Annealed Indium Tin Oxide Research Articles

Solid‐State and Flexible Black Electrochromic Devices Enabled by Ni‐Cu Salts Based Organohydrogel Electrolytes

AbstractSolid‐state black electrochromic devices (ECDs) are promising for smart window applications, particularly when privacy protection and low leakage are required. Herein, a Ni–Cu salts/poly(vinyl alcohol) based organohydrogel electrolyte is developed with superior visible‐light transparency (83.8%), ionic conductivity (0.11 mS cm−1), and mechanical properties (tensile strength: 11.1 kPa, breaking strain: 242.6%). Due to the high viscosity of the organohydrogel electrolyte, a homogeneous Ni–Cu alloy film with a surface roughness of around 11.2 nm can be electrodeposited under −3 V for 5 min, and the resulting black color can be retained for over 350 min with a transmittance increase of only 5% at the voltage‐off state. The solid‐state rigid ECD exhibits an outstanding optical contrast between the transparent and colored states (visible light transmittance: 70.8% vs 0.085%), excellent cycling stability with over 90% retention of optical contrast after 2000 cycles. Finally, a flexible ECD is fabricated with the organohydrogel electrolyte and annealed indium tin oxide (ITO)‐coated polyethylene naphthalate (PEN) films as flexible and durable electrodes. It exhibits good mechanical flexibility with transmittance modulation degradation of 10% after 800 bending cycles and switching stability for 400 cycles with up to 43% optical contrast.

Influence of an Annealing Temperature in a Vacuum Atmosphere on the Physical Properties of Indium Tin Oxide Nanorod Films.

In the present study, indium tin oxide (ITO) nanorod films were produced by usage of ion-assisted electron-beam evaporation with a glancing angle deposition technique. The as-produced ITO nanorod films were annealed in the temperature range of 100-500 °C for two hours in a vacuum atmosphere. The as-produced ITO nanorod films exhibited (222) and (611) preferred orientations from the X-ray diffraction pattern. After vacuum annealing at 500 °C, the ITO nanorod films demonstrated many preferred orientations and the improvement of film crystallinity. The sheet resistance of the as-produced ITO nanorod films was 11.92 Ω/ and was found to be 13.63 Ω/ by annealing at 500 °C. The as-produced and annealed ITO nanorod films had a rod diameter of around 80 nm and transmittance in a visible zone of around 90%. The root mean square roughness of the as-produced ITO nanorod film's surface was 5.49 nm, which increased to 13.77 nm at an annealing temperature of 500 °C. The contact angle of the as-produced ITO nanorod films was 110.9° and increased to 116.5° after annealing at 500 °C.

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.

Flash lamp annealing of indium tin oxide thin-films deposited on polyimide backplanes

Xe-arc flashings of 0.4–1.0ms in pulse duration annealed indium tin oxide (ITO) thin-films deposited on flexible polymeric substrates at room temperature. As flexible substrates, highly transparent polyimide (PI) thin-films of 16μm in thickness were prepared on a carrier glass. Measuring optical characteristics of the ITO and the PI thin-films and using the Maxwell equations, we estimated complex refractive indices of ITO and PI materials. With the use of these optical properties, one-dimensional conduction/radiation heat transfer simulation was carried out to predict the temperature variations in the specimens, assuring that the temperature in the ITO thin-film during the flash lamp annealing (FLA) process exceeded its crystallization point. Experimental FLA process resulted in a significant enhancement of the electrical conductivities as well as in a slight increase of optical transmittances of the specimen and was compared with the conventional furnace annealing (CFA) process of 1h. Microscopic changes in the specimen during the annealing processes were compared using the X-ray diffraction pattern, atomic force microscope, and scanning electron microscope (SEM) measurements. Especially SEM images confirmed that sudden degradations in the electrical conductivities of ITO thin-films observed under higher power FLA or higher temperature CFA conditions were strongly related to the physical damages in the thin-films, which were incurred due to the thermal expansion mismatch between the ITO thin-film and the PI substrate at high temperatures.

Correlation between microstructure and electrical, optical properties of thermal annealed ITO thin films

Indium tin oxide (ITO) thin films with the thickness of 300 nm were deposited on quartz substrates via electron beam evaporation. Five samples were post-annealed in air atmosphere for 10 min at five selected temperature points from 200 to 600 °C, respectively. X-ray diffractometer, Hall measurement system and UV–Vis spectrophotometer were adopted to characterize the ITO thin films. Influence of thermal annealing in air atmosphere on microstructure was investigated. Furthermore, the correlation between microstructure and electrical, optical properties of ITO thin films was discussed in detail. All of the ITO thin films had a polycrystalline structure and a preferred orientation of (222), no matter annealed or not. The intensity ratio of I(222)/I(440) initially increased and then decreased, it reached the maximum of 7.37 after annealed at 400 °C for 10 min. The lattice expansion evidently reduced after annealed at 300 °C or even higher temperature. The variation of mean grain size was minor during thermal annealing process regardless of annealing temperature. The carrier concentration is predominant in electrical conductivity, and it is dependent on the activation of donors and the density of oxygen vacancies. Hall mobility is strongly dependent on the mean grain size, lattice distortion and defect density. The optical transmittance is influenced by the density of oxygen vacancies and the consistency of grain orientations.

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.

Effects of Post Annealing Temperatures on Sputtered Indium Tin Oxide Films for the Application to Resistive Touch Panel

Indium tin oxide (ITO) films were deposited on glass substrates by in-line DC sputtering and were annealed at different temperatures in the main chamber of sputter. The post-annealing effects on the optical and electrical properties of the ITO films were investigated and analyzed by various measurement systems. The results show that a higher annealing temperature makes an improvement on the electro-optical properties of the ITO films. The resistivity of the ITO films was reduced from 8.90×10−4Ω·cm to 2.91×10−4Ω·cm and the transmittance was increased from about 76.91% to 82.15% after post annealing at 300 °C in vacuum. The post annealed ITO glass was used in the fabrication of resistive touch panel and it was possible to obtain the better linearity characteristics than those from the touch panel fabricated with non-annealed ITO glass.

Temperature dependence of resistance and thermopower of thin indium tin oxide films

We have measured the resistance and thermopower of a series of RF sputtered and annealed indium tin oxide (ITO) thin films from 300 K down to liquid-helium temperatures. Thermal annealing was performed to modulate the levels of disorder (i.e., resistivity) of the samples. The measured resistances are well described by the Bloch–Grüneisen law between 150 and 300 K, suggesting that our thin films are metallic. At lower temperatures, a resistance rise with decreasing temperature was observed, which can be quantitatively ascribed to the two-dimensional electron–electron interaction and weak-localization effects. The thermopowers in all samples are negative and reveal fairly linear temperature dependence over the whole measurement temperature range, strongly indicating free-electron like conduction characteristics in ITO thin films. As a result, the carrier concentration in each film can be reliably determined. This work demonstrates that ITO films as thin as 15 nm thick can already possess high metallic conductivity.

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.

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.

UV–VIS and mid-IR ellipsometer characterization of layers used in OLED devices

We report on the analysis of layer materials commonly used for the fabrication of organic light-emitting diodes (OLEDs) by means of spectroscopic ellipsometry operating in the ultraviolet–visible (UV–VIS) and in the mid-infrared (mid-IR) range of the electromagnetic spectrum. On covering a wide spectral range, these non-destructive, non-contact techniques offer a huge potential in characterizing thin films in terms of layer thickness values, optical indices, absorption properties modified by incorporating optically active dopant molecules, and, finally, electrical layer properties. Individual absorption bands of single organic films can significantly affect the luminance and performance efficiency of OLEDs when building multi-layer stacks. Using mid-IR spectroscopic ellipsometry, the resistance of as-deposited and annealed indium–tin oxide (ITO) layers on glass is determined and compared with values obtained by four-point probe techniques.

Surface treatment effects of indium–tin oxide in organic light-emitting diodes

Abstract Effects of mechanically polished and annealed indium–tin oxide (ITO) substrate in tris-(8-hydroxyquinoline) aluminum (Alq3)-based light-emitting diodes were studied. It was found that roughness and oxygen content at ITO surface were reduced after the mechanical polishing. The organic light-emitting diodes (OLEDs) fabricated on the polished ITO surface showed 10 times better electroluminescence and current injection than the OLEDs based on as-received ITO surface, due to the increase of smooth contact area between the ITO surface and organic layer. The nucleation of TPD on ITO shows different feature according to the surface condition of ITO. As a result, the mechanical polishing is an effective treatment to enhance the performance of the OLEDs.

Radiation damage in air annealed indium tin oxide layers

The opto-electronic properties of pre-radiation annealed indium tin oxide (ITO) layers have been investigated. Having received a proton fluence of 10 17 ions cm −2, the annealed ITO layers were found to be highly resistant to proton damage. The as-deposit irradiated samples were found to be less resistant showing a rapid increase in resistivity with a corresponding degradation of the transmittance.

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.

Characterization of isochronally and isothermally annealed indium tin oxide thin films

Indium tin oxide (ITO) films of different compositions using respective alloys were prepared at relatively low substrate temperatures (130 °C) in an oxygen atmosphere of 10−4 Torr by reactive evaporation. The films were post annealed isochronally as well as isothermally and characterized by X-ray diffraction and scanning Auger microscopy. Electrical and optical properties were measured to optimize the preparation and annealing conditions. The properties of ITO films showed a strong dependence on annealing temperature and on the proportion of In and Sn. Maximum transmission was obtained for films wth 50 wt.% In and 50 wt.% Sn. The electrical resistivity p, carrier concentration ne and mobility μh were explained on the basis of oxygen vacancies and oxidation processes. Band gap widening with an increase in carrier density was observed and is explained on the basis of Burstein-Moss shift. Annealing just for 5 min at 500 °C was found to be enough to complete the oxidation process. The figure of merit was calculated and found to be satisfactory. From these studies it is concluded that these films can be used as transparent conductors.