Indium Zinc Oxide Thin Films Research Articles

Fabrication of IZO transparent conducting thin films by the use of magnetron sputtering equipped with ion‐beam system

Abstract— Indium zinc oxide (IZO) thin films have been prepared on glass, polycarbonate (PC), and polyethylene terephthalate (PET) substrates by using a radio‐frequency (RF) magnetron sputtering system equipped with an ion gun, and a simple OLED device was made by using IZO film. The influence of the RF power, the Ar gas volume, and the substrate temperature during the deposition process on the roughness and the electrical and optical properties of the films have been investigated. In addition, End‐Hall ion‐beam treatment of the substrates is applied before the sputtering deposition process. The sheet resistance of the IZO films is 25 Ω/□ for the glass, 21 Ω/□ for the PC, and 20 Ω/□ for the PET substrate with a thickness of 150 nm, and the lowest root‐mean‐square (rms) roughness of these IZO films were measured to be 0.58, 0.35, and 0.32 nm for glass, PC, and PET substrate, respectively. The decrease in the sheet resistance of the IZO films becomes evident after the ion‐beam treatment and makes the surface of the thin film more hydrophilic. Relative to non‐treated IZO film, the ion‐beam‐treated IZO anode in the OLED device seems to inject holes into the emitting layer to enhance the current density.

Comparative study of the structural, optical and photocatalytic properties of semiconductor metal oxides toward degradation of methylene blue

Indium oxide (In 2O 3), zinc oxide (ZnO), stannic oxide (SnO 2), and titanium dioxide (TiO 2) thin films were prepared on glass substrates using electron beam evaporation. The samples characterized by UV–vis spectroscopy, diffraction ray-X and scanning electron microscopy techniques. The photocatalytic degradation of methylene blue in an aqueous solution, as a model compound, was investigated using different metal oxides in an attempt to compare the decomposition reaction rate. The progress of degradation was monitored using UV–vis spectrophotometry. The effects of various experimental parameters such as initial concentration of methylene blue (5–10 mg/l), pH of the solution (2–8), annealing temperature (250–550 °C), and catalyst nature and its microstructure were systematically studied in order to achieve maximum degradation efficiency. The results obtained were fitted with the Langmuir–Hinshelwood model to study the degradation kinetics and discussed in detail. Nearly complete degradation was obtained at optimal operational parameters including the higher annealing temperature of thin film and the increase in MB solution pH. The degradation with In 2O 3 was more efficient than with SnO 2, ZnO and TiO 2 films.

Etch characteristics of indium zinc oxide thin films in a C 2F 6/Ar plasma

Dry etching of indium zinc oxide (IZO) thin films was performed using inductively coupled plasma reactive ion etching in a C 2F 6/Ar gas. The etch characteristics of IZO films were investigated as a function of gas concentration, coil rf power, dc-bias voltage to substrate, and gas pressure. As the C 2F 6 concentration was increased, the etch rate of the IZO films decreased and the degree of anisotropy in the etch profile also decreased. The etch profile was improved with increasing coil rf power and dc-bias voltage, and decreasing gas pressure. An X-ray photoelectron spectroscopy analysis confirmed the formation of InF 3 and ZnF 2 compounds on the etched surface due to the chemical reaction of IZO films with fluorine radicals. In addition, the film surfaces etched at different conditions were examined by atomic force microscopy. These results demonstrated that the etch mechanism of IZO thin films followed sputter etching with the assistance of chemical reaction.

High-Bias Stability of Amorphous Gallium Indium Zinc Oxide Thin-Film Transistors Using an O2 Plasma-Treated Insulator

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Stability of thin film transistors incorporating a zinc oxide or indium zinc oxide channel deposited by a high rate sputtering process

A novel rf sputtering technology in which a high density plasma is created in a remote chamber has been used to reactively deposit zinc oxide (ZnO) and indium zinc oxide (IZO) thin films at room temperature from metallic sputtering targets at deposition rates ∼50 nm min−1, which is approximately an order of magnitude greater than that of rf magnetron sputtering. Thin film transistors have been fabricated using IZO with a maximum processing temperature of 120 °C, which is defined by the curing of the photoresist used in patterning. Devices have a saturated field effect mobility of 10 cm2 V−1 s−1 and a switching ratio in excess of 106. Gate bias stress experiments performed at elevated temperatures show a consistent apparent increase in the field effect mobility with time, which is attributed to a charge trapping phenomenon.

Charge pumping method for photosensor application by using amorphous indium-zinc oxide thin film transistors

The study investigated the photoreaction behavior of amorphous indium-zinc oxide thin film transistor (a-IZO TFT), which was thought to be insensitive to visible light. The obvious threshold voltage shift was observed after light illumination, and it exhibited slow recovery while returning to initial status. The photoreaction mechanism is well explained by the dynamic equilibrium of charge exchange reaction between O2(g) and O2− in a-IZO layer. A charge pumping technique is used to confirm the mechanism and accelerate recoverability. Using knowledge of photoreaction behavior, an operation scheme of photosensing elements consist of a-IZO TFT is also demonstrated in this work.

Etch characteristics of indium zinc oxide thin films using inductively coupled plasma of a Cl 2/Ar gas

Inductively coupled plasma reactive ion etching of indium zinc oxide (IZO) thin films masked with a photoresist was performed using a Cl 2/Ar gas. The etch rate of the IZO thin films increased as Cl 2 gas was added to Ar gas, reaching a maximum at 60% Cl 2 and decreasing thereafter. The degree of anisotropy in the etch profile improved with increasing coil rf power and dc-bias voltage. Changes in pressure had little effect on the etch profile. X-ray photoelectron spectroscopy confirmed the formation of InCl 3 and ZnCl 2 on the etched surface. The surface morphology of the films etched at high Cl 2 concentrations was smoother than that of the films etched at low Cl 2 concentrations. These results suggest that the dry etching of IZO thin films in a Cl 2/Ar gas occurs according to a reactive ion etching mechanism involving ion sputtering and a surface reaction.

High Reliable and Manufacturable Gallium Indium Zinc Oxide Thin-Film Transistors Using the Double Layers as an Active Layer

High reliable bottom gate amorphous gallium indium zinc oxide (a-GIZO) thin-film transistors (TFTs) have been fabricated by using the double active layers. Top and bottom layers were CuGaInZnO (CGIZO) and GIZO, respectively. When the plasma-enhanced processes were introduced during fabrication of the TFTs, the TFT with a-GIZO single active layer did not exhibit electrically reliable performance due to forming the conducting surface layer from the plasma damages. The double-active-layer TFT with a CGIZO layer had the reliable performance ( of , of , subthreshold gate swing value of /decade, of ) even under the same processes. This suggested that the Cu atom of CGIZO layer suppressed the carrier concentration during plasma-enhanced processes. The TFTs with double active layer showed excellent stability, which has the threshold voltage shift of at drain current under for .

Stability Improvement of Gallium Indium Zinc Oxide Thin Film Transistors by Post-Thermal Annealing

The effects of post-thermal annealing on the stability of Ga2O3-In2O3-ZnO (GIZO) thin film transistors (TFT) were investigated by comparing the GIZO TFTs annealed for 3 hour and for 65 hours under high-field bias stress, light illumination, and long-term storage in air. We found that the poor stability of the GIZO TFTs under these stresses was remarkably improved after 65 hours' post-thermal annealing at 250 OC. The improvement of the stability is ascribed to the reduction of the trap sites in the GIZO layer and curing of weak atomic bonds otherwise susceptible to breaking during the stress.

Inductively Coupled Plasma Etching of Indium Zinc Oxide Thin Films with HBr ∕ Ar Discharges

High density plasma etching of indium zinc oxide (IZO) thin films was performed in gas mix. As HBr concentration increased, the etch rate was decreased and etch profile was improved. The high degree of etch anisotropy was achieved with decreasing dc-bias voltage and increasing gas pressure. The formation of protective layer, which had a strong effect on the etch profile, was confirmed by surface analyses. The X-ray photoelectron spectroscopy revealed the formation of and compounds. It could be concluded that the etching of IZO films in plasma was governed by ion sputtering along with chemical assistance.

Stability Improvement of Gallium Indium Zinc Oxide Thin Film Transistors by Post-Thermal Annealing

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Self-aligned top-gate amorphous gallium indium zinc oxide thin film transistors

We have demonstrated a self-aligned top-gate amorphous gallium indium zinc oxide thin film transistor (a-GIZO TFT). It had a field effect mobility of 5 cm2/V s, a threshold voltage of 0.2 V, and a subthreshold swing of 0.2 V/decade. Ar plasma was treated on the source/drain region of the a-GIZO active layer to reduce the series resistance. After Ar plasma treatment, the surface of the source/drain region was divided into In-rich and In-deficient regions. The a-GIZO TFT also had a constant sheet resistance of 1 kΩ/◻ for a film thickness of over 40 nm. The interface between the source/drain Mo metal and the Ar plasma-treated a-GIZO indicated a good Ohmic contact and a contact resistivity of 50 μΩ cm2.

Effect of Oxygen Concentration on Properties of Indium Zinc Oxide Thin Films for Flexible Dye-Sensitized Solar Cell

Indium zinc oxide (In2O3–ZnO, IZO) thin films were prepared with variation of oxygen concentration in Ar sputtering gas using rf magnetron sputtering system. Transmittance was greatly improved from 75 to 90% since surface roughness slightly decreased by adding oxygen and low resistivity of 3.28×10-4 Ω cm was achieved at 0.4% oxygen concentration. The performance of dye sensitized solar cell (DSSC) was also studied by fabricating cells with IZO thin films using UV/ozone treatment. According to the results, the efficiency was strongly affected by both transmittance and resistivity of IZO thin films deposited at different oxygen concentrations. Finally, the highest efficiency of 3.11% was achieved from IZO films deposited with 0.4% oxygen concentration, which exhibits a promising application of IZO thin films to flexible DSSC.

Room Temperature Deposited Enhancement Mode and Depletion Mode Indium Zinc Oxide Thin Film Transistors

Enhancement mode and depletion mode indium zinc oxide (IZO) thin film transistors (TFTs) were fabricated on glass substrates using rf magnetron sputtering deposition at room temperature. Plasma enhanced chemical vapor deposited SiO2 or SiNx was used as the gate insulator. The enhancement mode TFTs showed excellent pitch-off and the threshold voltage was 0.75V. The drain current on-to-off ratio was >106. The maximum field effect mobility in the channel was 308 cm2.V-1.s-1. The depletion mode TFTs had a threshold voltage of -2.5V. The drain current on-to-off ratio was >105. The maximum field effect mobility in the channel was 14.5 cm2.V-1.s-1.

Indium Zinc Oxide Thin Films Deposited by Sputtering at Room Temperature

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Carrier concentration dependence of Ti∕Au specific contact resistance on n-type amorphous indium zinc oxide thin films

Ti ( 200 Å ) ∕ Au ( 800 Å ) Ohmic contacts to n-type amorphous indium zinc oxide (IZO) films with carrier concentrations of (1×1015)–(5×1020)cm−3 showed as-deposited specific contact resistances in the range of (3×10−1)–(1×10−4)Ωcm2. Postgrowth annealing from 200to500°C resulted in significant improvement in contact resistances due to increase of the carrier concentration in the near surface region of IZO layer, which can be attributed to the formation of Ti–O alloy phases that induce oxygen vacancies in the IZO. After annealing at 500°C, the lowest contact resistance of 8×10−6Ωcm2 was achieved in the sample with carrier concentration of 5×1020cm−3. Temperature dependent measurement showed that tunneling was dominant transport mechanism in the contacts on the most highly doped films (n∼5×1020cm−3) and thermionic emission on the most lightly doped films (n∼1×1015cm−3).

대면적 상온 Indium Zinc Oxide 투명 도전막의 물성 특성 비교

An Indium Zinc Oxide(IZO) transparent conductive layer was deposited on a large size glass substrate by using magnetron dc sputtering method with varying a deposition temperature. As the deposition temperature decreased to a room temperature, the sheet resistance of IZO film increased. But this deposition temperature range is included in an applicable to a device. From a standpoint of the sheet resistance, the differences of the sheet resistance were not great and the uniformity of the layer was uniformed around 10%. Crystallization particles were shown on the surface of the layer as deposition temperature increased, but these particles were not shown on the surface of the layer as deposition temperature decreased to the room temperature. It didn't make a scrap of difference in a transmittance of varying deposition temperature. Therefore, it is concluded that IZO thin film manufactured by the room temperature deposition condition can be used as a large size transparent conductive layer of a liquid crystal display device.

Solution-Processed Indium-Zinc Oxide Transparent Thin-Film Transistors

Transparent thin-film transistors (TTFTs) with an indium-zinc oxide (IZO) active layer by the solution-processed deposition method were fabricated and their TFT characterization was examined. Solution-processed IZO thin films were amorphous and highly transparent with >90% transmittance in the visible region with an optical bandgap of 3.1 eV. Spin-coated IZO TTFTs were operated in depletion mode and showed a field-effect mobility as high as 7.3 cm 2 /V s, a threshold voltage of 2.5 V, an on/off current ratio greater than 10 7 , and a subthreshold slope of 1.47 V/decade.

Indium zinc oxide thin films deposited by sputtering at room temperature

The deposition of amorphous indium zinc oxide (IZO) thin films on glass substrates with n-type carrier concentrations between 10 14 and 3 × 10 20 cm −3 by sputtering from single targets near room temperature was investigated as a function of power and process pressure. The resistivity of the films with In/Zn of ∼0.7 could be controlled between 5 × 10 −3 and 10 4 Ω cm by varying the power during deposition. The corresponding electron mobilities were 4–18 cm 2 V −1 s −1.The surface root-mean-square roughness was <1 nm under all conditions for film thicknesses of 200 nm. Thin film transistors with 1 μm gate length were fabricated on these IZO layers, showing enhancement mode operation with good pitch-off characteristics, threshold voltage 2.5 V and a maximum transconductance of 6 mS/mm. These films look promising for transparent thin film transistor applications.

Influence of ZnO buffer layer thickness on the electrical and optical properties of indium zinc oxide thin films deposited on PET substrates

The influence of the ZnO buffer layer thickness on the electrical and optical properties of In 2O 3–10 wt.% ZnO and ZnO bilayers deposited on polyethylene terephthalate (PET) substrates by RF magnetron sputtering were investigated. The optimum ZnO buffer layer thickness was found to be 90 nm which gives the lowest electrical resistivity of the bilayer of IZO and ZnO deposited on the PET substrate. The surface roughness decreases and diffusion of moisture and gas is more efficiently restrained, which contributes to lower the resistivity of the bilayer as the ZnO buffer layer thickness is increased. On the other hand, the total resistivity of the bilayer increases as the ZnO buffer layer thickness is increased because the resistivity of ZnO is higher than that of IZO. Introduction of a ZnO buffer layer does not nearly affect the IZO/ZnO/PET sample.