Effect of the heat treatment on the infrared emissivity of indium tin oxide (ITO) films

Indium tin oxide (ITO) films were deposited on glass substrates at temperatures ranging from 100 °C to 400 °C by direct current magnetron sputtering. The mean infrared emissivities at the waveband of 8-14 μm were measured in process of heating and cooling between room temperature and 350 °C. Microstructure and phases of ITO films before (Group A) and after (Group B) heat treatment were characterized by SEM and XRD, respectively. Electrical properties were characterized with a four-point probe method and by Hall measurement system. During heat treatment, the infrared emissivity of the film increases with the increase of temperature, and decreases with the decrease of temperature. While, the infrared emissivity of the films decreases slightly around 250 °C in heating process. On the other hand, after heat treatment, the crystalline phases of the films have no obvious change. However, both the resistivity and the infrared emissivity of all films decrease.     

The effect of carbon contamination and argon ion sputtering on the work function of chlorinated indium tin oxide

The work function of indium tin oxide (ITO) was increased by treating ITO with dichlorobenzene with UV light. Carbon contamination of the Cl-ITO was measured using X-ray Photoelectron Spectroscopy (XPS) and argon ion sputtering was used to remove the carbon from the surface. It was found that the carbon contamination from residual dichlorobenzene significantly lowered the work function of the ITO and after argon ion sputtering the work function increased to 5.8 eV. It was found that chlorination of ITO occurs after more than 6 min of UV exposure. Further sputtering of ITO resulted in the removal of the functionalized chlorine, the introduction of argon ion contaminants on the ITO decreases its work function.     

Pulsed laser ablation of indium tin oxide in the nano and femtosecond regime: Characterization of transient species

Tin doped indium oxide (ITO) is a n-type highly degenerate, wide band-gap semiconductor that is extensively used for many engineering applications. Pulsed laser ablation of indium tin oxide in the nano and femtosecond regime has been performed in our laboratory. Plume diagnostics has been carried out by means of a fast Intensified Coupled Charge Device (ICCD) camera. Optical emission spectroscopy has been applied to characterize the transient species produced in the nano and femtosecond regime. The time evolution of emission lines, in the femto and nanosecond regime, have been compared and discussed. In the mass spectrometry, of the ionized species, the presence of mixed metal oxide clusters has been detected. This fact is an indication that chemical reactions can occur during the plasma expansion or on the ITO surface.     

Enhanced electrical stability of flexible indium tin oxide films prepared on stripe SiO2 buffer layer-coated polymer substrates by magnetron sputtering

The electrical stability of flexible indium tin oxide (ITO) films fabricated on stripe SiO₂ buffer layer-coated polyethylene terephthalate (PET) substrates by magnetron sputtering was investigated by the bending test. The ITO thin films with stripe SiO₂ buffer layer under bending have better electrical stability than those with flat SiO₂ buffer layer and without buffer layer. Especially in inward bending text, the ITO thin films with stripe SiO₂ buffer layer only have a slight resistance change when the bending radius r is not less than 8 mm, while the resistances of the films with flat SiO₂ buffer layer and without buffer layer increase significantly at r = 16 mm with decreasing bending radius. This improvement of electrical stability in bending test is due to the small mismatch factor α in ITO-SiO₂, the enhanced interface adhesion and the balance of residual stress. These results indicate that the stripe SiO₂ buffer layer is suited to enhance the electrical stability of flexible ITO film under bending.     

Reduced graphene oxide field-effect transistor with indium tin oxide extended gate for proton sensing

In this study, the reduced graphene oxide field-effect transistor (rGO FET) with indium tin oxide (ITO) extended gate electrode was demonstrated as a transducer for proton sensing application. In this structure, the proton sensing area of the ITO extended gate electrode is isolated from the active area of the rGO FET. The proton sensing properties based on the rGO FET transducer were analyzed. The rGO FET device with encapsulation by a tetratetracontane (TTC) layer showed good stability in electrolytic solutions. The device showed an ambipolar behavior with shifts in Dirac point as the pH of the electrolyte is varied. The pH sensitivity based on the Dirac point shift as a sensing parameter was about 43–50 mV/pH for a wide range of pH values from 2 to 12. The ITO extended gate rGO FET may be considered a potential transducer for sensing of H⁺ in electrolytes. Its sensing area can be modified further for various ions sensing applications.     

Studies on the electrochemiluminescent behavior of luminol on indium tin oxide (ITO) glass

The electrochemiluminescence (ECL) of luminol on indium tin oxide (ITO) glass was high even under a low potential around 0.4-0.5 V, which was quite different from other electrodes such as platinum. ITO nanoparticles were synthesized and used in the research on ITO glass in the ECL process. A static interaction between ITO and luminol is confirmed from UV-vis and fluorescence spectra. Then the ECL enhancement can be supposed to originate from the adsorption of luminol on ITO, which facilitated luminol’s oxidization to the excited state, giving out ECL. On the other hand, ITO can catalyze the generation of reactive oxygen species (ROSs), similar to some other nanomaterials, which also favored the ECL enhancement of luminol.     

后退火处理对铟锡氧化物表面等离激元共振特性的影响

近年来,表面等离激元光子学发展迅速,并取得了众多新成果.重掺杂半导体材料的表面等离激元共振性质的研究,也得到了人们越来越多的关注.本文通过纳米球刻印技术制备准三维二氧化硅纳米球阵列,在阵列上沉积铟锡氧化物薄膜,通过不同条件下的后退火处理改变铟锡氧化物薄膜的载流子浓度和载流子迁移率,并研究随着材料性质的改变其相应表面等离激元共振特性的变化规律.结果表明：退火处理均使铟锡氧化物薄膜的晶粒长大,光学透过率增加;在空气中退火会导致铟锡氧化物薄膜的载流子浓度减少,其表面等离激元共振峰红移;而真空退火则使铟锡氧化物薄膜的载流子浓度增加,共振峰蓝移.这些研究结果可为后续铟锡氧化物表面等离激元材料及器件的研究提供科学依据和实际指导.     

Surface modification of indium tin oxide films by amino ion implantation for the attachment of multi-wall carbon nanotubes

Amino ion implantation was carried out at the energy of 80 keV with fluence of 5 × 10¹⁵ ions cm⁻² for indium tin oxide film (ITO) coated glass, and the existence of amino group on the ITO surface was verified by X-ray photoelectron spectroscopy analysis and Fourier transform infrared spectra. Scanning electron microscopy images show that multi-wall carbon nanotubes (MWCNTs) directly attached to the amino ion implanted ITO (NH₂/ITO) surface homogeneously and stably. The resulting MWCNTs-attached NH₂/ITO (MWCNTs/NH₂/ITO) substrate can be used as electrode material. Cyclic voltammetry results indicate that the MWCNTs/NH₂/ITO electrode shows excellent electrochemical properties and obvious electrocatalytic activity towards uric acid, thus this material is expected to have potential in electrochemical analysis and biosensors.     

Enhancing indium tin oxide (ITO) thin film adhesiveness using the coupling agent silane

The coupling agent γ-mercapto propyl trimethoxy silane (WD-80) was used to enhance the adhesiveness of the indium tin oxide (ITO) thin film, which was prepared on a glass substrate using the sol-gel method. The nano-scratching test, XRD, TEM, SEM, and UV-vis spectrophotometer were employed to examine film adhesion, crystal structure, surface morphology, and transmittance. The results indicated that silane coupling agent, used in low concentration, did not change the film structure but increased the critical load of the film by 49%, from 4.16 mN to 6.20 mN, when the film was peeled off from the substrate. The principle by which the coupling agent works is discussed. In addition to increasing with the light wavelength, the average transmittance of the film in the visible range varied from 78.9% to 83.6%. Moreover, as a function of the WD-80 silane coupling agent, the film exhibited a high smoothness and density due to the orderly arrangement of particles.     

Ellipsometry investigation of the effects of annealing temperature on the optical properties of indium tin oxide thin films studied by Drude-Lorentz model

Float glass substrates covered by high quality ITO thin films (Balzers) were subjected for an hour to single thermal treatments at different temperature between 100 °C and 600 °C. In order to study the electric and optical properties of both annealed and not annealed ITO-covered float glasses, ellipsometry, spectrophotometry, impedance analysis, and X-ray measurements were performed. Moreover, variable angle spectroscopic ellipsometry provides relevant information on the electronic and optical properties of the samples. ITO film is modeled as a dense lower layer and a surface roughness layer. The estimated optical density for ITO and the optical density of the surface roughness ITO layer increases with the annealing temperature. In the near-IR range, the extinction coefficient decreases while the maximum of the absorption in the near UV range shift towards low photon energy as the annealing temperature increases. Spectrophotometry was used to estimate the optical band-gap energy of the samples. The thermal annealing changes strongly the structural and optical properties of ITO thin films, because during the thermal processes, the ITO thin film absorbs oxygen from air. This oxygen absorption decreases the oxygen vacancies therefore the defect densities in the crystalline structure of the ITO thin films also decrease, as confirmed both by ellipsometry and X-ray measurements.     

Application of indium tin oxide (ITO) thin film as a low emissivity film on Ni-based alloy at high temperature

Indium tin oxide (ITO) films as the low emissivity coatings of Ni-based alloy at high temperature were studies. ITO films were deposited on the polished surface of alloy K424 by direct current magnetron sputtering. These ITO-coated samples were heat-treated in air at 600–900 °C for 150 h to explore the effect of high temperature environment on the emissivity. The samples were analyzed by X-ray diffraction (XRD), SEM and EDS. The results show that the surface of sample is integrity after heat processing at 700 °C and below it. A small amount of fine crack is observed on the surface of sample heated at 800 °C and Ti oxide appears. There are lots of fine cracks on the sample annealed at 900 °C and a large number of various oxides are detected. The average infrared emissivities at 3–5 μm and 8–14 μm wavebands were tested by an infrared emissivity measurement instrument. The results show the emissivity of the sample after annealed at 600 and 700 °C is still kept at a low value as the sample before annealed. The ITO film can be used as a low emissivity coating of super alloy K424 up to 700 °C.     

Indium tin oxide sol-gel precursor conversion process using the third harmonics of Nd:YAG laser

We use the third harmonics of Nd:YAG laser (λ = 355 nm) for simultaneous precursor conversion and dopant activation on sol-gel ITO thin films at a laser fluence range of 700-1000 mJ/cm². A minimum resistivity of 5.37 × 10⁻² Ω-cm with a corresponding carrier concentration of 6 × 10¹⁹ cm⁻³ is achieved at laser irradiation fluence of 900 mJ/cm². X-ray photoelectron analysis reveals that extremely high tin concentration of 19.4 at.% and above is presented in the laser-cured ITO thin films compared with 8.7 at.% in the 500 °C thermally cured counterpart. These excess tin-ions form complex defects, which contribute no free carriers but act as scattering centers, causing inferior electrical properties of the laser-cured films in comparison with the thermally cured ones.     

Work function changes and surface chemistry of oxygen, hydrogen, and carbon on indium tin oxide

The surface chemistry of indium tin oxide (ITO) has been investigated with Auger electron spectroscopy (AES) and high resolution electron energy loss spectroscopy (HREELS). A vibrating Kelvin probe (KP) with a graphite reference was used to monitor the absolute work function (Φ) of ITO as a function of chemical modification. The ITO was exposed in situ to molecular hydrogen (H₂), hot-filament-activated oxygen (O₂^*), and hot-filament-activated deuterium (D₂^*). The initial Φ of ITO was determined to be 5.2 eV, and surface chemical changes had strong effects on this value, as seen by KP. Exposure of clean ITO to O₂^* increased Φ to 5.6 eV, but the increase was short-lived. The changes in Φ over time were correlated with the uptake of carbon impurities in ultra high vacuum (UHV), as monitored by AES.

The HREELS of ITO revealed significant hydrocarbon impurities. Chemical reduction of ITO produced a metallic surface and dehydrogenated the adsorbed hydrocarbons. Both re-oxidation of metallic ITO and oxidation of clean ITO temporarily removed adventitious carbon from the surface, but oxidized ITO adsorbed an even larger quantity of carbon over time.     

Plasma-based sputtering of indium tin oxide for the application of photovoltaic cells

Transparent and conducting indium tin oxide (ITO) thin films were deposited on soda lime glass substrates by RF plasma magnetron sputtering at room temperature. The effect of thickness (100, 200 and 300?nm) on the physical (structural, optical, electrical) properties of ITO thin films was investigated systematically. It is observed that with an increase in thickness, the X-ray diffraction data indicate polycrystalline films with grain orientations predominantly along (222) and (400) directions; the average grain size increases from 10 to 30?nm; the optical band gap increases from 3.68 to 3.73?eV and the transmission decrease from 80% to 70% . Four-point probes show a low resistivity (2.4×10^?5?Ω?cm) values for film with a thickness 300?nm. Present work shows that the ITO is a promising transparent conductive oxide material for the solar cell application.     

Electrical and optical properties of indium tin oxide/epoxy composite film

The electrical and optical properties of the indium tin oxide(ITO)/epoxy composite exhibit dramatic variations as functions of the ITO composition and ITO particle size. Sharp increases in the conductivity in the vicinity of a critical volume fraction have been found within the framework of percolation theory. A conductive and insulating transition model is extracted by the ITO particle network in the SEM image, and verified by the resistivity dependence on the temperature.The dependence of the optical transmittance on the particle size was studied. Further decreasing the ITO particle size could further improve the percolation threshold and light transparency of the composite film.     

Attachment of gold nanoparticles onto indium tin oxide surfaces controlled by adding citrate ions in a seed-mediated growth method

A simple approach to control the attachment of gold nanoparticles (AuNPs) onto the indium tin oxide (ITO) surfaces is reported. Adjusting the concentration of trisodium citrate in the Au colloid solution for the seeding process from 1 to 50 mM in the seed-mediated growth method, the dramatic changes in the SEM images and actual color were observed indicating the changes in nanostructures of AuNPs formed on the ITO surfaces. Whereas the attachment of smaller AuNPs with higher density were observed when 25 mM citrate ions were added in the seed solution, larger AuNPs were observed to attach at 50 mM. On the basis of this difference and the surface SEM images observed just after seeding, the roles of citrate ions were discussed. Consequently, it was inferred that the citrate ions affected the growth process as well as the seeding process. The repulsive power expected from the increased negative charges of citrate ions were not significant, but rather the dense attachment was promoted as the peculiar effect of citrate ions. Such control of the AuNPs attachment on ITO would be practically effective because the dense attachment can be performed by just changing the composition of the seed solution.     

On the behavior of a dense indium oxide/yttria-stabilized zirconia electrode

The electrical, structural and electrochemical properties of a dense In₂O₃ layer in contact with a single crystal YSZ electrolyte were studied. As a result of dc and ac investigations, it was found that under anodic polarization the rate of Faraday reaction at the surface of the In₂O₃ electrode is as low as in an ionically blocked electrode. Under cathodic polarization, however, the electrochemical activity of the electrode improves depending on the magnitude of the polarization voltage. Likewise, the electrode polarization resistance decreases after platinum or praseodymium oxide having been deposited on the surface of the In₂O₃ layer. The possible mechanism responsible for such a peculiar behaviour and the limiting step of the electrode reactions are discussed.     

Effect of the duty ratio on the indium tin oxide (ITO) film deposited by in-line pulsed DC magnetron sputtering method for resistive touch panel

The indium tin oxide (ITO) film was deposited on PET (polyethylene terephthalate) film using in-line pulsed DC magnetron sputtering system with different duty ratios. The reverse time and the frequency of pulsed DC power were changed to obtain the different duty ratios. From the electrical and optical properties such as the sheet resistance, resistivity, thickness and transmittance, the pulsed DC sputtered ITO/PET films were also superior to the DC sputtered ITO/PET films. The reverse time had little effect on the properties of the ITO/PET film and the frequency of pulsed DC power had an immerse effect on the properties of the ITO/PET films. The optimal ITO/PET film was obtained when the frequency was 200 kHz, the reverse time was 1 μs, and the duty ratio was about 80%.     

Current-voltage characterization of Au contact on sol-gel ZnO films with and without conducting polymer

This study investigates the current density-voltage (J-V) characteristics of Au/n-type ZnO and Au/polyaniline (PANI)/n-type ZnO devices. ZnO films were prepared by the sol-gel method. For Au/n-type ZnO devices, native defects and impurities resident within the ZnO depletion region contribute to barrier thinning of, carrier hopping across, and tunneling through the Schottky barrier. This leads to the formation of nonalloyed ohmic contacts. However, rectifying junctions were formed on n-type ZnO by employing the simple technique of spin-coating PANI to act as the electron-blocking layer. Our present results suggest that the ZnO depletion region at the PANI/n-type ZnO interface is not the origin of the rectifying behavior of Au/PANI/n-type ZnO contact. In addition, the presence of the built-in potential of Au/PANI/n-type ZnO devices could result in the shift of the J-V curve toward negative voltage. Excellent agreement between simulated and measured data was obtained when the built-in potential was taken into account in the J-V relationship.     

Sputter deposition of indium tin oxide onto zinc pthalocyanine: Chemical and electronic properties of the interface studied by photoelectron spectroscopy

The interface chemistry and the energy band alignment at the interface formed during sputter deposition of transparent conducting indium tin oxide (ITO) onto the organic semiconductor zinc phtalocyanine (ZnPc), which is important for inverted, transparent, and stacked organic light emitting diodes, is studied by in situ photoelectron spectroscopy (XPS and UPS). ITO was sputtered at room temperature and a low power density with a face to face arrangement of the target and substrate. With these deposition conditions, no chemical reaction and a low barrier height for charge injection at this interface are observed. The barrier height is comparable to those observed for the reverse deposition sequence, which also confirms the absence of sputter damage.