Cupric Oxide Nanowires Research Articles

Nano‐Patterned CuO Nanowire Nanogap Hydrogen Gas Sensor with Voids

AbstractHydrogen (H2) is increasingly employed in industrial applications, such as developing hydrogen fuel cells for vehicles and power plants. However, H2 explodes at a concentration limit of 4%, necessitating the development of ultrasensitive hydrogen sensors capable of early‐stage detection of hydrogen leaks. In this study, nano‐patterned polycrystalline cupric oxide (CuO) nanowire array nanogap gas sensors with voids are fabricated using electron‐beam lithography and ex situ oxidization by annealing, which could detect 5 ppb H2 and show response and recovery times of less than 10 s without a baseline shift. Combining a pre‐H2 annealing process in Ar/H2 for Cu nanowires and a low‐rate oxidation process enhances the crystallinity of CuO nanowires, facilitating the preparation of polycrystalline CuO nanowires with voids, which is a significantly practical approach for the improvements of gas sensing properties. Response and recovery times of <10 s can be obtained for a gap separation of ≈30 nm. These improvements are discussed based on a high electric field of ≈1.3 MV cm−1. The relationship between the normalized response and H2 concentration is discussed based on the power law. This paper presents highly reliable and fast H2 sensors without a baseline shift to meet the demands of the hydrogen industry.

Thermal oxidation CuO nanowire gas sensor for ozone detection applications

In this study, cupric oxide nanowires (CuO NWs) on patterned interdigitated electrodes (PIEs) used as ozone (O3) gas sensors, were successfully fabricated using thermal oxidation and the microelectromechanical systems (MEMS) technique. After the thermal oxidation process, CuO NWs with different heights and densities were fabricated using a pure copper seed layer with a thickness ranging from 0.5 μm to 2 μm. In this experiment, a low temperature, low concentration, and repeatable CuO NWs gas sensor was fabricated, which can detect O3 gas at a low concentration of 50 ppb and low temperature of 100°C with a high sensor response (40%). The concentration response of this gas sensor shows an increasing linear trend, with an increase of O3 concentration in the range of 50 ppb - 300 ppb. Additionally, the results indicated that this CuO NWs gas sensor is more selective for O3 than CO, CO2, C2H5OH, C3H6O, NO2, or NH3. While CuO has been less studied in O3 detection compared with other semiconducting metal oxide materials, CuO NWs show potential applications in gas sensing devices for low-temperature and low-concentration O3 environmental monitoring.

Size-Dependent Thresholds in CuO Nanowires: Investigation of Growth from Microstructured Thin Films for Gas Sensing.

An experimental characterization of cupric oxide nanowire (CuO NW) growth from thermally oxidized, microstructured Cu thin films is performed. We have systematically studied the influence of the thickness and dimension of Cu layers on the synthesis of CuO NW. The objective was to determine the optimum Cu geometries for increased CuO NWs growth to bridge the gap between adjacent Cu structures directly on the chip for gas sensing applications. Thresholds for CuO-NW growth regarding film thickness and lateral dimensions are identified based on SEM images. For a film thickness of 560 nm, NWs with lengths > 500 nm start to grow from the edges of Cu structures with an area ≥ 4 µm2. NWs growing from the upper surface were observed for an area ≥ 16 µm2. NW growth between adjacent thermally oxidized thin films was analyzed. The study provides information on the most relevant parameters of CuO NWs growth, which is mandatory for integrating CuO NWs as gas sensor components directly on microchips. Based on this result, the gap size of the structure was varied to find the optimum value of 3 µm.

Pt single-atom electrocatalysts at Cu2O nanowires for boosting electrochemical sensing toward glucose

In electrochemical biosensors, rational design and synthesis of high-performance electrochemical glucose sensors based on emerging single-atom catalysts (SACs) are paramount. Herein, a facile approach is proposed for dispersing single-atom doping of cuprous oxide (Cu2O) nanowires with Pt on a copper foam substrate (Pt1/Cu2O@CF) via the electrochemical deposition process. The specific nanostructure of the single-atom catalyst has been elaborately revealed with the aid of atomic resolution scanning transmission electron microscopy (STEM) and X-ray absorption fine structure spectroscopy (XAS). The as-fabricated Pt1/Cu2O@CF biosensor with satisfactory scalability exhibits a low limit of detection (1 μM), ultrahigh sensitivity (31.55 mA mM−1 cm−2), excellent selectivity, and robust reliability toward glucose. The first principles simulations reveal that Pt SAC is beneficial to the adsorption of glucose on the surface and further facilitates the electron transfer for the deprotonation process, resulting in high glucose sensing performance. This work sheds light on the applications of SACs for designing ultrasensitive electrochemical biosensors.

Transition metal (Fe, Co, Ni)-doped cuprous oxide nanowire arrays as self-supporting catalysts for electrocatalytic CO2 reduction reaction to ethylene

The transition metal (Fe, Co, Ni)-doped cuprous oxide (Cu2O) nanowire arrays on Cu mesh (CM) (M-Cu2O@CM, M = Fe, Co, Ni) are successfully synthesized for the electrocatalytic CO2 reduction reaction (CO2RR) to ethylene (C2H4) through the simple calcination and impregnation-exchange methods. Systematic characterizations have demonstrated that the Ni/Co doping in Cu2O@CM is conducive to stabilizing the Cu+ sites due to the electron transfer from Cu2O to Ni/Co, while the Fe doping has the opposite effect. Consequently, they show the different electrocatalytic performances of Ni-Cu2O@CM > Co-Cu2O@CM > Cu2O@CM > Fe-Cu2O@CM for CO2RR to C2H4 in an H-cell. Among them, Ni-Cu2O@CM exhibits the ∼2.0-fold faradaic efficiency for C2H4 (58.2 % vs. 28.7 %) and the ∼2.5-fold current density (−37.6 vs. −15.0 mA·cm−2) at −1.1 V vs. RHE, as compared with Cu2O@CM. Further experiments reveal that during the electrocatalytic CO2RR, the Ni-Cu2O@CM can generate more *CO, which promotes the C–C coupling reaction. The activity of Co-Cu2O@CM is lower than Ni-Cu2O@CM because of the strong adsorption of *COOH, while the Fe-Cu2O@CM even exhibits a lower activity than Cu2O@CM. This work provides an insight into the effect of transition metal-doped Cu2O array on the electrocatalytic CO2RR to C2H4 products.

(Invited) Coupling Metal-Organic Framework with Oxide Photocatalyst for Selective Photoredox Reactions

Oxide photocatalyst is one of the major groups of photoactive semiconductors capable of facilitating useful photoredox reactions for a variety of energy and environmental-related applications. The intrinsic optical and electronic properties of oxide photocatalysts encounter a number of limitations. Often, the wide band gap and inferior photoexcited charge transportation within oxide semiconductors are highlighted. Wide band gap limits the light absorption while inadequate charge transport properties such as low charge mobility and short lifetime can only afford mild photoactivities. Strategies have been formulated to improve the performance of these semiconductors in order to bridge the gap for practical use. Among many existing strategies, coupling oxide photocatalysts with metal-organic framework (MOF) has gained attention in the community as one potential method to improve performance (e.g. higher light absorption, better product yield, prolonged stability and etc). Attaching photoactive MOFs onto or “doping” metallic element into oxide photocatalyst may extend the light absorption of the composite materials. Improved product yield is, more often, attributed to the adsorption capacity of MOFs towards reactant, which bring about the localised concentration of reactants adjacent to active sites of photocatalyst. Encapsulation of oxide photocatalyst by MOFs can suppress the undesirable side reactions (such as preventing Cu2O from direct contact with moisture) to prolong the stability of oxide photocatalyst.In this presentation, in addition to the above mentioned advantages of MOFs, the role of MOFs in tuning the selectivity of product formation will also be examined and discussed. Figure 1 shows an example of improved selective oxidation of ethanol to form acetaldehyde using ZIF-8 encapsulated ZnO. Selectivity towards acetaldehyde has been improved from ~79% to ~92% with stable photocatalytic activity.1 In another work, Cu2O covered by Cu-MOF has afforded selective CO2 photoreduction to CH4.2 We believe there is charge interaction between the oxide photocatalyst and the adjacent MOF structure. Transfer of photoexcited electrons from the conduction band of Cu2O to the LUMO level of non-excited wide band gap Cu-MOF has been indicated using time-resolved photoluminescence. Because photocatalytic reactions are the results of electron transfer between photocatalyst and reactants, the presence of photocharge interplay between oxide photocatalyst and MOFs may provide new room for exploration as it has demonstrated significant influence in the selectivity of product formation. Figure 1. Example of improved product selectivity by incorporating MOFs to oxide photocatalyst. The left figure indicates the improved formation of acetaldehyde from photocatalytic ethanol oxidation. The right figure shows the reasonable stability of the MOF-oxide photocatalyst under illumination. Reference: H. Wu, T. H. Tan, R. Liu, H. -Y. Hsu, Y. H. Ng, Selective Ethanol Oxidation to Acetaldehyde on Nanostructured Zeolitic Imidazolate Framework-8-wrapped ZnO Photothermocatalyst Thin Films, Solar RRL 2021, 5, 2000423.H. Wu, X. Y. Kong, X. Wen, S. –P. Chai, E. C. Lovell, J. Tang, Y. H. Ng, Metal-Organic Framework Decorated Cuprous Oxide Nanowires for Long-lived Charges Applied in Selective Photocatalytic CO2 Reduction to CH4. Angew. Chem. Int. Ed. 2021, 60, 8455-8459. Figure 1

Formation of CuO whiskers and facet-controlled oxidation during the oxidation of Au-Cu nanoparticles fabricated by solid-state dewetting

The fabrication of cupric oxide (CuO) nanowires from Cu particles via thermal oxidation provides a simple and scalable method to produce hierarchical structures. A stress-induced growth mechanism is believed to account for the nanowire formation while a slow oxidation rate is favored to sustain the driving force. Here, CuO whiskers are grown from Au-Cu nanoparticles because the formation of Au-Cu phases decreases the Cu diffusion rate and in turn slows down the oxidation rate. The driving force for the whisker growth is attributed to the compressive stress imposed by the CuO shell on the Au-Cu core, which is induced by the significantdifference in their linear thermal expansion coefficients. The contribution of the compressive stress is proved by the calculation. Moreover, preferred oxidation is observed and it is related to the crystalline structures of different facets existing on the surface of Au-Cu nanoparticles. The more compact the plane, the slower the diffusion rate through the plane, resulting in the formation of thinner CuO on the relevant facet. The results open a cost-effect way to fabricate hybrid nanostructures consisting of Cu-based core–shell nanoparticles attached with CuO whiskers and bring new insights into the oxidation behaviors of Cu on different crystal planes.

Triboelectric nanogenerator based on direct image lithography and surface fluorination for biomechanical energy harvesting and self-powered sterilization

Due to the high electric output, triboelectric nanogenerators (TENG) have gained extensive attention in recent years for their abilities to power the wearable and portable electronic devices. Surface charge density and effective contact area are pivotal for the electric output of the TENG. In this work, the maskless direct image lithography (DIL) method with high precision and rapid prototyping was used to fabricate the polyurethane (PU) layers with surface microcones within 3 min for increasing the contact electrification area. After chemically modified with trichloro (1 H,1 H,2 H,2 H-perfluorooctyl) silane (FOTS) vapor, the contact area further increases accompanying with the enlarged electron affinity difference because of the roughened morphology in micro-nanoscale and the introduced surface fluorine. The TENG based on PU and fluorinated polyurethane (F-PU) layer with microcones can achieve a high current of 22 μA, which is 5 times higher than that of the flat PU and F-PU layers. The microcones, surface roughened morphology and fluorine on the microcones have conjunct effects on the enhancement of electric output. Moreover, because of the customizability of DIL method and the prominent stability and favorable flexibility of PU and F-PU layers, the TENG can be fabricated into different shapes to harvest mechanical energy from various human motions. Furthermore, when the TENG was connected with the cuprous oxide (Cu2O) nanowire electrode and served as the electric supply, the antibacterial and antifungal properties of the nanowire show obvious enhancement. Thus, this work provides a rapid and effective way to enhance the output of TENG from perspectives of surface microstructure design without any templates.

Formation of core-shell nanostructure through wrapping of cuprous oxide nanowires by hydrogen titanate nanotubes

Recent developments of heterojunction-based devices through bottom-up approach such as sensors, light-emitters, energy generation and storage have emerged with great interest due to their wide range of operation and application related flexibilities. This work demonstrates how as-grown hydrogen titanate nanotubes (HTNT) bend and wrap on pristine curpous oxide nanowires (CONW) when mixed together. The unique architecture of wrapping followed by junction formation enhances the active surface area and reduces the contact resistance between the adjacent CONW and HTNT. Such a film upon further ion beam irradiation produces a large-scale network of hetero- and homo-junctions. This newly formed thin film surface upon irradiation shows strong water repelling properties and higher electrical conductivity. The wrapping mechanism, bond formation and the change of conductivity are explained using first principles calculations. The ion beam modifications and large-scale joining are predicted by state-of-the-art TRI3DYN simulation, which is based on binary collision approximation and simulated in a Monte Carlo approach. The observed wrapping and heterojunction are expected to provide excellent mechanical strength and flexibility, which are suitable for fabrication of flexible electronic devices.

Zn–Co-MOF on solution-free CuO nanowires for flexible hybrid energy storage devices

Pouch-type supercapacitor was developed by employing flexible Zn–Co-metal organic framework (MOF)@CuO and porous reduced graphene oxide as active electrodes. The flexible Zn–Co-MOF@CuO was fabricated by a facile two-step strategy. In the first step, Cu mesh was oxidized to cupric oxide (CuO) by a solution-free treatment. In the second step, Zn–Co-MOF was deposited on CuO scaffold through a solvothermal treatment. The as-prepared integrated Zn–Co-MOF@CuO exhibited excellent flexibility at different bending angles. The flexible Zn–Co-MOF@CuO displayed excellent electrochemical activity during three-electrode testing due to the merits of high electrical conductivity and an existence of p-n heterojunction between CuO and Zn–Co-MOF. The as-fabricated pouch supercapacitor yielded a high energy density of 41 W h kg−1 at a current density of 1 A g−1 and an excellent cycling stability of 97% after 20,000 cycles. Structural and superior electronic properties of Zn–Co-MOF@CuO were further verified through first principles calculations based on density functional theory (DFT), which perfectly supported the experimental results. The excellent electrochemical attributes of the flexible pouch supercapacitor show immense promise for next-generation electrochemical energy storage devices.

A vertical CuO-NWS/MEMS NO2 gas sensor that is produced by sputtering

This study produces cupric oxide (CuO) nanowires (NWs) using RF sputtering, and integrated CuO NWs in a micro electron mechanical systems (MEMS) structure to form a CuO-NWS/MEMS gas sensor. The XRD pattern shows a preferred (002) orientation of the CuO NWs. The CuO-NWS grows vertically on the MEMS structure and a competitive growth model is illustrated. It is found that the CuO-NWs/MEMS gas sensor has a higher selectivity to NO2 compared with CO, CO2, NH3 and SO2. In long term measurement, the average sensor response is about 50.1% with an inaccuracy of 3% at the temperature of 119 ℃ and the NO2 concentration of 500 ppb. These results show that the CuO-NWs/MEMS sensor with sputtering method is stable and reproducible in NO2 gas sensing.

Thermal oxidation impact on the optoelectronic and hydrogen sensing properties of p-type copper oxide thin films

The paper presents the results of the investigation of the post-process annealing effect on selected properties of copper oxide thin films deposited by magnetron sputtering. It was found that the prepared thin films were nanocrystalline with the crystallite size smaller than 20 nm. Annealing at temperatures of 200 °C, 300 °C and 350 °C caused metallic copper oxidation to copper(I) oxide and then to copper(II) oxide. As-deposited and annealed at 200 °C thin films were composed of Cu and Cu2O. Copper(I) oxide transformation into CuO started at 300 °C, while the thin film annealed at 350 °C consisted of a single CuO phase. Scanning electron microscopy imaging revealed that annealing of the as-deposited thin films caused gradual formation of cupric oxide nanowires. Optimum annealing temperature for nanowires growth was 350 °C. X-ray photoelectron spectroscopy showed that the surface of the as-deposited thin films was oxidized to Cu2O and CuO, while in the case of annealed films it was completely oxidized to CuO. Thermal treatment also contributed to the increase in coating transparency in the infrared range. The transmission coefficient at 1500 nm of the thin film annealed at 350 °C was equal to 68. The resistivity of the as-deposited copper oxide thin film was equal to 1.9•10−3 Ωcm, while the highest resistivity of the annealed thin films was equal to 32 Ωcm for the coating annealed at 200 °C. A further increase in the annealing temperature resulted in a slight decrease in the resistivity value. Based on Seebeck coefficient measurements, it was found that all coatings were characterized by p-type conductivity. Additionally, sensing properties toward hydrogen were examined. The best sensor response exceeding 13 was observed for the thin film annealed at 200 °C.

Structural and Compositional Investigations on the Stability of Cuprous Oxide Nanowire Photocathodes for Photoelectrochemical Water Splitting.

Cuprous oxide (Cu2O) is a promising photocathode material for photoelectrochemical (PEC) water splitting. Recently, the PEC performances of Cu2O-based devices have been considerably improved by introducing nanostructures, semiconductor overlayers, and hydrogen evolution reaction (HER) catalysts. However, Cu2O devices still suffer from poor stability in aqueous solution, especially in strong acidic or alkaline conditions, despite the use of an intrinsically stable oxide overlayer as a protection layer. Thus, it is essential to fully understand the stability of the entire Cu2O photocathodes in these conditions for establishing suitable protection strategies to achieve durable PEC water splitting. In this work, the stability of bare and protected Cu2O nanowire (NW) photocathodes was evaluated in detail using microscopy techniques and compositional analyses. The insights gained in this work will guide the design and synthesis of durable photoelectrodes for PEC water splitting.

Anomalous diameter dependent electrical transport in individual CuO nanowire

Cupric oxide (CuO) nanostructure arrays have been extensively investigated for solar energy harvesting, electrochemical energy storage, chemical sensing, field-effect transistors, etc. Although most of these applications depend on the collective behavior of an array of such structures, analysis of electrical transport in a single nanostructure, which are the building blocks, is essential for understanding both the fundamental aspects and device performance. Here we report the electrical conduction mechanism in thermally grown single CuO nanowire (NW), which reveals that the current density has an anomalous dependence on the diameter of the NWs—decreasing with an increase in diameter. An analysis of the electrical behavior at room temperature shows that the current density in CuO NWs has different slopes in different regions of the applied bias indicating distinct types of charge transport, which are characterized as near Ohmic (lower voltage), trap controlled, and space charge limited conduction (higher applied voltage). Further, the trap density and activation energy are calculated from the temperature-dependent current density data, which shows higher values (9.38 × 1015cm−3, 79.4 meV) in thicker NWs compared to that in the thinner ones (3.96 × 1015 cm−3, 63.9 meV). Investigation of the NWs with Raman and photoluminescence spectra establishes the presence of Cu2O phase in thicker NWs, which act as hole traps to hinder the charge transport in p-type CuO and resulting in lower conductivity at higher diameters. This study helps to design and fabricate prototype nanodevices with desired conductivity based on CuO NWs.

Reduced graphene oxide as protective material on cuprous oxide nanowire; the challenges and proposal for improvement in photoelectrochemical application

Abstract In this study, the protection of Cu2O nanowire (NW) against photocorrosion using reduced graphene oxide (rGO) through annealing has proven challenging. The rGO was incapable of forming conformal passivation around Cu2O NW strands, exposing Cu2O NW to a dramatic photocorrosion. The result validated the hypothesis, which underlines the possibility of carbon decomposition from rGO into CO or CO2 gases, distorting the integrity of rGO sheets as a protective coating. Therefore, the current study proposes the carbon coating using the sputtering technique to produce a conformal coating around the NW strand, which should be the ideal protection strategy.

Synthesis of Cu2O-Modified Reduced Graphene Oxide for NO2 Sensors.

Nowadays, metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted significant research attention for gas sensing applications. Herein, a novel composite material is synthesized by combining two p-type semiconductors, i.e., Cu2O and rGO, and a p-p-type gas sensor is assembled for NO2 detection. Briefly, polypyrrole-coated cuprous oxide nanowires (PPy/Cu2O) are prepared via hydrothermal method and combined with graphene oxide (GO). Then, the nanocomposite (rGO/PPy/Cu2O) is obtained by using high-temperature thermal reduction under Ar atmosphere. The results reveal that the as-prepared rGO/PPy/Cu2O nanocomposite exhibits a maximum NO2 response of 42.5% and is capable of detecting NO2 at a low concentration of 200 ppb. Overall, the as-prepared rGO/PPy/Cu2O nanocomposite demonstrates excellent sensitivity, reversibility, repeatability, and selectivity for NO2 sensing applications.

Metal-Organic Framework Decorated Cuprous Oxide Nanowires for Long-lived Charges Applied in Selective Photocatalytic CO2 Reduction to CH4.

Improving the stability of cuprous oxide (Cu2 O) is imperative to its practical applications in artificial photosynthesis. In this work, Cu2 O nanowires are encapsulated by metal-organic frameworks (MOFs) of Cu3 (BTC)2 (BTC=1,3,5-benzene tricarboxylate) using a surfactant-free method. Such MOFs not only suppress the water vapor-induced corrosion of Cu2 O but also facilitate charge separation and CO2 uptake, thus resulting in a nanocomposite representing 1.9 times improved activity and stability for selective photocatalytic CO2 reduction into CH4 under mild reaction conditions. Furthermore, direct transfer of photogenerated electrons from the conduction band of Cu2 O to the LUMO level of non-excited Cu3 (BTC)2 has been evidenced by time-resolved photoluminescence. This work proposes an effective strategy for CO2 conversion by a synergy of charge separation and CO2 adsorption, leading to the enhanced photocatalytic reaction when MOFs are integrated with metal oxide photocatalyst.

Metal–Organic Framework Decorated Cuprous Oxide Nanowires for Long‐lived Charges Applied in Selective Photocatalytic CO2 Reduction to CH4

AbstractImproving the stability of cuprous oxide (Cu2O) is imperative to its practical applications in artificial photosynthesis. In this work, Cu2O nanowires are encapsulated by metal–organic frameworks (MOFs) of Cu3(BTC)2 (BTC=1,3,5‐benzene tricarboxylate) using a surfactant‐free method. Such MOFs not only suppress the water vapor‐induced corrosion of Cu2O but also facilitate charge separation and CO2 uptake, thus resulting in a nanocomposite representing 1.9 times improved activity and stability for selective photocatalytic CO2 reduction into CH4 under mild reaction conditions. Furthermore, direct transfer of photogenerated electrons from the conduction band of Cu2O to the LUMO level of non‐excited Cu3(BTC)2 has been evidenced by time‐resolved photoluminescence. This work proposes an effective strategy for CO2 conversion by a synergy of charge separation and CO2 adsorption, leading to the enhanced photocatalytic reaction when MOFs are integrated with metal oxide photocatalyst.

Cupric oxide nanowire photocathodes stabilized by modification with aluminum

The use of sunlight for photoelectrochemically splitting water into hydrogen and oxygen has aroused great interest in the last decades. Photocathode materials based on cupric oxide (CuO) are promising for large-scale, widespread photoelectrochemical water splitting due to the high Earth-abundance of copper, suitable band gap, and favorable band alignment for hydrogen generation. The main challenge for the development of practical CuO photocathodes is to enhance stability against photocorrosion, together with increasing the efficiency of solar hydrogen evolution. In this work, stable CuO nanowire photocathodes are synthetized in a straightforward and scalable way by electrodeposition followed by chemical oxidation and thermal treatment. Subsequently, the electrodes are modified with aluminum following two different strategies: (i) adsorption of aluminum from an Al acetylacetonate solution or (ii) drop-casting of a solution containing Al nitrate. In both cases, a thermal treatment is applied after Al addition. The stability of CuO nanowires (measured as the percent of the initial photocurrent retained after 20 min of continuous illumination at −0.4 V vs. Ag/AgCl) is enhanced from 2% up to 80%. The amount of aluminum needed to modify cupric oxide is very low in both strategies, indicating that Al operates at the surface level. Admittedly, these modifications improve stability at the expense of photocurrent. To palliate this, the addition of co-catalysts should be addressed in the future.

Preparation of copper nanowires conductive films by using cuprous oxide nanowire as template

Polypyrrole-coated cuprous oxide nanowires with a large aspect ratio were prepared via the hydrothermal reduction of copper acetate with pyrrole. Initially, the nanowires were transferred onto a glass substrate by suction filtration and embossing. A copper nanowire conductive film can then be obtained after high temperature annealing reduction and transferred onto a flexible substrate via hot press transfer. The product was analyzed via X-ray powder diffractometry, scanning electron microscopy, and transmission electron microscopy. The visible light transmittance and the surface resistance of the sample were measured by employing an ultraviolet-visible spectrophotometer and a four-probe surface resistance meter, respectively. The effects of the annealing temperature, of the time, the dispersion of the square resistance, and the transmittance of the conductive film were investigated. The results show that the conductive film exhibits a high visible light transmittance (82%) and a low sheet resistance (62 Ω/sq) upon annealing at 700 °C for 300 seconds.