Transparent Conductive Oxide Films Research Articles

Effects of Ag-doping on the characteristics of AgxNi1-xO transparent conducting oxide film and their applications in heterojunction diodes

AgxNi1-xO transparent conducting oxide film with various Ag mole ratios were prepared via a low-cost sol-gel method, and p-AgxNi1-xO/n-Si heterojunction diodes (HJDs) were fabricated. The effects of various Ag mole ratios on the structure, optical, and electrical properties of AgxNi1-xO films were systematically investigated, and their device applications in p-AgxNi1-xO/n-Si HJDs were examined. The Ag atoms accumulate at grain boundaries and inhibit the grain growth of AgxNi1-xO films. The pristine NiO film exhibits a transmittance exceeding 90% for the visible wavelengths. However, transmittance decreases with the Ag mole ratio. A transmittance hollow occurs at approximately 410 nm in Ag-doped AgxNi1-xO film, attributing to the absorption of surface-plasma-resonance of Ag nanoparticles. The energy gap increases from 3.58 to 3.75 eV for the AgxNi1-xO films with the Ag mole ratio of 0 and 1.8, respectively. Hall measurement indicated that the AgxNi1-xO film is p-type. The pristine NiO film exhibits a very high resistivity (≧106 ohm-cm). The resistivity significantly decreases from 14.8 to 1.88 × 10−4 ohm-cm for the AgxNi1-xO film with the Ag mole ratio of 0.3 and 1.8, respectively. Simultaneously, the hole concentration significantly increases from 1.46 × 1016 to 8.03 × 1022 cm−3. X-ray photoelectron spectroscopy revealed the Ni+3/Ni+2 ratio increases from 0.73 to 1.73 for the AgxNi1-xO films with the Ag mole ratio of 0 and 1.8, respectively. The increased Ni+3/Ni+2 ratio is responsible for increase in the hole concentration. The fabricated p-AgxNi1-xO/n-Si HJDs with Ag mole ratio of 0.5 exhibits a clear rectifying behavior with series resistance and ideality factor of 0.88 kΩ and 2.8, respectively.

Structural optical and electrical properties of a transparent conductive ITO/Al-Ag/ITO multilayer contact.

Indium tin oxide (ITO) is a widely used material for transparent conductive oxide (TCO) films due to its good optical and electrical properties. Improving the optoelectronic properties of ITO films with reduced thickness is crucial and quite challenging. ITO-based multilayer films with an aluminium–silver (Al–Ag) interlayer (ITO/Al–Ag/ITO) and a pure ITO layer (as reference) were prepared by RF and DC sputtering. The microstructural, optical and electrical properties of the ITO/Al–Ag/ITO (IAAI) films were investigated before and after annealing at 400 °C. X-ray diffraction measurements show that the insertion of the Al–Ag intermediate bilayer led to the crystallization of an Ag interlayer even at the as-deposited stage. Peaks attributed to ITO(222), Ag(111) and Al(200) were observed after annealing, indicating an enhancement in crystallinity of the multilayer films. The annealed IAAI film exhibited a remarkable improvement in optical transmittance (86.1%) with a very low sheet resistance of 2.93 Ω/sq. The carrier concentration increased more than twice when the Al–Ag layer was inserted between the ITO layers. The figure of merit of the IAAI multilayer contact has been found to be high at 76.4 × 10−3 Ω−1 compared to a pure ITO contact (69.4 × 10−3 Ω−1). These highly conductive and transparent ITO films with Al–Ag interlayer can be a promising contact for low-resistance optoelectronics devices.

Tuning the Morphology and Properties of Nanostructured Cu-ZnO Thin Films Using a Two-Step Sputtering Technique

Zinc oxide (ZnO) is a wide-band-gap semiconductor that is promising for use as a transparent conductive oxide film. To date, to improve their optoelectrical properties, pristine ZnO films have been doped with metals using various techniques. In this study, nanostructured Cu-ZnO thin films were synthesized using a modified two-step radio frequency magnetron sputtering technique with separate ZnO and metallic Cu targets. Controlling the timing of the Cu/ZnO co-sputtering and ZnO-only sputtering steps afforded a significant change in the resulting nanostructures, such as uniform Cu-ZnO and broccoli-structured Cu-ZnO thin films. Using various measurement techniques, the influence of Cu doping was analyzed in detail. Furthermore, a crystal growth model for the formation of the broccoli-like clusters was suggested. The Cu-ZnO thin films synthesized using this technique demonstrate a highly improved conductivity with some loss in optical transmittance.

Transparent Photonic Crystal Heat Mirrors for Solar Thermal Applications

Numerical calculations are performed to determine the potential of using one-dimensional transparent photonic crystal heat mirrors (TPCHMs) as transparent coatings for solar receivers. At relatively low operating temperatures of 500 K, the TPCHMs investigated herein do not provide a significant advantage over conventional transparent heat mirrors that are made using transparent conducting oxide films. However, the results show that TPCHMs can enhance the performance of transparent solar receiver covers at higher operating temperatures. At 1000 K, the amount of radiation reflected by a transparent cover back to the receiver can be increased from 40.4% to 60.0%, without compromising the transmittance of solar radiation through the cover, by using a TPCHM in the place of a conventional transparent mirror with a In2O3:Sn film. For a receiver operating temperature of 1500 K, the amount of radiation reflected back to the receiver can be increased from 25.7% for a cover that is coated with a In2O3:Sn film to 57.6% for a cover with a TPCHM. The TPCHM that is presented in this work might be useful for high-temperature applications where high-performance is required over a relatively small area, such as the cover for evacuated receivers or volumetric receivers in Sterling engines.

Perovskite Transparent Conducting Oxide for the Design of a Transparent, Flexible, and Self-Powered Perovskite Photodetector.

Transparent and flexible electronic devices are highly desired to meet the great demand for next-generation devices that are lightweight, flexible, and portable. Transparent conducting oxides (TCOs), such as indium-tin oxide, serve as fundamental components for the design of transparent and flexible electronic devices. However, indium is rare and expensive. Herein, we report the fabrication of low-cost perovskite SrVO3 TCO films on transparent and flexible mica substrates and further demonstrate their utilization as a TCO electrode for building a transparent, flexible, and self-powered perovskite photodetector. Superior stable optical transparency and electrical conductivity are retained in SrVO3 after bending up to 105 cycles. Without an external power source, the constructed all-perovskite photodetector exhibits a high responsivity (42.5 mA W-1), fast response time (3.09/1.23 ms), and an excellent flexibility and bending stability after dozens of cycles of bending at an extreme 90° bending angle. Our results demonstrate that low-cost and structure-compatible transition metal-based perovskite oxides, such as SrVO3, as TCO electrodes have huge potential for building high-performance transparent, flexible, and portable smart electronics.

A Combined Experimental and Theoretical Study of Screen-printing High Transparent\xa0Conductive Mesoscopic ITO Films

We have successfully fabricated transparent conductive mesoporous indium tin oxide (TCM-ITO) films by a screen-printing method. The TCM-ITO films possess approximately 22 nm mesopores and obtain electrical conductivity up to 14.96 S/cm by adjusting the mass ratio of cubic-shaped ITO nanoparticles to ethyl cellulose (EC) and precisely controlling the annealing process. The regulation mechanism of EC and the heat-induced recrystallization process of ITO nanoparticles are elaborated. The internal kinetic processes of the films based on different surface states are analysed, and an extensible impedance model is established.

Antireflective Transparent Conductive Oxide Film Based on a Tapered Porous Nanostructure.

A new architecture for antireflection (AR) has been developed to break the trade-off between the optical transmittance and the electrical conduction impeding the performance of transparent conductive oxide (TCO) films. The tapered porous nanostructure with a complex continuous refractive index effectively eliminates reflections from the interfaces between air and the TCO and TCO and the substrate. Compared to the conventional TCO film, the AR TCO film exhibited the same electrical conduction, with an average transmittance of 88.7% in the 400–800 nm range, a 10.3% increase. The new AR TCO film is expected to improve the performance of various optoelectronic devices.

Improvement of characteristics of flexible Al-doped ZnO/Ag/Al-doped ZnO transparent conductive film using silver

In recent years, transparent conductive oxide (TCO) films that can be applied to flexible devices have attracted considerable attention. Among TCOs, indium tin oxide (ITO) is frequently used, but ITO contains the rare metal In and is inflexible. Therefore, the authors focused on an Al-doped ZnO (AZO) transparent conductive film as an alternative material for ITO. The authors prepared films on polyethylene naphthalate (PEN) substrates to prepare flexible electrodes. PEN substrates are sensitive to heat and must be deposited at low temperatures. However, there is a limit to improving the conductivity of AZO film formation at low temperatures. Therefore, the authors focused on the AZO/Ag/AZO multilayer transparent conductive films. The AZO layer was deposited by RF magnetron sputtering, and the Ag layer was deposited by electron beam evaporation. The electrical and optical characteristics were evaluated by changing the deposition conditions during the AZO and Ag deposition. Thus, when the thickness of the Ag layer was changed, the maximum transmittance was obtained at a thickness of 10 nm. Next, the upper AZO film was divided into room temperature/50 °C. When the upper AZO is formed at 50 °C, the already deposited Ag is affected by thermal oxidation. Ag was protected from thermal oxidation by first depositing the upper AZO at room temperature and then applying 50 °C, resulting in improved transmittance and resistivity. Furthermore, the resistivity and transmittance were improved by increasing the deposition rate of the Ag layer due to a decrease in the oxygen content in the Ag layer. Among the formed thin films, the best obtained characteristics were the resistivity of 1.24 × 10−4 Ω cm and the transmittance of 84.8%.

High Haze Ratio-Based ITO Films Prepared on Periodic Textured Glass Surfaces for Thin Film Solar Cells

Light-trapping phenomenon is limited due to non-uniform surface structure of transparent conducting oxide (TCO) films. The proper control of surface structure with uniform cauliflower TCO films may be appropriate for efficient light trapping. We report a light-trapping scheme of SF6/Ar plasma-based textured glass surfaces for high root-mean-square (RMS) roughness and haze ratio of ITO films. It was observed that the variation in Ar flow ratio in SF6/Ar plasma during the inductive coupled plasma-reactive ion etching (ICP-RIE) process was an important factor to improve the haze ratio of textured glass. The SF6/Ar plasma textured glass showed low etching rates due to the presence of various metal elements, such as Al, B, F, and Na. The ITO films were deposited on SF6/Ar plasma-textured glass substrates showed the high RMS roughness (433 nm) and haze ratio (67.8%) in the visible wavelength region. The change in surface structure has a negligible influence on the electrical properties of ITO films. The TCO films deposited on periodic textured glass surfaces with high RMS roughness and haze ratio are proposed for high-efficiency amorphous silicon (a-Si) thin-film solar cells.

Fe co-doping effect on fluorine-doped tin oxide transparent conducting films accelerating electrochromic switching performance

In this study, Fe co-doping into fluorine-doped tin oxide (FTO) films using horizontal ultrasonic spray pyrolysis deposition (HUSPD) is reported as a novel approach to improve their transparent conduction for high-performance electrochromic (EC) devices. To optimize their transparent conducting performance, we adjusted the Fe to F ratio to an atomic percentage of 0, 1, 2, and 3 at% during the film deposition. With the optimized Fe co-doping effect induced at Fe 2 at%, the resulting Fe-doped FTO films exhibited simultaneous improvements in the carrier concentration and Hall mobility which are, attributed to Vo induced by a Fe substitution, and the smooth surface morphology interfering with the growth of the FTO crystallites, respectively. As a result, the Fe-doped FTO films prepared at Fe 2 at% achieve a higher transparent conduction (4.4 ± 0.14 Ω/□ sheet resistance and 83.1% optical transmittance) than the other films with a figure of merit of 3.56 × 10−2 Ω−1. Hence, when these unique films are used in EC devices as a transparent conductive oxide, fast switching speeds (6.1 s coloration speed and 5.1 s bleaching speed) and a high coloration efficiency (CE) of 48.2 cm2/C occur as unique effects of the Fe-doped FTO films, accelerating the insertion of Li+ and electrons into the WO3 films, which act as an active EC material and enhancing the electrochemical activity. Therefore, our study provides promising insight into unique transparent conductive oxide films for high-performance EC devices.

Transparent conductive oxide film with antireflective properties for Cu<sub>2</sub>ZnSnS<sub>4</sub> solar cells

At present, there are several kinds of broadband antireflection coatings (ARCs). For the flat multilayer ARC, it usually contains double, triple, or up to 4 layers. It has been demonstrated that the performance of a single layer coating is not good enough across the desired spectral range. Multiple layer ARCs have much better performance for broadband solar cells (SCs). When inspecting the antireflection structure of Cu<sub>2</sub>ZnSnS<sub>4</sub> solar cells (CZTSSCs), it is shown that the transparent conductive oxide (TCO) of traditional CZTSSCs does not have an satisfactory antireflective performance. This paper aims to investigate a way to increase the incident light transmitted into CZTSSCs, and thus improving the efficiency of solar cells by studying the use of the antireflective effect of a TCO film. It introduces a new type of TCO film with better antireflective properties across a wide wavelength range. An SiO<sub>2</sub>/ZnO antireflective TCO (ATCO) is designed under AM1.5 illumination. In order to measure the antireflective effect over the 300–800 nm wavelength range, an effective average reflectance method (EAR) is introduced. Considering the effect of the refractive index dispersion and the coupling of the TCO or ATCO films with the active layer, in this paper we use a multi-dimensional transfer matrix to optimize the thickness of each key layer to accurately confirm the best antireflective effect. In addition, the optimized TCO film and the optimized ATCO film in CZTSSCs are compared and analyzed by means of EAR. The result shows, through the comparison of the antireflection between conventional TCO CZTSSCs and ATCO CZTSSCs, that there are considerable differences in final optimal reflectivity between TCO layer and ATCO film. For the conventional CZTSSC, the optimal effective average reflectance of TCO layer is 5.6%, and the lowest reflectivity in the waveband from 400 nm to 500 nm is 6.9%. In addition, the corresponding values obtained in the new ATCO CZTSSC are 3.8% and 1.6% respectively. These apparent changes in reflectivity are appealing in that the new ATCO films can effectively reduce light loss and improve the efficiency of photovoltaic conversion.

Research progress of tin oxide-based thin films and thin-film transistors prepared by sol-gel method

Transparent conductive oxide (TCO) films and transparent oxide semiconductor (TOS) films have been widely adopted in solar cells, flat panel displays, smart windows, and transparent flexible electronic devices due to their advantages of high transparency and good conductivity and so on. Most of TCO and TOS films are mainly derived from indium oxide, zinc oxide and tin oxide. Among these materials, the In element is toxic, rare and expensive for indium oxide film, which will cause environmental pollution; zinc oxide film is sensitive to acid or alkali etchants, resulting in a poor formation of film patterning; tin oxide film is not only non-toxic, eco-friendly, and cheap but also has good electrical properties and strong chemical stability. Thus, tin oxide has a great potential for developing the TCO and TOS films. At present, the film is prepared mainly by the vacuum deposition technique. The drawbacks of this technique are complex and expensive equipment system, high energy consumption, complicated process and high-cost production. However, compared with the vacuum deposition technique, the sol-gel method has attracted extensive attention because of its virtues such as simple process and low cost. In this paper, we review the development status and trend of TCO and TOS films. First, the structural characteristics, conductive mechanism, element doping theory and carrier scattering mechanism of tin oxide thin films are introduced. Then the principle of sol-gel method and correlative film fabrication techniques are illustrated. Subsequently, the application and development of tin oxide-based thin films prepared by sol-gel method in n-type transparent conductive films, thin-film transistors and p-type semiconductor films in recent years are described. Finally, current problems and future research directions are also pointed out.

Insight of the doping mechanism of F and Al co-doped ZnO transparent conductive films

Transparent conductive oxide (TCO) films, as transparent electrodes, are widely used in thin-film solar cells. The performance of TCO film has a significant influence on the conversion efficiency of the film solar cell fabricated byusing it. Although the conductivity can be improved by increasing the carrier concentration, the transmittance in the long wave will be sacrificed. Therefore, the only feasible method is to increase the carrier mobility within a certain carrier concentration range, rather than increase the mobility by reducing carrier concentration. In this paper, the F and Al co-doped ZnO (FAZO) films are deposited on glass substrates (Corning XG) by an RF magnetron sputtering technique with using a small amount of ZnF<sub>2</sub> (1 wt.%) and Al<sub>2</sub>O<sub>3</sub> (1 wt.%) dopant. The influences of sputtering pressure on the structure, morphology and photoelectric characteristics of the films are respectively investigated by X-ray diffraction analysis, scanning electron microscope, Hall effect measurement, and ultraviolet–visible–near infrared spectrophotometry. All the thin films show typical wurtzite structure with the <i>c</i> axis preferentially oriented perpendicular to the substrate. With the increase of sputtering pressure, the deposition rate of FAZO film decreases, the crystallization quality is deteriorated, surface topography changes gradually from “crater-like” to co-existent “crater-like” and “granular-like”, and the surface roughness increases. The FAZO film deposited at 0.5 Pa presents the optimal performance with a mobility of 40.03 cm<sup>2</sup>/V·s, carrier concentration of 3.92 × 10<sup>20</sup> cm<sup>–3</sup>, resistivity of 3.98 × 10<sup>–4</sup> Ω·cm, and about 90% average transmittance in a range of 380－1200 nm. The theoretical result shows that the co-doping of F and Al takes the advantages of single F and Al doped ZnO films, and overcomes the shortcoming of metal elements doping, which donates the carriers just from doped metal elements. Furthermore, the co-doping of F and Al not only increases the carriers but also reduces the scatterings caused by the inter-orbital interaction of doped atoms. The doped F 2p electron orbitals repel the O 2p and Zn 4s electron orbitals, making them move down and donate electrons. At the same time, the orbitals of Al 3s and Al 3p also make a contribution to the conductivity. After co-doping of F and Al, both the carrier concentration and conductivity increase significantly.

The Polar Solvent Application Method for Organic Transparent Conductive Film Produced by an Inkjet Printing Method

In recent years, flexible electronic devices have attracted much attention. Accordingly, flexible transparent conductive films are being researched actively. The commonly used indium tin oxide (ITO) transparent conductive film has limited flexibility. Therefore, we focused on poly(3,4-ethylenedioxythio- phene)/poly(styrenesulfonate)(PEDOT:PSS) as a substitute material for ITO and are engaged in producing flexible transparent conductive film using inkjet printers. To improve the characteristics of the transparent conductive film produced by inkjet printing, based on prior research, we found that cleaning the film substrate with ultraviolet/ozone (UV/O3) and post-deposition annealing and treatment using polar solvents are effective for thin films. In this study, we examined the method of applying the polar solvent. As a result, we were able to improve the homogeneity of the thin film surface by applying the polar solvent to each thin film lamination layer. The resulting characteristics obtained for a three-layer printed PEDOT:PSS thin film with polar solvent coating were resistivity of 1.49 × 10-3 Ω·cm and transmittance of 84.6%. However, we found that the surface condition changed depending on the processing method, affecting the rate of visible light transmittance.

Effects on p-type buffer layers for semitransparent organic photovoltaics using indium zinc oxide transparent electrode

The present study used transparent conductive oxide films as the top electrode of semitransparent organic photovoltaic (ST-OPV) cells. Indium zinc oxide (IZO) was fabricated by a facing direct current magnetron sputtering method for the top electrode of ST-OPV cells with an inverted structure, and then, the effect of selecting a p-type buffer material applicable to IZO films was investigated. Three kinds of p-type buffer materials were examined, namely, molybdenum trioxide (MoO3), tungsten trioxide-nanoparticles (WO3-NPs), and dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HATCN). The MoO3-, WO3-, and HATCN-based cells yielded power conversion efficiencies (PCEs) of 4.02%, 3.60%, and 3.14%, respectively. After optimization of MoO3 thickness, the 15 nm thick MoO3-based cell reached a PCE of 4.84% and a transmittance of 19.9% at a wavelength of 550 nm.

Use of AC Faraday rotation as a complementary technique in material characterization

Magnetic measurements like Hall Effect, etc. have a long history of providing useful information related to material characterization. Here, we study glasses using a very sensitive AC Faraday rotation (FR) setup to show that magneto-optic techniques can also be utilized to study types of samples that are not necessarily known for their magnetic response. Samples included in this study are widely used in technological and research applications ranging from microscopy to solar cell applications. The experimental setup employs a stabilized He-Ne lase (633 nm) along with AC magnetic field that enables lock-in detection. We investigate a series of glass samples that include borosilicate glass (BSG) and quartz subjected to UV treatment and glass with transparent conducting oxide films (TCO). The TCO samples include the more widely used Indium Tin Oxide (ITO) and the relatively newer Fluorine doped Tin Oxide films, usually referred to as FTO. Various other measurements like absorbance, four-point probe, and ellipsometry have been conducted on these samples as well. We mention the results of these measurements in conjunction with FR measurements, where needed. This work is focused on reporting novel results. A much more comprehensive manuscript is under preparation that explores the deeper connections between FR and the above-mentioned measurements.

Investigation of thermal stability, optical properties, phase and chemical composition of transparent conductive tin oxide films deposited by pyrolytic method on silica float glass

The object of research is transparent conductive coating based on fluorine doped tin oxide deposited on silica float glass by the pyrolytic method. However, both in the manufacturing process of such a coating and in the process of its operation, degradation of its electrically conductive properties is observed. This may be due to changes in the structure of the coating under the influence of certain technological and operational factors, namely: process temperature, holding time, gas environment during the application and operation of a transparent electrically conductive coating. Studies have confirmed a significant increase in electrical conductivity. They also found a slight decrease in the transmittance of transparent oxide-tin films obtained with the introduction of ammonium fluoride as a dopant during the pyrolysis of 1M alcohol solutions of Sn2+ and Sn4+chlorides and are widely used as precursors for the content of such coatings. So, with a ratio of Sn4+/F=10 in working solutions, a minimum of specific surface resistance was fixed at 32 Ohm/m2. At the same time, a decrease in the value of the averaged transmittance in the optical wavelength range of 0.2-6.0 μm by 51 %, and in its visible part (0.4-0.8 μm) by 11 %. It is shown that thermal degradation of the coating is a significant factor in increasing the resistance values both in the technological process and during operational impacts. The results obtained indicate that reheating to temperatures above 450 °C leads to the appearance of the phenomenon of thermal degradation of the electrically conductive properties of the coating. So, during a 1-hour exposure at a temperature of 550 °C, the increase in specific surface resistance increases by 2 times and is fixed at 68 Ohm/m2 after complete cooling. Repeated heating cycles with the indicated parameters lead to a significantly lesser effect, which may indicate stabilization of the processes that occur during thermal destruction of the electrically conductive coating.

Optically Transparent Metamaterial Absorber Using Inkjet Printing Technology.

An optically transparent metamaterial absorber that can be obtained using inkjet printing technology is proposed. In order to make the metamaterial absorber optically transparent, an inkjet printer was used to fabricate a thin conductive loop pattern. The loop pattern had a width of 0.2 mm and was located on the top surface of the metamaterial absorber, and polyethylene terephthalate films were used for fabricating the substrate. An optically transparent conductive indium tin oxide film was introduced in the bottom ground plane. Therefore, the proposed metamaterial absorber was optically transparent. The metamaterial absorber was demonstrated by performing a full-wave electromagnetic simulation and measured in free space. In the simulation, the 90% absorption bandwidth ranged from 26.6 to 28.8 GHz, while the measured 90% absorption bandwidth was 26.8–28.2 GHz. Therefore, it is successfully demonstrated by electromagnetic simulation and measurement results.

Effect of oxygen stoichiometry on the structure, optical and epsilon-near-zero properties of indium tin oxide films.

Transparent conductive oxide (TCO) films showing epsilon near zero (ENZ) properties have attracted great research interest due to their unique property of electrically tunable permittivity. In this work, we report the effect of oxygen stoichiometry on the structure, optical and ENZ properties of indium tin oxide (ITO) films fabricated under different oxygen partial pressures. By using spectroscopic ellipsometry (SE) with fast data acquisition capabilities, we observed modulation of the material index and ENZ wavelength under electrostatic gating. Using a two-layer model based on Thomas-Fermi screening model and the Drude model, the optical constants and Drude parameters of the ITO thin films are determined during the gating process. The maximum carrier modulation amplitude ΔN of the accumulation layer is found to vary significantly depending on the oxygen stoichiometry. Under an electric field gate bias of 2.5 MV/cm, the largest ENZ wavelength modulation up to 27.9 nm at around 1550 nm is observed in ITO thin films deposited with oxygen partial pressure of P O 2 =10 Pa. Our work provides insights to the optical properties of ITO during electrostatic gating process for electro-optic modulators (EOMs) applications.

Impacts of preparation conditions on photoelectric properties of the ZnO:Ge transparent conductive thin films fabricated by pulsed laser deposition

Transparent conducting oxide (TCO) thin film is a key component of photoelectric devices for extensive applications. Exploring new TCO films with high electronic conductivity, high transmittance and low cost is urgently required. Here, the wurtzite structured Ge-doped ZnO thin films were deposited on the glass substrates by using a pulsed laser deposition method. The effects of Ge-doping concentration, glass substrate temperature and oxygen partial pressure on crystallinity, surface morphology, electrical conductivity and visible light optical transmittance of the thin films were studied systematically. It is revealed that the preferred orientation of the film can be controlled by oxygen partial pressure. Under the optimized deposition conditions of Ge-doping amount of 2.0 at.%, glass substrate temperature of 300 °C and oxygen partial pressure of 1.5 Pa, it was found that the prepared ZnO:Ge thin films with a thickness of 95 nm could display an electrical resistivity as low as 6.10 × 10−4 Ω cm and had a high transmittance of 92.3% in the visible region, proving that ZnO:Ge thin film is a promising TCO material.