Shigeyuki Seki

Highly-conducting indiumtin-oxide transparent films fabricated by spray CVD using ethanol solution of indium (III) chloride and tin (II) chloride

Abstract Tin-doped In2O3 (indiumtin-oxide) films were deposited by a simple and inexpensive spray CVD system. An ethanol solution of indium (III) chloride and tin (II) chloride was sprayed onto a glass substrate heated at 300–350 °C in air using a perfume atomizer. The average optical transmission in the visible range was higher than 83% for the films as-deposited and the films annealed at 600 °C in N2–0.1% H2. The resistivities of the as-deposited ITO films were on the order of 10−4 ohm/cm; the minimum resistivity was 1.9×10−4 ohm/cm. Annealing at 600 °C in a N2–0.1% H2 atmosphere reduced the minimum resistivity to 9.5×10−5 ohm/cm (thickness, 190 nm; composition, approximately 4.4 at.% Sn; carrier concentration, 1.8×1021 cm−3; mobility, 40 cm2/V s); this resistivity is probably the lowest among films prepared by chemical processes, and approximately compatible with the reported minimum, 7.7×10−5 ohm/cm deposited by a PVD process (pulsed laser deposition) by Ohta et al. [Appl. Phys. Lett., 76 (19) (2000) 2740].

Indium–tin-oxide thin films prepared by dip-coating of indium diacetate monohydroxide and tin dichloride

Abstract Tin-doped In 2 O 3 (ITO) films were prepared by the dip-coating method using an ethanol solution of indium diacetate monohydroxide, In(OH)(CH 3 COO) 2 , and tin dichloride, SnCl 2 ·2H 2 O, with 2-aminoethanol (monoethanolamine), H 2 NC 2 H 4 OH. The influence of the tin concentration was investigated between 0 and 20 at.% Sn. The composition of the films (thickness ∼90 nm) approximately agreed with that of the solution when the dipping and the heating at 600°C in air for 30 min were repeated three times. The lattice constant of the ITO films increased by the tin addition and annealing at 600°C for 1 h in a nitrogen flow. The films were highly transparent in the visible range. At 6.4 at.% Sn, the maximum carrier concentration (6.2×10 20 cm −3 ) and minimum resistivity (5.8×10 −4 Ω cm) were obtained after annealing in nitrogen (oxygen partial pressure ∼2.0 Pa). The mobilities of the ITO films (∼10 cm 2 V −1 s −1 ) were almost independent of the film composition and the annealing. The mobilities of the undoped In 2 O 3 films were ∼40 cm 2 V −1 s −1 .

Fabrication of indium–tin-oxide films by dip coating process using ethanol solution of chlorides and surfactants

Highly-conductive ITO transparent films were deposited by the dip coating process. An ethanol solution of indium (III) chloride, InCl3·3.5H2O, and tin (II) chloride, SnCl2·2H2O [Sn/(In+Sn), 5 at.%] was successfully dip coated on a Corning #7059 glass substrate by the addition of a surfactant [Sorbon T-80 (non-ionic type); polyoxyethylene sorbitan fatty acids esters]. The dip coating (withdrawal rate, 10 or 28 cm/min) and the heating in air at 600 °C for 1 h were repeated 10 times to fabricate the ITO film with a resistivity of approximately 2×10−3 Ω·cm. Post-deposition annealing in a N2–0.1% H2 atmosphere drastically lowered the resistivity to approximately 2.5×10−4 Ω·cm. This value is lower than most of the reported minimums (4×10−4 Ω·cm) for the thicker ITO films fabricated by the dip coating process.

Formation of indium-tin-oxide films by dip coating process using indium dipropionate monohydroxide

Indium-tin-oxide (ITO) transparent conducting films were successfully prepared by dip coating using a novel precursory material, indium dipropionate monohydroxide, In(OH)(C 2 H 5 COO) 2 , which was synthesized by refluxing propionic acid (C 2 H 5 COOH) with indium oxide (In 2 O 3 ) powders for 12 h. The coating solution consisted of indium dipropionate monohydroxide and tin tetrachloride, SnCl 4 .SH 2 O, dissolved in propionic acid (concentration of total metal ions, 0.1 mol/l; Sn/(In+Sn), 0.1, 3, 5, 10 and 15 at.%). The dip coating (withdrawal rate: 10 cm/min) and the heating on a hot plate (∼400°C, 5 min) were repeated 40 times to fabricate ∼ 200-nm-thick ITO films. The resistivity of the as-deposited films remarkably decreased by increasing the film thickness to ∼200 nm; ∼1.9×10 3 ohm cm was achieved for the ITO films with 5 at.% Sn. Annealing at 600 °C for 1 h in a N 2 -0.1% H 2 atmosphere further lowered the resistivity. The minimum value at the present (3.1 × 10 -4 ohm cm) was compatible with the reported minimums for the previous dip-coated films. The influence of the tin concentration and film thickness on the carrier electron concentration and the mobility was discussed and compared with other dip-coated ITO films.

Indium-tin-oxide films prepared by dip coating using an ethanol solution of indium chloride and tin chloride

Abstract Tin-doped indium oxide (ITO) films were deposited successfully by the dip coating process onto Corning 7059 glass substrates using an ethanol solution of indium (III) chloride, InCl 3 ·3.5H 2 O and tin (II) chloride, SnCl 2 ·2H 2 O [Sn/(In+Sn), 5 atm.%] with a surfactant, which improved the contact between the glass substrate and the coating solution. Film thickness and the resistivity were investigated as a function of the withdrawal rate and the number of repeated dip coatings. The 10-layer films were annealed in a N 2 –0.1%H 2 atmosphere by which the carrier concentration and the mobility increased; the lowest resistivity obtained was 5.7×10 −4 Ω cm (film thickness: 57 nm; carrier concentration: 4.8×10 20 cm −3 , mobility: 20 cm 2 V −1 s −1 ).

EVOLUTION OF WATER VAPOR FROM INDIUM-TIN-OXIDE THIN FILMS FABRICATED BY VARIOUS DEPOSITION PROCESSES

Tin-doped In2O3 (indium-tin-oxide) transparent conducting films are widely used as electrodes of liquid crystal displays and low-E windows. In the present study, a systematic TDS study was undertaken for ITO films fabricated by various deposition processes; such as PVD, dip coating and spray deposition. Water vapor was the main gas evolved from the films; gas evolution from the silicon substrate was negligible. The evolution proceeded via two steps at approximately 373 and 473-623 K. The amount of the evolved water was in the order: (dip-coated film)>(PVD films)> (spray-deposited film). This order was identical to that of the films resistivities.

TG-DTA-MS of chromium(III) formate

Abstract The thermal decomposition of chromium(III) formate pentahydrate, Cr3(OH)2(HCO2)7·5H2O, in helium atmosphere and 20% O2 in helium atmosphere has been successfully studied by means of TG-DTA-MS, i.e., thermogravimetry-differential thermal analysis (TG-DTA) coupled with evolved gas analysis (EGA) using mass spectrometry (MS). The TG-DTA-MS is useful to interpret the complicated successive reactions and to determine the mechanism of the thermal decomposition. The thermal process in He atmosphere proceeded by four steps, while in 20% O2–He atmosphere it proceeded by three steps. The decomposition scheme of Cr3(OH)2(HCO2)7·5H2O in He atmosphere was proposed by the following decomposition mechanism via formation of three intermediates: Cr 3 ( OH ) 2 ( HCO 2 ) 7 ·5 H 3 O → Cr 3 ( OH ) 2 ( HCO 2 ) 7 ·2 H 2 O +3 H 2 O Cr 3 ( OH ) 2 ( HCO 2 ) 7 ·2 H 2 O → Cr 3 ( OH ) 2 ( HCO 2 ) 7 +2 H 2 O Cr 3 ( OH ) 2 ( HCO 2 ) 7 → Cr 2 O 3 + Cr ( HCO 2 ) 3 + CO +3 CO 2 +3 H 2 2 Cr ( HCO 2 ) 3 → Cr 2 O 3 +3 CO +3 CO 2 +3 H 2 . After the decomposition, a slight mass loss was observed with a sharp exothermic crystallization of Cr2O3 due to evolution of H2. In 20% O2–He atmosphere, a drastic exothermic mass loss accompanying evolution of CO2, H2O and H2 was explicable by one step combustion of the dehydrated formate, and a small amount of mass loss observed with a crystallization of Cr2O3 was attributed to evolution of O2. The decomposition process without an intermediate was indicated by the temperature increase of the specimen produced by combustion heat.

Effects of silver deposition on 405nm light-driven zinc oxide photocatalysta)

A silver-loaded zinc oxide (Ag∕ZnO) photocatalyst was fabricated by chemical deposition, followed by an annealing process using a 405-nm-light-driven ZnO fiber. Silver oxide (Ag2O) was deposited on the ZnO fiber with the same method of chemical deposition using a silver-nitrate solution. Ag2O was also decomposed to Ag by annealing at 600°C in a N2 flow. The authors found that the Ag∕ZnO photocatalyst had a fiber structure and that there was 405-nm-light activity. The Ag∕ZnO photocatalyst containing 0.02at.% Ag obtained via a 3.7×10−3mol∕l AgNO3 solution had the highest photocatalytic activity of all the samples.

Formation of indium oxide thin films fabricated by a dip-coating process using indium 2-ethylhexanoate monohydroxide

Abstract The thermal change of indium 2-ethylhexanoate monohydroxide, In(OH)(O2CCH(CH2CH3)(CH2)3CH3)2, to form indium oxide, In2O3, thin film was investigated by TG–DTA–MS in a He–20%O2 atmosphere with a minute amount of specimen (∼0.1 mg) in order to clarify the formation process of the indium-tin-oxide transparent conducting films (thickness, ∼240 nm). The total mass loss at 500 °C (67.9%) agreed approximately with the value (66.8%) corresponding to the formation of In2O3 from In(OH)(O2CCH(CH2CH3)(CH2)3CH3)2. The main mass loss at approximately 250–350 °C can be divided into two steps. In the first step, the evolution of 2-ethylhexanoic acid CH3(CH2)3(CH2CH3)CHCOOH was observed. The evolution of water vapor and carbon dioxide was observed in both steps and significant in the second step. A strong exothermic peak was also observed in the second step. A small amount of water vapor was detected at ∼130–190 °C. A reaction mechanism was proposed.

Characteristics of vanadium-doped indium oxide thin films for organic light-emitting diodes fabricated by spray chemical vapor deposition

An indium oxide transparent electrode for organic light-emitting diodes was fabricated by the inexpensive spray chemical vapor deposition method. The high work function (5.1 eV) necessary for a transparent anode and a hole-injection layer was successfully achieved with a vanadium doping concentration of 1.5 at. % V without any significant increase in resistivity and surface roughness or loss of transparency. The effect of vanadium doping on indium oxide was systematically investigated. The resistivity, average transmittance in the visible range, and surface roughness (Ra) were 1.08 × 10−3 Ωcm, 84%, and 4.0 nm, respectively, for the vanadium-doped indium oxide.