Showing papers on "Indium tin oxide published in 1990"

Low resistivity indium–tin oxide transparent conductive films. II. Effect of sputtering voltage on electrical property of films

Abstract: A low resistivity and high transmittance Sn doped In2O3 (ITO) film was formed on a glass substrate by dc magnetron sputtering and lower sputtering voltage gave a lower resistivity film. At a sputtering voltage of −250 V, the resistivity obtained was 5.0×10−4Ω cm for room temperature substrate, 2.0×10−4Ω cm for 160 °C substrate, 1.9×10−4Ω cm for 200 °C substrate, and 1.2×10−4Ω cm for 460 °C substrate. At a sputtering voltage of −80 V, the resistivity was 1.3×10−4Ω cm for 200 °C substrate. A measurement of Hall effect shows that the decreased resistivity by lower sputtering voltage is not caused by the Hall mobility but by an increased carrier concentration.

Low resistivity indium–tin oxide transparent conductive films. I. Effect of introducing H2O gas or H2 gas during direct current magnetron sputtering

Abstract: When an inline sputtering system is used to make conductive transparent ITO film by the direct current (dc) magnetron sputtering method, it was found that the partial gas pressure of H2O affected the properties of deposited films. When the substrate temperature is at or below 200 °C, the control of H2O partial gas pressure is especially important. Using room temperature substrates, an addition of 2×10−5 Torr of H2O in the sputtering process could form ITO films with good repeatability at a low resistivity of 6.0×10−4 Ω cm. By adding H2O gas, it was possible to solve the issue of increased resistivity in thicker films. The films with added H2O gas have H element immersed into the film and have high carrier concentration. Film transmittance stayed constant with or without H2O gas addition. Similar effect was observed by adding H2 gas instead of H2O gas.

Electrical conductivity of tin oxide films prepared by the sol-gel method

Abstract: A preliminary study concerning the electrical conductivity of tin oxide films obtained by a procedure of dipping sol-gel technique onto glass substrate is reported. The tin oxide-sol solution was prepared starting from stannous chloride. Crystallization of amorphous tin oxide was followed by means of XRD and DTA analyses. The morphology of the coatings was observed by SEM. By this method, it has been verified that tin oxide can be easily doped by means of zirconium and titanium oxides, giving films, in which electrical conductivity is strongly increased.

Plasma Etching of ITO Thin Films Using a CH4/H2 Gas Mixture

Abstract: Plasma etching of ITO (In2O3:Sn indium tin oxide) thin films has been performed using a CH4/H2 plasma. Etching occurs above a substrate temperature (Ts) of 60°C and the etch rate increases with increasing Ts, while amorphous like or polymer-like carbon deposits onto the ITO films below 60°C. The apparent activation energy of the etching is 4.12 kcal/mol (0.18 eV). This small activation energy suggests that the desorption of produced volatiles is the rate-limiting process. Fine ITO patterns (1.5 µmL/S) were obtained using this gas mixture.

Trapping Parameters of Electronic Defectes States in Indium Tin Oxide from AC Conductivity

Abstract: Indium tin oxide films are prepared by in-situ evaporation in a partial vacuum with varying compositions of indium to tin and the ac conductivity of these films is investigated over a frequency range of 1 to 10 kHz. The results show distinct linear regimes in the log–log plots for all compositions, suggesting hopping-like properties. A peak conductivity for 25% Sn composition is observed at all frequencies. Based on the ac hopping theory of Elliot, the binding energy of the defect states is estimated to be between 0.44 to 3.00 eV while the minimum hopping distance varies within the range 1.07 to 7.28 nm. The defect density of states is found to increase with Sn composition from 2 × 1018 eV−1 cm−3 to slightly above 1020 eV−1 cm−3, and deduced to be due to the creation of Sn2+ and Sn4+ defect centres. Indium–Zinn-Oxid-Schichten werden mittels in-situ-Verdampfungstechnik mit variierender Zusammensetzung von Indium zu Zinn hergestellt und die Wechselstromleitfahigkeit dieser Schichten im Frequenzbereich von 1 bis 10 kHz untersucht. Die Ergebnisse zeigen verschiedene lineare Bereiche in der log–log-Darstellung fur alle Zusammensetzungen und weise auf hoppingahnliche Eigenschaften hin. Eine maximale Leitfahigkeit wird fur die 25%-Sn-Zusammensetzung bei allen Frequenzen beobachtet. Auf der Grundlage der Wechselspannungs-Hoppingtheorie von Elliot wird die Bindungsenergie der Defektzustande zu 0,44 bis 3,00 eV berechnet, wahrend der minimale Hoppingabstand innerhalb des Bereichs von 1,07 bis 7,28 nm variiert. Es wird gefunden, das die Defektdichte der Zustande mit der Sn-Konzentration von 2 × 1018 eV−1 cm−3 auf etwas uber 1020 eV−1 cm−3 anwachst, und es wird angenommen, das sie durch die Bildung von Sn2+- und Sn4+-Defektzentren hervorgerufen wird.

Growth of highly oriented tin oxide thin films by laser evaporation deposition

Abstract: Conducting and transparent thin films of tin oxide were prepared by the laser evaporation of an undoped powder‐pressed polycrystalline tin oxide target onto unheated substrates. After characterizing these films, the results reveal that the films are highly oriented and with a grain size ∼0.2 μm. The nearly stoichiometric deposition of tin oxide films with deposition rates exceeding 24 A per pulse was obtained by this method. The lowest resistivity obtained is 3.0×10−3 Ω cm. The visible transmittance (between 4000 and 7000 A) is above 75%.

Electrostatic deposition of LCD color filters

Abstract: Methods for the coating of different closely-spaced areas of an electrode member to produce a color filter matrix thereon. A thin translucent layer of electroconductive composition, such as indium tin oxide (ITO), is applied to isolated areas of the electrode substrate, and selected ones of said areas are charged to one polarity while the other closely-spaced areas are charged to an opposite polarity. Color material is introduced as fine droplets in a volatile vehicle, charged to said opposite polarity, for selective attraction to said selected areas and repulsion from all other areas. The procedure is repeated with different color material droplets for deposition on others of said closely-spaced areas to produce a multi-colored matrix filter, such as on the lower pel electrode or on the upper pixel common electrode of a LCD device. Preferably the ITO layer is coated with a thin polymer layer and the color material is a diffusible dye which is heat-diffused thereinto.

In situ growth of superconducting YBa2Cu3O7−δ thin films on Si with conducting indium‐tin‐oxide buffer layers

Abstract: Superconducting YBa2Cu3O7−δ (YBCO) thin films have been grown in situ on Si with conducting indium‐tin‐oxide (ITO) buffer layers. ITO allows YBCO to be electrically connected to the underlying Si substrate. Both the YBCO film and ITO buffer layer, grown by ion beam sputtering, are textured and polycrystalline with a combined room‐ temperature resistivity of about 2 mΩ cm. Superconducting onsets are 92 K with zero resistance at 68 K.

Indium-Tin Oxide Thin Films Prepared by Chemical Vapor Deposition from Metal Acetates

Abstract: Transparent conductive indium-tin oxide thin films were prepared by a low-temperature atmospheric-pressure chemical vapor deposition method without using an oxygen donor. The raw materials were indium acetate and tin diacetate, which are inexpensive and easy to handle. A 260-nm-thick polycrystalline film was obtained after 1 hour of deposition at a reaction temperature of 300°C. The resistivity was 6.93×1013 Ωcm, and the transmittance was more than 90% in most of the visible range (450–700 nm).

Influence of surface parameters and doping on the sensitivity and on the response times of tin oxide resistive sensors

Abstract: A systematic analysis of the correlations between preparation conditions and physical properties has been carried out on tin oxide films, deposited onto high purity Al2O3 substrates using a variant of the chemical vapour deposition (CVD) technique, with the aim of optimizing the gas-sensing properties of these devices. It has been demonstrated that the nature of the precursor used for tin oxide preparation is of importance for the effective gas performance of the sensor; tin oxide from organometallic precursors is the most suitable active layer for H2 detection and also results in a very fast response time. Sb doping is a very effective way of extending the sensitivity to the largest hydrogen partial pressures. The experimental determination of the surface trap level relative to the chemisorbed oxygen has been performed using a novel fitting procedure of the conductivity transients.

Dependence of the properties of laser deposited tin oxide films on process variables

Abstract: In this paper we report the influence of process variables, viz., substrate temperature, oxygen partial pressure, and external electric field bias, on phase precipitation and microstructure of tin oxide films as revealed by small-angle x-ray diffraction and conversion electron Mossbauer spectroscopy.

Formation of semiconductor circuit

Abstract: PURPOSE: To allow the transfer of circuits without using a costly polishing device by sticking a 1st substrate which is formed of the circuits with a 1st film or the 1st film and at least one layer of a 2nd film to a 2nd substrate on the side where the above-mentioned circuits are formed to each other, then etching away the 1st film and transferring the circuits onto the 2nd substrate. CONSTITUTION: A molybdenum film is first deposited at the 1st film 12 on the 1st substrate 11 consisting of Si. An SiO 2 film is then deposited as the 2nd film 13 thereon and thereafter, TFTs 17 formed by using a-Si as well as picture element electrodes 18 consisting of ITO (indium tin oxide) and wirings consisting of A1 are formed thereon to produce an active matrix 14. An adhesive 15 of, for example, an epoxy system is then applied on the matrix 14 and a PET film is stuck as the 2nd substrate 16 onto the circuits. The assembly is thereafter immersed into hydrogen peroxide and the molybdenum film 12 is completely removed by etching. Finally, the 1st substrate 11 is completely peeled and the above-mentioned circuits are completed. COPYRIGHT: (C)1992,JPO&Japio

Superconducting YBa2Cu3O7-δ thin films on GaAs with conducting indium-tin-oxide buffer layers

Abstract: Superconducting YBa2Cu3O7−δ (YBCO) thin films have been grown in situ on GaAs with conducting indium‐tin‐oxide (ITO) buffer layers. Superconducting onset is about 92 K with zero resistance at 60 K. ITO buffer layers usually form Schottky‐like barriers on GaAs. The YBCO film and ITO buffer layer, grown by ion beam sputter codeposition, are textured and polycrystalline with a combined room‐temperature resistivity of about 1 mΩ cm.

Investigation of buried homojunctions in p‐InP formed during sputter deposition of both indium tin oxide and indium oxide

Abstract: While dc magnetron sputter deposition of indium tin oxide leads to the formation of a buried homojunction in single crystal p-type InP, the mechanism of type conversion of the InP surface is not apparent. In view of the recent achievement of nearly 17-percent global efficiencies for cells fabricated solely by sputter deposition of In2O3, it is presently surmised that tin may not be an essential element in type conversion. A variety of electrical and optical techniques are presently used to evaluate the changes at both indium tin oxide/InP and indium oxide/InP interfaces. Such mechanisms as the passivation of acceptors by hydrogen, and sputter damage, are found to occur simultaneously.

Method for fabricating an indium tin oxide electrode for a thin film transistor

Abstract: A method and resulting structure is described for fabricating a thin film transistor which very effectively uses ITO as its transparent electrode. The method begins by providing a suitable substrate and forming thereover a polysilicon layer. A gate insulator layer is formed upon the polysilicon layer. A gate electrode layer is formed over the gate insulator layer. The gate electrode and gate insulator layers are then patterned to leave the desired gate insulator and gate electrode for the thin film transistor. An insulating layer is formed over the top surface of the structure. The isolating layer is patterned to provide openings to the designated source/drain regions of the thin film transistor. A conductive layer is deposited to make electrical contact to the source/drain regions of the thin film transistor. A silicon nitride passivation layer is formed over the conductive layer. The silicon nitride passivation layer is patterned to leave portions of the conductive layer open. The indium tin oxide (ITO) layer is deposited over the open portions of the conductive layer. The advantages of the process are to avoid the etching of the aluminium layer by the ITO etching process, avoid the ITO damage by the plasma enhanced silicon nitride process, and the solution of the poor adhesion between aluminium to ITO.

Schottky diode properties and the photovoltaic behaviour of indium tin oxide (ITO)/n-GaAs junctions-effect of arsenic deficient GaAs surface

Abstract: Studies on the Schottky barrier properties of ITO/n-GaAs junctions and their photovoltaic behaviour are reported. The junctions were prepared by depositing ITO by reactive thermal evaporation technique on as-cleaned and heat-treated GaAs substrates of (100) orientation. The barrier height of the Schottky diodes prepared on as-cleaned GaAs is 0.83+or-0.02 eV as measured by I-V and C-V methods, and is nearly the same as in the case of many other metal/n-GaAs interfaces. Heat-treated GaAs having arsenic deficient surfaces produced a larger barrier height ( approximately=1.05 eV). As a result of the barrier height enhancement, the ITO/n-GaAs junctions exhibited an increase in the open circuit voltage and photoconversion efficiency from 435 mV and 4.94% to 585 mV and 7.75%, respectively. The efficiency of 7.75% is perhaps the highest for any ITO/GaAs junctions reported so far. The results are discussed on the basis of the defect models for Schottky barrier formation.

Anodic Oxide Film Formation on Tin

Abstract: Thin anodic oxide films have been grown on tin by the galvanostatic technique in buffer solutions (pH 4.20 to 12.06) up to 2 to 2.8 VSCE. The similarity observed between the anodic-charging curves on tin and those on valve metals indicates that an amorphous barrier oxide is first formed on tin, and his oxide undergoes mechanical failures that cause O2 evolution as the thickness increases. The behavior of tin during anodic oxidation resembles in many respects the kinetics of anodization of valve metals. This conclusion has been deduced from the linearity between the logarithm of current density (CD) and (1) the logarithm of the oxide formation rate, (2) the reciprocal capacity, and (3) the potential. Ionic transport under high electric fields according to the Verwey model is responsible for oxide growth on tin. While the efficiency for oxide formation is high for solutions of pH = 10 and below, it decreases appreciably at pH = 12 because of the increase of oxide dissolution.

Fluorine-Doped Indium Oxide Thin Films Prepared by Chemical Vapor Deposition

Abstract: Transparent conductive fluorine-doped indium oxide thin films were prepared by an atmospheric-pressure chemical vapor deposition method without using an oxygen donor. The raw materials were indium 2-ethylhexanoate and indium fluoride. The polycrystalline films were obtained at a reaction temperature in the range of 330–430°C. For the 57.8-nm-thick film deposited at 400°C, the resistivity was 2.89×10-4 Ωcm, and the transmittance was more than 85% in most of the visible range (470–700 nm). The effects of fluorine doping on the deposition rate, structure and characteristics of the film were discussed by comparing the results with the corresponding values for nondoped indium oxide film.

Effects of oxygen partial pressure during deposition on the properties of ion‐beam‐sputtered indium‐tin oxide thin films

Abstract: Ion‐beam‐sputtered indium‐tin oxide (ITO) films were studied as a function of the oxygen pressure PO2, during deposition. Analysis of electrical transport measurements, Auger electron spectroscopy (AES), and x‐ray photoelectron spectroscopy (XPS) show a self‐consistent correlation of all the results. With increasing PO2 a monotonous decrease is observed in the carrier density, which is found to be directly proportional to the oxygen vacancy concentration. This is based on a direct evaluation of the concentration of In unoxidized species in the film using AES and XPS. The moderate decrease of the electron mobility as PO2 is increased is also attributed to the change in the film oxidation state. The systematic relations between all the parameters investigated in this study yield a better understanding of the deposition process and point in the direction of achieving the best ITO films.

Growth of cadmium selenide layers by electrodeposition

Abstract: Cadmium selenide (CdSe) films have been electrodeposited from a bath containing CdSO4 and SeO2. The pH of the bath was around 2. The deposition was done by short circuiting different substrates like Indium Tin Oxide ITO, molybdenum, sodium selenosulphite etc. to an easily oxidizable electrode (such as Al/Cd) in an electrolytic bath. The temperature of the deposition bath was varied in the range 60 to 85 ° C. The as-grown films were characterized by X-ray diffraction and scanning electron microscopy. Electrical characterization of the ITO/ CdSe/In structure was made by studying the current-voltage characteristics. Optical absorption measurements yielded a direct band gap around 1.65eV.

Method of patterning a transparent conductor

Abstract: A method of forming a pattern of a transparent conducting film such as an indium tin oxide film, formed on the surface of a substrate including Si and being heated. A two-step etching method is employed, in which the transparent conducting film is wet-etched by an aqueous solution of a halogenide and thereafter an interfacial reacted layer generated at the interface of the transparent conducting film and substrate including Si is etched by a plasma etching method using a halogen.