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.     

Work function of sol-gel indium tin oxide (ITO) films on glass

Indium tin oxide (ITO) films (physical thickness, 250-560 ± 25 nm) were deposited on soda lime silica (SLS) glass and silica layer coated (∼200 nm physical thickness) SLS glass substrates by sol-gel technique using alcohol based precursors containing different In:Sn atomic percentages, namely, 90:10, 70:30, 50:50, 30:70. Cubic phase of In₂O₃ was observed up to 50 at.% Sn while cassiterite SnO₂ phase was observed for 70 at.% Sn. Work function of the films was evaluated from inelastic secondary electron cutoff of ultraviolet photoelectron spectroscopy (UPS) energy distribution curve (EDC) obtained under two experimental conditions (i) as-introduced (ii) after the cleaning of the surface by sputtering. Elemental distribution and the presence of oxygen containing contaminant and carbon contaminant of the samples were done by XPS analysis under same conditions. The work function changed little due to the presence of surface contaminants. It was in the range, 3.9-4.2 eV (±0.1 eV).     

Laser-driven high-resolution patterning of indium tin oxide thin film for electronic device

We here introduce a laser-driven process to pattern transparent thin films on transparent substrates. This method utilizes a pre-patterned metal film as the dynamic release layer and the transparent thin film is selectively removed by a thermo-elastic force laser-induced in the underlying metal layer. High-fidelity indium tin oxide (ITO) thin film patterns were fabricated on plastic and glass substrates using a pulsed Nd:YAG laser. Tens of square centimeters could be patterned with several pulse shots. We fabricated a pentacene thin film transistor with ITO source and drain electrodes and observed a very low off-current level. This tells that the channel area between ITO electrodes was completely etched out by this laser-driven process. Combined with the absence of photoresist and chemical etching steps, this method provides a simple high-resolution route to pattern transparent thin films over large areas at low temperatures.     

Part 2: Ultra-short pulse laser patterning of very thin indium tin oxide on glass substrates

We investigate selective patterning of ultra-thin 20 nm Indium Tin Oxide (ITO) thin films on glass substrates, using 343, 515, and 1030 nm femtosecond (fs), and 1030 nm picoseconds (ps) laser pulses. An ablative removal mechanism is observed for all wavelengths at both femtosecond and picoseconds time-scales. The absorbed threshold fluence values were determined to be 12.5 mJ cm⁻² at 343 nm, 9.68 mJ cm⁻² at 515 nm, and 7.50 mJ cm⁻² at 1030 nm for femtosecond and 9.14 mJ cm⁻² at 1030 nm for picosecond laser exposure. Surface analysis of ablated craters using atomic force microscopy confirms that the selective removal of the film from the glass substrate is dependent on the applied fluence. Film removal is shown to be primarily through ultrafast lattice deformation generated by an electron blast force. The laser absorption and heating process was simulated using a two temperature model (TTM). The predicted surface temperatures confirm that film removal below 1 J cm⁻² to be predominately by a non-thermal mechanism.     

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.     

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.     

Substrate-assisted laser patterning of indium tin oxide thin films

Maskless laser patterning of indium tin oxide (ITO) thin films was studied by the use of a diode-pumped Q-switched Nd:YLF laser. The ITO films were sputter-deposited either on lime glass, the standard substrate material for flat panel display applications, or fused quartz so that the efficiency of laser patterning as a function of substrate absorption could be studied. The laser wavelength was varied among infrared (5=1047 nm), visible (5=523 nm), and ultraviolet (5=349 nm and 5=262 nm). It is observed that strong light absorption by the substrate is a crucial requirement for a residue-free patterning of the ITO film. Observations and numerical calculations of the laser-induced surface temperature indicate that material removal occurs via thermal vaporization and that other mechanisms such as photochemical decomposition or spallation can be neglected.     

反应离子镀制备ITO膜

采用反应离子镀新工艺成功地在K9玻璃上制备了ITO(Indium Tin Oxide)透明导电膜,所制备的ITO膜在550～600nm波长范围内,典型的峰值透过率为89%,面电阻为34Ω/□。     

Laser scribing of indium tin oxide (ITO) thin films deposited on various substrates for touch panels

In this study, a Nd:YAG laser with wavelength of 1064 nm is used to scribe the indium tin oxide (ITO) thin films coated on three types of substrate materials, i.e. soda-lime glass, polycarbonate (PC), and cyclic-olefin-copolymer (COC) materials with thickness of 20 nm, 30 nm, and 20 nm, respectively. The effect of exposure time adjusted from 10 μs to 100 μs on the ablated mark width, depth, and electrical properties of the scribed film was investigated. The maximum laser power of 2.2 W was used to scribe these thin films. In addition, the surface morphology, surface reaction, surface roughness, optical properties, and electrical conductivity properties were measured by a scanning electron microscope, a three-dimensional confocal laser scanning microscope, an atomic force microscope, and a four-point probe. The measured results of surface morphology show that the residual ITO layer was produced on the scribed path with the laser exposure time at 10 μs and 20 μs. The better edge qualities of the scribed lines can be obtained when the exposure time extends from 30 μs to 60 μs. When the laser exposure time is longer than 60 μs, the partially burned areas of the scribed thin films on PC and COC substrates are observed. Moreover, the isolated line width and resistivity values increase when the laser exposure time increases.     

Vanadium oxide thin films deposited on indium tin oxide glass by radio—frequency magnetron sputtering

Highly oriented VO₂(B), VO₂(B) + V₆O₁₃ films were grown on indium tin oxide glass by radio-frequency magnetron sputtering. Single phase V₆O₁₃ films were obtained from VO₂(B) +V₆O₁₃ films by annealing at 480℃ in vacuum. The vanadium oxide films were characterized by x-ray diffraction and x-ray photoelectron spectra (XPS). It was found that the formation of vanadium oxide films was affected by substrate temperature and annealing time, because high substrate temperature and annealing were favourable to further oxidation. Therefore, the formation of high valance vanadium oxide films was realized. The V₆O₁₃ crystalline sizes become smaller with the increase of annealing time. XPS analysis revealed that the energy position for all the samples was almost constant, but the broadening of the V_2p3/2 line of the annealed sample was due to the smaller crystal size of V₆O₁₃.     

A study of stitch line formation during high speed laser patterning of thin film indium tin oxide transparent electrodes

High speed laser patterning of indium tin oxide thin films on glass is part of the production method used to produce transparent conductive electrodes for plasma display panels. Such a design consists of rows of repeating electrode structures which cover the active area of the display. Whilst the patterning process for such electrode structures exceeds the industrial acceptance criteria there are certain features that are yet to be fully understood. The visible line that occurs in-between two adjacent laser processed areas, commonly known as a stitch line, is one such feature. Previously published research claimed that the stitch line was caused by incomplete removal of the thin film however experimental results presented within this paper demonstrate that this cannot be the case and show that the stitch line is formed by redeposition of the plume of ablated material within the area of overlap with the previous pulse, and that heating of the sample by the second pulse plays a key role in stitch line formation.     

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.     

F2-laser ablation patterning of dielectric layers

Spatially defined patterning of multi-layer dielectric optical systems by laser-induced ablation is demonstrated. A 49-layer high-reflectivity mirror for 193-nm light was irradiated with F₂-laser light through the CaF₂-substrate to cleanly remove the whole dielectric stack by rear-sided ablation. The 157-nm light is absorbed efficiently by dielectric layers such as SiO₂ and Al₂O₃ that are typically used for ultraviolet (UV) transmission at 193-nm and longer wavelengths. Thus it is possible to ablate highly reflective UV-laser mirrors (HR 193 nm) and to create dielectric masks that withstand high power levels at 193 nm. A single 157-nm pulse with a fluence of less than 500 mJ/cm² is sufficient to cleanly ablate the whole layer stack with sharp edges and without debris deposition. Received: 31 October 2000 / Accepted: 14 November 2000 / Published online: 10 January 2001     

Development of conductive transparent indium tin oxide (ITO) thin films deposited by direct current (DC) magnetron sputtering for photon-STM applications

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10^-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10^-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10^-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated. Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001     

The insert of zinc oxide thin film in indium tin oxide anode for organic electroluminescence devices

Zinc oxide films were prepared by rf magnetron sputtering on glass substrates with designed ZnO target using high-purity of zinc oxide (99.99%) powder. Systematic study on dependence of target-to-substrate distance (D_ts) on structural, electrical and optical properties of the as-grown ZnO films was mainly investigated in this work. XRD showed that highly preferred ZnO crystal in the [0 0 1] direction was grown in parallel to the substrate, while the D_ts did not effect to the peak position of XRD. With decreasing D_ts, the growth rate is increased while the electrical resistivity as well as crystal size in the ZnO films was decreased. The XPS data showed that the O/Zn ratio in ZnO films was increased with increasing D_ts in the films. The as-grown ZnO films have an average transmittance of above 85% at the visible region. The optical band gap of the as-grown ZnO films was changed from 3.18 to 3.36 eV with D_ts. With decreasing D_ts, the electrical resistivity was decreased, while the growth rate was increased.A bilayer is used as an anode electrode for organic electroluminescent devices. The bilayer consists of an ultrathin ZnO layer adjacent to a hole-transporting layer and an Indium tin oxide (ITO) outerlayer. We tried to bring low the barrier between the devices as deposited ZnO films on ITO substrates. We fabricated the organic EL structure consisted of Al as a cathode, Al₂O₃ as an electro transport layer, Alq₃ as a luminously layer, TPD as a hole transport layer and ZnO (1 nm)/ITO (150 nm) as an anode. The result of this experiment was not good compared with the case of using ITO, nevertheless, at this structure we obtained the lowest turn-on voltage as the value of 19 V and the good brightness (6200 cd/m²) of the emission light from the devices. Then the quantum efficiency was to be 1.0%.     

铟锡氧化物薄膜表面等离子体损耗降低的研究

本文采用直流磁控溅射方法在普通浮法玻璃基底上制备了立方多晶铁锰矿结构的铟锡氧化物(indium tin oxide, ITO)薄膜,并对其进行了结晶性、表面粗糙度、紫外-可见吸收光谱、折射率、介电常数及霍尔效应的测试.研究了溅射时基底温度的改变对于ITO薄膜的光电、表面等离子体性质的影响.随着基底温度由100?C升高至500?C,其光学带隙(3.64—3.97eV)展宽,减少了电子带间跃迁的概率,有效降低了ITO薄膜的光学损耗.与此同时,对应ITO薄膜的载流子浓度(4.1×10~(20)-—2.48×10~(21)cm~(-3))与迁移率(24.6—32.2 cm~2·V~(-1)·s~(-1))得到提高,电学损耗明显降低.     

Incubation effect and its influence on laser patterning of ITO thin film

Results are presented on the surface damage thresholds of ITO thin films induced by single- and multi-pulse laser irradiation at a pulse duration of 10 ps and a wavelength of 1064 nm. For multi-pulse ablation the incubation effect results in a reduction of the damage threshold, especially apparent at low pulse numbers and very small film thicknesses. The incubation effect attributes to the accumulation of defect sites and/or the storage of thermal stress-strain energy induced by the incident laser pulses. An incubation coefficient of S=0.82 has been obtained which is independent on the film thickness in the range of 10–100 nm. In practical applications, the incubation effect determines the laser patterning structure of ITO films while increasing the pulse overlapping rate. The width of the patterned line can be predicted by the proposed model involving the laser fluence, the overlapping rate and the incubation coefficient.     

Selective patterning and scribing of Ti thin film on glass substrate by 532 nm picosecond laser

In this paper, the feasibility of Ti film coated on glass substrate scribed via a 532 nm picosecond laser is investigated. Laser irradiations from the film side and from the transparent substrate side are performed for comparison. Optical microscopy, SEM, surface stylus and contact resistance measurement reveal that the Ti film can be completely removed with no damage to the glass substrate, using optimized process parameters. The complete removal threshold for the film for front-side scribing is found at 120 mJ/cm², while the minimum laser fluence for complete scribing is 70 mJ/cm² in the case of back-side scribing. The lines scribed from the front side exhibit obvious thermal effects such as heat affected zones, burr and micro cracks. Back-side scribing exhibits non-thermal behavior, which also can increase the process speed for the scribing of a Ti film on glass to 1000 mm/s. This makes the back-side laser scribing of Ti film a promising technique.     

Effect of substrate temperature on properties of multilayer thin film based on ZnO and Mo-doped indium oxide

Zinc oxide/molybdenum-doped indium oxide/zinc oxide (ZnO/IMO/ZnO) multilayer thin films are grown using pulsed laser deposition technique. The effect of substrate temperature on structural, optical, and electrical properties of multilayer films is studied. It is observed that films grown at high substrate temperature are oriented along (0 0 2) and (2 2 2) direction for ZnO and IMO respectively. The crystallinity of these films increases with increase in substrate temperature. It is also seen that conductivity, carrier concentration, and mobility increase with increase in temperature. The multilayer film grown at 500 °C has low resistivity (7.67 × 10⁻⁵ Ω cm), high carrier concentration (3.90 × 10²⁰ cm⁻³), and high mobility (209 cm²/Vs).     

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%.