Annealed Indium Tin Oxide Films Research Articles

Improved hole injection/extraction using PEDOT:PSS interlayer coated onto high temperature annealed ITO electrode for efficient device performances

We demonstrate the improved device performances by using the structure of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film coated onto the indium tin oxide (ITO) anodic electrode annealed at 400 °C under the normal ambient. The ITO thin films show the improved film quality with decreased dislocation density and lattice strain as annealing temperature increases. The spin-coated PEDOT:PSS film smoothens the wrinkle kind of surface morphology of the ITO film annealed at 400 °C. The annealed ITO (400 °C) with PEDOT:PSS interlayer improves the hole-current density in the hole-only devices (HODs) having the device structure of ITO/PEDOT:PSS/N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine as hole-transporting layer/Al. It enhances the efficiency of organic photovoltaic devices [ITO (annealed)/PEDOT:PSS/P3HT:PCBM (active layer)/LiF/Al] by three times higher (1.69 %) when compared to that (0.48 %) of pristine ITO based OPV device. These results show that the annealing of ITO film at the high temperature of 400 °C under the normal ambient improves the film quality and lowers the potential energy barrier at ITO/PEDOT:PSS interface for effective hole injection/extraction process, resulting in the enhanced device electrical performances. • Annealed ITO films improve film quality with decreased dislocation density and lattice strain. • PEDOT:PSS smoothens the wrinkle kind of surface morphology of ITO annealed at 400 °C. • 400 °C annealed ITO with PEDOT:PSS interlayer lowers the potential barrier and improves hole-current density in HODs. • It enhances the efficiency of OPVs by three times (1.69%) compared to that (0.48%) of pristine ITO based OPV. • 400 °C annealed ITO film lowers potential barrier at ITO/PEDOT:PSS interface for effective hole injection/extraction process.

IMPROVEMENT IN STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF ITO FILM THROUGH AlN AND HfO2BUFFER LAYERS

Indium Tin Oxide (ITO) films were deposited on glass substrate using radiofrequency (RF) magnetron sputtering technique. To improve the physical characteristics of the ITO film, AlN and HfO2buffer layers were deposited on glass prior to the film deposition. The ITO/glass, ITO/AlN/glass and ITO/HfO2/glass films were annealed using CO2laser and electrical oven heating methods. The crystallinity of the ITO film was improved due to the incorporation of AlN and HfO2buffer layers and also by the post-deposition annealing process. The optical transmittance of the ITO was also increased due to the presence of the buffer layers. Similarly, the annealed ITO films grown on buffer layers exhibited lower values of the sheet resistance as compared to the film deposited without buffer layers. The laser annealing technique was more found to be more effective in reducing the ITO sheet resistance.

Highly efficient ultraviolet high-harmonic generation from epsilon-near-zero indium tin oxide films

High-harmonic generation in the ultraviolet region is promising for wireless technology used for communications and sensing. However, small high-order nonlinear coefficients prevent us from obtaining high conversion efficiency and functional photonic devices. Here, we show highly efficient ultraviolet harmonic generation extending to the fifth order directly from an epsilon-near-zero indium tin oxide (ITO) film. The real part of the annealed ITO films was designed to reach zero around 1050 nm, matching with the central wavelength of an Yb-based fiber laser, and the internal driving electric field was extremely enhanced. A high energy conversion efficiency of 10 − 4 and 10 − 6 for 257.5 nm (fourth-order) and 206 nm (fifth-order) ultraviolet harmonic generation was obtained, which is at least 2 orders of magnitude higher than early reports. Our results demonstrate a new route for overcoming the inefficiency problem and open up the possibilities of compact solid-state high-harmonic generation sources at nanoscale.

Enhanced uniformity in electrical and optical properties of ITO thin films using a wide thermal annealing system

We investigated the effects of thermal treatment using a wide thermal annealing (w-TA) system on the structural, electrical, and optical properties of indium tin oxide (ITO) thin films deposited by radio-frequency magnetron sputtering at room temperature. The w-TA system was designed to enhance the uniformities of the electrical and optical properties of thin films in a large-scale 8G display substrate. The ITO films were annealed at 350 °C and 450 °C in a planar w-TA chamber. The X-ray diffraction analysis showed crystallization of ITO films along the 〈111〉 direction after the annealing process and an increase in their crystallite size with process temperature. The uniform characteristics of the electrical resistance and optical transmittance of ITO films are suitable for wide transparent electrodes, being the major advantage of the w-TA system. The sheet resistance (Rs) of the ITO thin films was lower, down to 18 Ω/□, and the variation of the Rs value was also narrowed down, which is measured by Rs at diverse points, after the w-TA process. The carrier concentration and mobility of the ITO films improved with an increase in annealing temperatures. The annealed ITO films exhibited both improved transmittance and better uniformity in the visible light region on a large 8G substrate. The band gap energy and carrier concentration of the ITO films increased after thermal annealing, as suggested by both the blue shift of the refractive index and the extinction coefficient values.

Low-Temperature Postfunctionalization of Highly Conductive Oxide Thin-Films toward Solution-Based Large-Scale Electronics.

Although transparent conducting oxides (TCOs) have played a key role in a wide range of solid-state electronics from conventional optoelectronics to emerging electronic systems, the processing temperature and conductivity of solution-processed materials seem to be far exceeding the thermal limitations of soft materials and insufficient for high-perfomance large-area systems, respectively. Here, we report a strategy to form highly conductive and scalable solution-processed oxide materials and their successful translation into large-area electronic applications, which is enabled by photoassisted postfunctionalization at low temperature. The low-temperature fabrication of indium-tin-oxide (ITO) thin films was achieved by using photoignited combustion synthesis combined with photoassisted reduction process under hydrogen atmosphere. It was noteworthy that the photochemically activated hydrogens on ITO surface could be triggered to facilitate highly crystalline oxygen deficient structure allowing significant increase of carrier concentration and mobility through film microstructure modifications. The low-temperature postfunctionalized ITO films demonstrated conductivity of >1607 S/cm and sheet resistance of <104 Ω/□ under the process temperature of less than 300 °C, which are comparable to those of vacuum-deposited and high-temperature annealed ITO films. Based on the photoassisted postfunctionalization route, all-solution-processed transparent metal-oxide thin-film-transistors and large-area integrated circuits with the ITO bus lines were demonstrated, showing field-effect mobilities of >6.5 cm2 V-1 s-1 with relatively good operational stability and oscillation frequency of more than 1 MHz in 7-stage ring oscillators, respectively.

Effect of annealing time on the structural, optical and electrical characteristics of DC sputtered ITO thin films

Using an Indium tin oxide (ITO) ceramic target (In2O3:SnO2, 90:10 wt%), ITO thin films were deposited by conventional direct current magnetron sputtering technique onto glass substrates at room temperature. The obtained ITO films were annealed at 400 °C for different annealing times (1, 2, 5, 7, and 9 h). The effect of annealing time on their structural, optical and electrical properties was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microcopy (AFM), ultra violet–visible (UV–Vis) spectrometer, and temperature dependence Hall measurements. XRD data of obtained ITO films reveal that the films were polycrystalline with cubic structure and exhibit (222), (400) and (440) crystallographic planes of In2O3. AFM and Scanning Electron Microscopy SEM have been used to probe the surface roughness and the morphology of the films. The refractive index (n), thickness and porosity (%) of the films were evaluated from transmittance spectra obtained in the range 350–700 nm by UV–Vis. The optical band gap of ITO film was found to be varying from 3.35 to 3.47 eV with the annealing time. The annealing time dependence of resistivity, carrier concentration, carrier mobility, sheet resistance, and figure of merit values of the films at room temperature were discussed. The carrier concentration of the films increased from 1.21 × 1020 to 1.90 × 1020 cm−3, the Hall mobility increased from 11.38 to 18 cm2 V−1 s−1 and electrical resistivity decreased from 3.97 × 10−3 to 2.13 × 10−3 Ω cm with the increase of annealing time from 1 to 9 h. Additionally, the temperature dependence of the carrier concentration, and carrier mobility for the as-deposited and 400 °C annealed ITO films for 2 and 9 h were analysed in the temperature range of 80–350 K.

The effect of post-annealing on Indium Tin Oxide thin films by magnetron sputtering method

Abstract We report effects of post-annealing on Indium Tin Oxide (ITO) thin films by their physical, electrical, optical, and electronic properties. Carrier concentrations increase up to annealing temperatures of 400 °C, and then decrease at higher annealing temperatures. Burstein–Moss effect occurs as a function of annealing temperature with the highest optical bandgap of 4.17 eV achieved at 400 °C. X-ray photoelectron spectroscopy revealed a ∼0.3 eV shift in the Fermi level of the annealed ITO films at 400 °C, and the shift was reduced for temperatures higher than 400 °C. In addition, the results of curve-fitting for the core levels showed a change of ratios of SnO2 and oxygen in the oxygen deficient regions after annealing. This is correlated to the change of carrier concentration and optical bandgap in the ultraviolet and near-infrared regions at different annealing temperatures.

Effects of annealing temperature on mechanical durability of indium-tin oxide film on polyethylene terephthalate substrate

Effects of the annealing temperature on mechanical durability of indium-tin oxide (ITO) thin films deposited on polyethylene terephthalate (PET) substrates were investigated. The ITO films were annealed at the range from 150°C to 195°C after the DC sputtering deposition for the production of polycrystalline ITO layers on the substrates. The onset strains of cracking in the annealed ITO films were evaluated by the uniaxial stretching tests with electrical resistance measurements during film stretching. The results indicate that the onset strain of cracking in the ITO film is clearly increased by increasing the annealing temperature. The in-situ measurements of the inter-planer spacing of the (222) plane in the crystalline ITO films during film stretching by using synchrotron radiation strongly suggest that the large compressive stress in the ITO film increases the onset strain of cracking in the film. X-ray stress analyses of the annealed ITO films and thermal mechanical analyses of the PET substrates also clarifies that the residual compressive stress in the ITO film is enhanced with increasing the annealing temperature due to the considerably larger shrinkage of the PET substrate.

Structural, Optical and Morphological Studies on Nanostructure ITO Thin Films

Indium tin oxide (ITO) thin films exhibiting good transmittance and conductivity suitable for solar cell applications have been prepared on Si(100) and fused silica substrates by optimizing the dc sputtering parameters such as power density and Ar partial pressure. Structural analysis of the as-deposited and annealed ITO films indicated that the as-deposited films are predominantly amorphous, whereas the films annealed at 200–400 °C are found to be of polycrystalline nature exhibiting dominant peaks corresponding to the (222) and (400) planes. The optical transmittance and band gap values of the films are observed to exhibit a change on annealing. From the ellipsometry studies on ITO/Si annealed at 300°C, it is found that graded layer consist of the mixing of two ITO materials with slightly different optical constants and the grading is almost linear. The resistivity of the ITO films is found to decrease with annealing temperature, correlating with the improvement in the crystal quality, and values in the range of 2-3 x10-4 Ω-cm are observed for the films annealed at 300°C. Surface topography study of the films has been performed using atomic force microscope(AFM) and the results are discussed.

Fiber laser annealing of indium-tin-oxide nanoparticles for large area transparent conductive layers and optical film characterization

Indium tin oxide (ITO) coatings are widely used as transparent electrodes for optoelectronic devices. The most common preparation methods are sputtering, evaporation, and wet chemical deposition. ITO coatings can also be manufactured by solution deposition of ITO nanoparticles followed by furnace thermal annealing with the major motivation to reduce equipment investment. However, conventional furnace annealing is energy intensive, slow, and limited by the peak processing temperature. To overcome these constraints, we suggest using a laser beam for ITO nanoparticle annealing over a large area. It is shown in the present study that a low cost, high power, and high efficiency laser can yield large area functional ITO films in a process that carries substantial promise for potential industrial implementation. Furthermore, laser annealing generates higher electrical conductivity than conventional, thermally annealed nanoparticle films. The optical and electrical properties of the annealed ITO films can also be altered by adjusting laser parameters and environmental gases.

热退火提升氧化铟锡之光穿透率以及导电度

The effect of annealing condition on sputtered indium tin oxide (ITO) films on quartz with the thickness of 200 nm is characterized to show enhanced optical transparency and optimized electrical contact resistivity. The as-deposited grown ITO film exhibits only 65% and 80% transmittance at 532 and 632.8 nm, respectively. After annealing at 475 oC for 15 min, the ITO film is refined to show improved transmittance at shorter wavelength region. The transmittances of 88.1% at 532 nm and 90.4% at 632.8 nm can be obtained. The 325-nm transmittance of the post-annealed ITO film is greatly increased from 12.7% to 41.9%. Optimized electrical property can be obtained when annealing below 450 oC, leading to a minimum sheet resistance of 26 \Omega/square. Such an ITO film with enhanced ultraviolet (UV) transmittance has become an alternative candidate for applications in current UV photonic devices. The morphology and conductance of the as-deposited and annealed ITO films are determined by using an atomic force microscopy (AFM), showing a great change on the uniformity distribution with finite improvement on the surface conductance of the ITO film after annealing.

Influence of Structural and Electrical Properties of ITO Films on Electrochromic Properties of WO&lt;sub&gt;3&lt;/sub&gt; Films

Indium tin oxide (ITO) films had been deposited on glass substrate without substrate heating and then tungsten oxide (WO3) films were deposited on ITO films by DC magnetron sputtering. In this work, we present the annealing ambient effect of ITO substrate on electrochromic properties of WO3 films. The ITO films were annealing in air and in vacuum at 350°C before coating with WO3 films. The structural, optical, and electrical properties of ITO films for as-deposited, annealing in air and in vacuum were investigated by X-ray diffraction, UV-VIS-NIR spectroscope and four point probe. The ITO films had a better crystallinity and lager grain size after annealing in air and in vacuum. The resistivity of ITO films increase with annealing in air, but decrease with annealing in vacuum. The WO3 films show difference surface morphology with higher grain size and surface roughness when coating on annealed ITO films in both cases. The electrochemical properties of film systems were characterized by cyclic voltammetry. The film systems of ITO plus WO3 showed that the charge capacity of ITO substrate annealing in vacuum was higher than the as-deposited ITO substrate and the ITO substrate annealing in air, respectively. This result corresponded to electrical conductivity of each ITO substrate.

Thermal stability of indium tin oxide thin films co-sputtered with zinc oxide

The thermal stability of indium tin oxide (ITO) films and ITO co-sputtered with zinc oxide (ZnO) films at different zinc atomic ratios in various atmospheres are investigated. The resistivity of the annealed ITO films decreased with increased annealing temperatures. The improved electrical properties were attributed mainly to the increase in carrier concentration originating from the significant formation of oxygen vacancies in the ITO films. In contrast, due to the lower oxidation potential of zinc ions, the resistivity of the annealed co-sputtered films showed no significant reduction and an increase with annealing temperatures. The film decomposition due to the high degree outdiffusion of oxygen atoms and aggregation of In atoms observed from the metal-like In phase in the diffraction patterns was responsible for the drastic thermal degradation in the electrical and optical properties of the samples annealed at elevated temperatures in reducing gas atmosphere. In contrast, the superior thermal stability of the co-sputtered films, at an atomic ratio of 60% annealed in reducing gas atmospheres, was ascribed to the stable Zn 3In 2O 6 crystalline structure that appeared in the diffraction pattern. The absorption edge observed from the optical transmittance of these annealed films also showed evidence of carrier concentration evolution in various annealing atmospheres. The lower oxidation potential of the zinc atoms introduced into the ITO films was concluded to be efficient in compensating for the formation of oxygen vacancies resulting in the alleviated decomposition behavior during thermal annealing.

Gallium nitride photoconductive ultraviolet sensor with a sputtered transparent indium–tin–oxide ohmic contact

A gallium nitride (GaN) photoconductive ultraviolet sensor with a sputtered transparent indium–tin–oxide (ITO) contact is presented, in which a maximum photo-responsivity of 327 A/W at a bias of 5 V and a wavelength of 366 nm is achieved and attributed to good ohmic contact between ITO and n-type GaN layer. It is shown that as-deposited and annealed ITO films deposited onto n-type GaN using a radio frequency sputtering produce linear current–voltage curves that are believed to be the origin of the high photo-responsivity. In addition, annealing is shown to improve transmittance through the ITO films.

PREPARATION AND CHARACTERIZATION OF ITO THIN FILMS ON GLASS BY A SOL–GEL PROCESS USING METAL SALTS

Indium-tin-oxide (ITO) thin film is one of the indispensable materials for advanced optoelectric technologies. In this work, uniform and transparent ITO films were deposited onto glass substrates using a sol–gel method. The initial sols were prepared from anhydrous ethanol solutions of indium nitrate ( In ( NO 3)3·1 H 2 O ) and tin chloride ( SnCl 4), with different In:Sn ratios. The sols were dip-coated on the substrates and were subjected to annealing at different temperatures. Depending on compositions, the electrical resistivity of ITO coating varied from 1.4×103Ω/□ to 3.5×103Ω/□, and the minimum value for the electric resistivity was observed for the films containing 8% Sn by weight. Increasing heat treatment-temperatures from 400 to 600°C led to increase in conductivity by one order of magnitude. The optical transmittance of 550°C-annealed ITO films was more than 90% in the visible region. The morphology of the ITO films was examined by scanning tunneling microscopy (STM) and scanning electron microscopy (SEM). The rms-roughness of 350 nm thick ITO film was 1.5 nm. Increasing film thickness resulted in decrease in both, surface roughness and electrical resistivity. The correlations among the film properties and the film preparation conditions are discussed in detail.

Piezoresistive Properties of ITO Strain Sensors Prepared with Controlled Nanoporosity

A ceramic strain gage based on reactively sputtered indium-tinoxide (ITO) thin films is being developed to monitor the structural integrity of components employed in aerospace propulsion systems operating at temperatures in excess of 1500°C. The high-temperature stability and piezoresistive properties depend to a large extent on the thickness of the active ITO strain elements comprising these ceramic strain gages. Scanning electron microscopy of the thick ITO sensors revealed a partially sintered microstructure consisting of a contiguous network of submicrometer ITO particles with well-defined necks and isolated nanoporosity. It appeared that densification of the ITO particles was retarded during high-temperature exposure with nitrogen playing a key role in stabilizing the nanoporosity. Based on these preliminary results, ITO strain sensors were also prepared by reactive sputtering in various nitrogen/oxygen/argon partial pressures to incorporate more nitrogen into the films. Under these conditions, sintering and densification of the ITO particles containing these nitrogen-rich grain boundaries was retarded and a contiguous network of nanosized ITO particles was established. The influence of nitrogen in the sputtered and annealed ITO films on the microstructure and the high-temperature piezoresistive properties was investigated, and the results are presented in this paper. © 2004 The Electrochemical Society. All rights reserved.

Indium tin oxide films with low resistivity and low internal stress

Indium tin oxide (ITO) films prepared by dc magnetron sputtering were annealed in air, vacuum, and oxygen gas atmospheres. The electrical properties and internal stresses of these annealed ITO films were systematically investigated. It was found that, among the above postannealing treatments, oxygen gas annealing significantly reduced both the resistivity and the internal stress in ITO films at fairly low temperatures of 100–150 °C. Resistivities and internal stresses as low as 7×10−4 Ω cm and 38 MPa, respectively, were obtained by annealing in oxygen gas atmosphere at 100 °C. It was also revealed that the (111) crystal orientation becomes dominant and that whole grains grow dramatically as a result of postoxygen annealing, even at 100 °C.

Study of annealed indium tin oxide films prepared by rf reactive magnetron sputtering

Tin doped indium oxide (ITO) films were deposited on glass substrates by rf reactive magnetron sputtering using a metallic alloy target (In-Sn, 90-10). The post-deposition annealing has been done for ITO films in air and the effect of annealing temperature on the electrical, optical and structural properties of ITO films was studied. It has been found that the increase of the annealing temperature will improve the film electrical properties. The resistivity of as deposited film is about 1.3 × 10 −1 gW ∗ cm and decreases down to 6.9 × 10 −3 Ω ∗ cm as the annealing temperature is increased up to 500 °C. In addition, the annealing will also increase the film surface roughness which can improve the efficiency of amorphous silicon solar cells by increasing the amount of light trapping.

Study of annealed Indium Tin Oxide Films Prepared by RF Reactive Magnetron Sputtering

AbstractTin doped indium oxide (ITO) films were deposited on glass substrates by rf reactive magnetron sputtering using a metallic alloy target (In-Sn, 90-10). the post-deposition annealing has been done for ITO films in air and the effect of annealing temperature on the electrical, optical and structural properties of ITO films was studied. It has been found that the increase of the annealing temperature will improve the film electrical properties. the resistivity of as-deposited film is about 1.3 х 10-1 Ω*cm and decreases down to 6.9 х 10-3Ω*cm as the annealing temperature is increased up to 500 °C. IN addition, the annealing will also increase the film surface roughness which can improve the efficiency of amorphous silicon solar cells by increasing the amount of light trapping.