In this study, the structural, electrical, and optical properties of AZO films of various thicknesses are compared. The AZO films were deposited on a glass substrate by FTS (Facing-Target-Sputtering) This research was conducted to find the optimal thickness for Transparent Conductive Oxide (TCO). AZO has suitable properties for TCO such as low resistivity, and high transmittance. Thin films of all thicknesses showed a transmittance of over 80% in the visible light region and electrical properties improved as thickness increased. It was confirmed that the film of 300 nm thick had the best performance due to its low resistivity, and uniform surface. This research is expected to help find optimal conditions in various fields where TCO is used, such as solar cells, displays, and sensors in the future.

For decades, sputtering as a physical vapor deposition (PVD) method has been a widely used technique for film coating processes. The sputtering enables oxides, metals, alloys, nitrides, etc to be deposited on a wide variety of substrates from silicon wafers to polymer substrates. Meanwhile, transparent conductive oxides (TCOs) have played important roles as electrodes in electrical applications such as displays, sensors, solar cells, and thin-film transistors. TCO films fabricated through a sputtering process have a higher quality leading to an improved device performance than other films prepared with other methods. In this review, we discuss the mechanism of sputtering deposition and detail the TCO materials. Related technologies (processing conditions, materials, and applications) are introduced for electrical applications.

Oxide (SiO₂)/Metal(Ag)/Oxide(SiO₂, ITO, ZnO) multilayer films were fabricated using a magnetron sputtering technique at room temperature on Si (p-type, 100) and a glass substrate. The electrical and optical properties of the asymmetric multilayer films depended on the thickness of the mid-layer film and the type of oxide in the bottom layer. As the metal layer becomes thicker, the sheet resistance decreases. However, the transmittance decreases when the metal layer exceeds a threshold thickness of approximately 10~12 nm. In addition, the sheet resistance and transmittance change according to the type of oxide in the bottom layer. If the oxide has a large resistivity, the overall sheet resistance increases. In addition, the anti-reflection effect changes according to the refractive index of the oxide material. The optical and electrical properties of multilayer films were investigated using an ultraviolet visible (UV-Vis) spectrophotometer and a 4-point probe, respectively. The optimum structure is SiO₂ (30 nm)/Ag (10 nm)/ZnO (30 nm) multilayer, with the highest FOM value of 7.7×10^-3 Ω^-1.

Oxide (SnO₂)/metal alloy (Cu(Ni))/oxide (SnO₂) multilayer films were fabricated using the magnetron sputtering technique. The oxide and metal alloy were SnO2 and Ni-doped Cu, respectively. The structural, optical, and electrical properties of the multilayer films were investigated using X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectrophotometry, and 4-point probe measurements, respectively. The properties of the SnO₂/Cu(Ni)/SnO₂ multilayer films were dependent on the thickness and Ni doping of the mid-layer film. Since Ni atoms inhibit the diffusion and aggregation of Cu atoms, the grain growth of Cu is delayed upon Ni addition. For 250℃, the Haccke’s figure of merit (FOM) of the SnO₂ (30 nm)/Cu(Ni) (8 nm)/SnO₂ (30 nm) multilayer film was evaluated to be 0.17×10^-3 Ω^-1.

In this study, functional transparent conducting layers were investigated for Si-based photoelectric applications. Double transparent conductive oxide (TCO) films were deposited on a Si substrate in the sequence of indium tin oxide (ITO) followed by aluminum-doped zinc oxide (AZO). First, we observed that the conductivity and transparency of AZO dominate the overall performance of the double TCO layers. Secondly, the double layered TCO film (consisting of AZO/ITO) deposited by sputtering was compared to a AZO-only film in terms of their optical and electrical properties. We prepared three different AZO films: ITO:3min/AZO:10min, ITO:5min/AZO:7min, and ITO:7min/AZO:4min. The results show that the optical properties (transmittance, absorbance, and reflection) can be controlled by the film composition. This may provide a significant pathway for the manipulation of the optical and electrical properties of photoelectric devices.

We have investigated the properties of Al-doped ZnO (AZO) thin films as functions of atomic layer deposition (ALD) oxidants. AZO transparent conducting oxides (TCOs) layer was deposited by ALD with adding trimethylaluminum (TMA) and diethylzinc (DEZn). AZO films were deposited at low temperature with H2O and O3 as oxidants. Electrical, optical and structural properties of AZO thin films were investigated by 4-point probe, Hall effect measurement, UV-VIS, and AFM. Microstructure and atomic bonding states were investigated by HRXRD and XPS. The resistivity of AZO films grown using H2O was lower than the films grown using H2O and O3, by approximately two orders of magnitude. The differences in oxygen vacancy peak intensity of AZO films were correlated to the optical and electrical properties.

In this study, we propose Ti hole pattern structure on the transparent conductive oxide (TCO) lessdye-sensitized solar cells (DSSCs) using the lift-off process to improve the low light transmittance and lowefficiency caused by opaque Ti electrode. The formation of Ti hole patterns make it possible to move the dyeadsorption and electrolyte. The DSSCs with Ti hole patterns showed a higher photoelectric conversion efficiency(PCE) than those with general structure by 11.1%. As a result, The Ti hole pattern structure can be improved toincrease the light absorption of the dyes and PCE of the TCO-less DSSCs is also increased.

Stainless steel (SS) mesh was used to fabricate photo electrode for flexible dye-seisitzed solar cells(DSSCs) in order to evaluate them as replacements for more expensive transparent conductive oxide(TCO). We fabricated the DSSCs with new type of photo electrode, which consisted of flexible SS mesh coated with 100 nm thickness titanium (Ti) protective layer deposited using electron-beam deposition system. SS mesh DSSCs with protective layer showed higher efficiency than those without a protective layer. The best cell property in the present study showed the open circuit voltage (Voc) of 0.608 V, short-circuit current density (Jsc) of 5.73 mA cm-2, fill factor (FF) of 65.13%, and efficiency (η) of 2.44%. Compared with SS mesh based on DSSCs (1.66%), solar conversion of SS mesh based on DSSCs with protective layer improved about 47%.

In this study, a transparent conductive oxide (TCO)-less dye-sensitized solar cells (DSSCs)was fabricated by using titanium (Ti) electrode to replace the Fluorine-doped tin oxide (FTO) for thereduction of manufacturing cost. Ti film was formed by electron beam evaporation method and the resultsshowed the sheet resistance of Ti electrodes with a thikness of 500 nm similar to FTO. In case of powerconversion efficiency (PCE), a DSSC with Ti electrodes showed a lower value than that with FTO by0.38%. For the investigation of the difference, the DSSCs were measured and analyzed by usingelectrochemical impedance analyzer (EIS).

Because of a waveguiding effect and total internal reflection caused by a difference inrefractive indices, only 20% of generated light is emitted to the air and the rest is trapped or absorbed inthe device. An improvement of outcoupled efficiency of organic light-emitting diodes was studied using amicrolens array. Mold of microlens array was fabricated by using photo-lithography with the AZ9260photoresist, and the microlens array was formed onto the glass substrate using the UV curing agentnamed ZPU13-440. Device structure consists of microlens/glass/ITO/TPD/Alq3/LiF/Al. It was found thatthere is an improvement of external quantum efficiency by about 20% at the same current density for thedevice with the microlens array compared to that of the reference one. Simulated outcoupled efficiencyshows the improvement by about 20% for the device with the microlens array compared to that of thereference one. These results are consistent with the experimental ones

As a method of simple patterning of transparent conductive oxide (TCO) films deposited on flexible substrates, laser direct etching was carried out on TCO films sputtered on polycarbonate (PC) substrates. As a result of different binding energies in TCO films, indium tin oxide (ITO) and indium gallium zinc oxide (IGZO) were more easily etched than zinc oxide with different Nd: YVO4 laser beam conditions.

Performance of organic light-emitting diodes incorporating microlens array was simulated using a Light Tools software. Use of microlens array can help the light to escape out of the device. We simulated a reference device that is consisted of reflection layer, emissive layer, and flat transparent substrate. And in this reference device, outcoupled efficiency of 22% was obtained. Several shapes of microlens were applied such as hemisphere, trapezoid, cone, and rectangular parallelepiped. The results showed the improvement of outcoupled efficiency of the device with microlens compared to that of the reference one. And from the analyses of the simulated data, the obtained appropriate shape of microlens is hemisphere, and the improvement of the device with hemispherical lens is 57% higher than that of the reference one.

Indium Zinc Tin Oxide (IZTO) thin films were developed as an alternative to Indium Tin Oxide (ITO) thin films. ITO material which has been acknowledged with its low resistivity and optical transparency of 85-90% has been used as major transparent conducting oxide (TCO) materials. However, due to the limited source, high price, and instability problems at high temperature of indium, many researches has been focused on indium-saving TCO materials. Mason Group of Northwestern University was reported to expand the solubility limit up to 40% by co-doping with 1:1 ratio of Zn+2 and Sn+4 ions. In this study, the properties of IZTO thin films corresponding to Zn/Sn different ratio were investigated. In addition, the effect of substrate temperature variable to the structural, optical and electrical properties of IZTO thin films was investigated.

Off-axis magnetron sputtering was used for the crystallized ITO thin films deposition at various temperatures from 25 to 120t. The ITO thin films were crystallized at 50t for Si (001) substrates and at 75t for PET substrate. The I`J`O thin films grown onto PET substrate at 120t were crystallized with a (222) preferred orientation. The 160-nm thick ITO films showed a resistivity of about 7 x 10 ? cm and a transmittance of about 84% at a wavelength of 550 rim. Off-axis sputtering can be applied for low temperature crystallization of the ITO films.

We have investigated the structural, electrical and optical properties of Ga-doped ZnO (GZO) thin films prepared by RF magnetron sputtering with laboratory-made ZnO targets containing 1, 3, 5, 7 wt% of Ga2O3 powder as a doping source. The GZO thin films show the typical crystallographic orientation with c-axis regardless of Ga2O3 content in the targets. The 3,000 Å thick GZO thin films with the lowest resistivity of 7×10-4 Ω·cm are obtained by using the GZO (Ga2O3= 5 wt%) target. Optical transmittance of all films shows higher than 80% at the visible region. The optical energy band gap for GZO films increases as the carrier concentration (ne) in the film increases.

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. SnO2 is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5eV. It is known as a transparent conducting oxide because of its low resistivity of 10-3Ωcm and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of SnO2 were investigated. The addition of Y in SnO2 was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of SnO2. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of SnO2 single-doped with Al and Y. {(x/2) Al2O3+(x/2) Y2O3}-SnO2 was used for the source of Al and Y to prevent the evaporation of Al2O3 and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of SnO2 co-doped with Al and Y will be discussed.

This article introduces the characterization of spin coated ZnO transparent conducting oxide on the flexible substrates. As a II-IV compound semiconductor, ZnO has a wide band gap of 3.37 eV with transparent properties. Due to this transparent properties, ZnO materials can be also employed as the transparent conducting electrode materials. Therefore, strong demands have been required for the transparent electrodes with low temperature processing and cheap cost. So, We will investigate the electrical property and optical transmittance of ZnO transparent conducting oxide through the 4-point probe resistivity meter, and ultraviolet-vis spectrometer Lamda 35, respectively.

In this research, we prepared Ga doped zinc oxide(ZnO:Ga, GZO) targets each difference sintering temperature 700℃, 800℃, and doping rate 1 wt.%, 2 wt.%, 3 wt.%. The characteristics of thin film on glass substrates which deposited by facing target sputtering in pure Ar atmosphere are reported. Ga doped zinc oxide film is attracted material through low resistivity, high transmittance, etc. When prepared target powder`s structure was investigated by scanning electron microscope, densification and coarsening by driving force was observed. For each ZnO:Ga films with a Ga2O3 content of 3 wt.% at input power of 45 W, the lowest resistivity of 9.967×10(-4) Ω·cm (700℃) and 9.846×10(-4) Ω ·cm (800℃) was obtained. the carrier concentration and mobility were 4.09 × 10(20) cm-3(700℃), 4.12×10(20) cm-3(800℃) and 15.31 cm2/V·s(700℃), 12.51 cm2/V·s(800℃), respectively. And except 1 wt.% Ga doped ZnO thin film, average transmittance of these samples in the range 350-800 nm was over 80%.

The TiO2/Si3N4/Ag/Si3N4/TiO2 multi layered structure was designed for the possible application of transparent electrodes in PDP (Plasma Display Panel). Multi layered film was deposited on a glass substrate at room temperature by DC/RF magnetron sputtering system and EMP (Essential Macleod Program) was adopted to optimize the optical characteristics of film. During the deposition process, the Ag layer in TiO2/Ag/TiO2 became heavily oxidized and the filter characteristic was degraded easily. In thus study, Si3N4 layer was used as a diffusion buffer layer between TiO2 and Ag. in order to prevent the oxidation of Ag layer in TiO2/Si3N4/Ag/Si3N4/TiO2 structure. It was confirmed that Si3N4 layer is one of candidate materials acting as diffusin barrier between TiO2/Ag/TiO2.

Recently, n-InZnO/p-CuO oxide diode has attracted great attention due to possible application for selector device of 3-dimensional cross-point resistive memory structures. To investigate the detailed properties of InZnO (IZO), we have deposited IZO films on the fused quartz substrate using PLD (pulsed laser deposition) method at oxygen pressure of 1∼100 mTorr and substrate temperature of RT∼600℃. The influence of oxygen pressure and substrate temperature on structural, optical and electrical of IZO films is analyzed using XRD (x-ray diffraction), SEM (scanning electron microscopy), UV-Vis spectrophotometry, spectroscopic ellipsometry (SE) and hall measurements. The XRD results shows that the deposited thin films are polycrystalline over 300℃ of substrate temperature independent of oxygen pressure. The resistivity of films was increased as oxygen pressure and substrate temperature decrease. The thickness and optical constants of the deposited films measured with UV-Vis spectrophotometer were also compared with those of broken SEM and SE results.

Al-doped ZnO film on glass substrate is deposited by ALD in low temperature, using 4-step process (DEZ-H2O-TMA-H2O). To find out the optimal film condition for TCO material, we fabricate Al-doped ZnO films by increasing Al doping concentration at 100℃, so that the Al-doped film of 5 at% shows the lowest resistivity (1.057×10(-2) Ω·cm) and the largest grain size (38.047 nm). Afterwards, the electrical and physical characteristics in Al-doped films of 5 at% are also compared in accordance with increasing deposition temperature. All the films show the optical transmittance over 80% and the film deposited at 250℃ demonstrates the superior resistivity (1.237×10(-4) Ω·cm).

In this study, off-axis magnetron sputtering was used for the crystallized ITO thin films at a low temperature of about 120℃ instead of the conventional RF sputtering because the off-axis sputtering can avoid the damage for the plasma as well as fabrication of thin films with a high quality. The ITO thin films grown on PET substrate at 120℃ were crystallized with a (222) preferred orientation. 58-nm thick ITO films showed a resistivity of about 2 x 10-4 n·cm and a transmittance of about 75% at a wavelength of 550 nm. The transmittance of the ITO thin films by an insertion of SiO2 thin films on ITO films was improved.

In this study, we investigated the optical, electrical, and structural properties of the IGZO(In2O3:Ga2O3:ZnO=1:9:90 wt.%) thin films prepared by RF-magnetron sputtering system under various substrate temperatures. All of the IGZO thin films shows an average transmittance of over the 80% in visible range. Most of all, deposited IGZO thin film at 100 ˚C substrate temperature have ZnO (002) of main growth peak and 17.02 nm of increased grains. And also IGZO thin film have low resistivity(1.35×10(-3) Ω·cm), high carrier concentration(6.62X10(20) cm-3) and mobility(80.1 cm2/Vsec). IGZO thin film have 2.08 mV at surface potential of electric force microscopy(EFM). We suggest that pre-annealing at 100 ˚C can be applied for improving optical, electrical and structural properties.