO) coated soda lime silicate substrates. Following a 100 °C prebake, the samples were fired with a carbon dioxide laser at a variety of power densities and translation speeds. The laser-fired tungsten oxide films were characterized by spectrophotometry, electrochemistry, multiangle ellipsometry, and transmission electron microscopy and compared to similar furnace-fired films. The data showed an increase in electrochromic response with increased firing temperature up to the point where crystallization of the tungsten oxide retarded electrochromic response. A window with graded electrochromic properties was made by laser firing.

Influence of surface oxygen on chemoresistance of tin oxide film

Abstract: The oxygen controlled chemoresistance of tin oxide based gas sensors was investigated in the temperature range from 20 to 320 °C. Polycrystalline thin film gas sensors were fabricated by the reactive dc‐magnetron sputtering. The parameters of the sensors were also modified by additional Pt or Sb doping. The effect of surface oxygen species on the chemoresistance was studied by x‐ray photoelectron spectroscopic (XPS) analysis of the surface chemical composition before and after different sample treatments. The oxygen peak at a binding energy 531.8 eV in the XPS core level spectrum was found to be related to the chemisorbed molecular oxygen O−2. The variation of an amount of the O−2 species is found to be the main cause of gas sensitivity of tin oxide films at temperatures from 20 to 230 °C.