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.     

Laser direct patterning induced the tunable optical properties of indium tin oxide micro-hole arrays films

Here we introduce a facile method to fabricate patterned indium tin oxide (ITO) thin films via selective laser ablation at ambient conditions. By scanning the ITO thin films with focused Nd: YAG pulsed laser, the ITO thin films were selective ablated and patterned without using any conventional chemical etching or photolithography steps. Then we investigated the effects of scanning rate for the structure, morphology and optical properties of patterned ITO thin film. These results indicate that the epsilon-near-zero (ENZ) wavelength of ITO thin films can be tuned from 1100 nm to 1340 nm by adjusting the period of the micro-hole array in microstructure. The nonlinear absorption response of patterned ITO films was about 2.85 time than of the as-deposited ITO thin film. Additionally, the results of the Finite-Difference Time-Domain (FDTD) simulation are in good agreement with those of the experiments.     

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.     

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.     

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%.     

In2O3 透明薄膜晶体管的制备及其电学性能的研究

采用磁控溅射方法在玻璃衬底上生长了In₂O₃晶体薄膜.该薄膜具有(111)晶面择优取向,晶粒尺寸达到33 nm.利用光刻工艺制作了以In₂O₃晶体薄膜为沟道层的底栅式薄膜晶体管.In₂O₃薄膜晶体管具有良好的栅压调制特性,场效应迁移率达到6.3 cm²/(V·s),开关电流比为3×10³,阈值电压为-0.9 V.结果表明,In相似文献   

Optical characteristics of light-emitting diodes with high transparent conductive film at low temperatures

In this paper, we report the synthesis and transmittance of a titanium–indium–tin oxide (TITO) film, fabricated through a low-temperature process. The TITO film was fabricated by incorporating a 2-nm-thick titanium barrier at the bottom of an ITO film. The transmittance characteristics of the TITO film were examined for light-emitting diodes (LEDs) of various wavelengths at different post-annealing temperatures. A saturated high transmittance was observed at a temperature of 550 °C, which is relatively low when compared to that in the case of a conventional ITO film. Photoluminescence studies demonstrated that a 450-nm-thick TITO film, fabricated at 550 °C, was highly effective in improving the performance of the LED, when compared to conventional ITO films. The X-ray diffraction peaks, scanning electron microscopy images, and transmittance electron microscopy images confirmed that titanium atoms could improve the crystallization of ITO. It was found that non-crystallization in ITO was effectively activated by the titanium barrier. Furthermore, the optical bandgap (3.77 eV for the conventional ITO film) was improved to 3.92 eV in the TITO film. An infrared LED fabricated with a TITO film displayed 70% higher light output power than that with a conventional ITO film. These results suggest that using a titanium barrier is essential to effectively improve inactive nucleation sites in ITO films grown at low temperatures.     

非晶铟锌氧化物薄膜晶体管的低频噪声特性与分析

本文针对底栅结构非晶铟锌氧化物薄膜晶体管的低频噪声特性开展实验与理论研究.由实验结果可知:受铟锌氧化物与二氧化硅界面处缺陷态俘获与释放载流子效应的影响,器件沟道电流噪声功率谱密度随频率的变化遵循1/fγ(γ≈0.75)的变化规律;此外,器件沟道电流归一化噪声功率谱密度随沟道长度与沟道宽度的增加而减小,证明器件低频噪声来源于沟道的闪烁噪声,可忽略源漏结接触及寄生电阻对器件低频噪声的影响.最后,基于载流子数涨落及迁移率涨落模型,提取γ因子与平均Hooge因子,为评价材料及器件特性奠定基础.     

激光辐照对热退火金属/掺氟二氧化锡透明导电薄膜光电性能的影响

采用532 nm纳秒脉冲激光对热退火的铝(Al)/掺氟二氧化锡(FTO)、铜(Cu)/FTO和银(Ag)/FTO三种双层复合薄膜表面分别进行处理, 结果显示薄膜样品的光电性能都得到提高.其中, 热退火Ag/FTO薄膜的平均透光率(400–800 nm)增幅最大, 从72.6%提高到80.5%, 主要是由于其表面产生了具有减反增透作用的光栅结构.激光辐照后热退火Ag/FTO薄膜的导电性也略有提高, 其方块电阻从5.6 Ω/sq下降到5.3 Ω/sq, 原因主要是激光辐照的热效应造成的退火作用使薄膜的晶粒尺寸增大, 减少了晶界散射而使载流子迁移率提高.计算结果显示, 激光辐照后热退火Ag/FTO薄膜的品质因子从0.73×10^-2Ω^-1增大为2.16×10^-2Ω^-1, 表明其综合光电性能得到显著提高.激光辐照可同步实现薄膜表面光栅结构的制备和附加退火作用, 这为金属层复合透明导电薄膜光电性能的综合优化提供了新的思路.     

Electrochromic properties of WO3 thin film onto gold nanoparticles modified indium tin oxide electrodes

Gold nanoparticles (GNPs) thin films, electrochemically deposited from hydrogen tetrachloroaurate onto transparent indium tin oxide (ITO) thin film coated glass, have different color prepared by variation of the deposition condition. The color of GNP film can vary from pale red to blue due to different particle size and their interaction. The characteristic of GNPs modified ITO electrodes was studied by UV-vis spectroscopy, scanning electron microscope (SEM) images and cyclic voltammetry. WO₃ thin films were fabricated by sol-gel method onto the surface of GNPs modified electrode to form the WO₃/GNPs composite films. The electrochromic properties of WO₃/GNPs composite modified ITO electrode were investigated by UV-vis spectroscopy and cyclic voltammetry. It was found that the electrochromic performance of WO₃/GNPs composite films was improved in comparison with a single component system of WO₃.     

Modeling of In2O3-10 wt% ZnO thin film properties for transparent conductive oxide using neural networks

Effects of deposition process parameters on the deposition rate and the electrical properties of In₂O₃–10 wt% ZnO (IZO) thin films were modeled and analyzed by using the error back-propagation neural networks (BPNN). Output models were represented by response surface plots and the fitness of models was estimated by calculating the root mean square error (RMSE). The deposition rate of IZO thin films is affected by the RF power and the substrate temperature. The electrical properties of the IZO thin films are mainly controlled by O₂ ratio and the substrate temperature. The predicted output characteristics by BPNN can sufficiently explain the mechanism of IZO deposition process. Thus, neural network models can provide the reliable explanation of IZO film deposition.     

Synthesis of P-type transparent conducting silver:indium oxide (AIO) thin films by reactive electron beam evaporation technique

Present paper reports the synthesis, electrical and optical properties of p-type conducting and transparent silver indium oxide (AIO) thin films prepared on glass substrates by reactive electron beam evaporation technique at three substrate temperatures (50, 200 and 250 °C) and at five evaporation rates (0.05 to 16.0 nm/s). The source material is pure powders of Ag₂O:In₂O₃=50:50 mol%. The AIO films are amorphous. The films, though not corresponding to Delafossite crystal structure, exhibit p-type conductivity, when prepared at an evaporation rate of 0.05 nm/s at all the three substrate temperatures. With increasing filament current, it is observed that (i) the electrical resistivity decreases and (ii) the refractive index of the films (at 632.8 nm, and is in the range: 1.219-1.211) decreases. The work function (effective Fermi level) has been measured on these samples by Kelvin Probe method. The results are explained on the basis of partial ionic charge and localization of covalent bonds in the AIO thin films.     

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.     

铜-钼源漏电极对非晶氧化铟镓锌薄膜晶体管性能的改善

在铜(Cu)和非晶铟镓锌氧化物(a-IGZO)之间插入30 nm厚的钼(Mo)接触层, 制备了具有Cu-Mo源漏电极的a-IGZO薄膜晶体管(TFT). Mo接触层不仅能够抑制Cu与a-IGZO有源层之间的扩散, 而且提高了Cu电极与玻璃基底以及栅极绝缘层的结合强度. 制备的Cu-Mo结构TFT与纯Cu 结构TFT相比, 具有较高的迁移率(～9.26 cm²·V^-1·s^-1)、更短的电流传输长度(～0.2 μm)、更低的接触电阻(～1072 Ω)和有效接触电阻率(～1×10^-4Ω·cm²), 能够满足TFT 阵列高导互联的要求.     

A possible origin of room temperature ferromagnetism in Indium-Tin oxide thin film: Surface spin polarization and ferromagnetism

Room temperature ferromagnetism in both transition-metals doped and undoped semiconductor thin films and nanostructures challenges our understanding of the magnetism in solids. In this report, we performed the magnetic measurement and Andreev reflection spectroscopy study on undoped Indium-Tin oxide (ITO) thin films and bulk samples. The magnetic measurement results of thin films show that the total magnetization/cm² is thickness independent. Prominent ferromagnetism signal was also discovered in bulk samples. Spin polarized electron transports were probed on ITO thin film/superconductor interface and bulk samples surface/superconductor interface. Based on the magnetic measurement results and spin polarization measurement data, we propose that the ferromagnetism in this material originates from the surface spin polarization and this surface polarization may also explain the room temperature ferromagnetism discovered in other undoped oxide semiconductor thin films and nanostructures.     

Specific contact resistance of IGZO thin film transistors with metallic and transparent conductive oxides electrodes and XPS study of the contact/semiconductor interfaces

In this work, the specific contact resistance (ρ_c) between amorphous indium-gallium-zinc-oxide (IGZO) semiconductor and different contact electrodes was obtained from thin film transistors (TFTs). Ti/Au (10/100 nm), aluminum doped zinc oxide (AZO, 100 nm) and indium tin oxide (ITO, 100 nm) were used as source/drain electrodes to fabricate IGZO TFTs. Chemical states of the contacts/semiconductor interfaces were examined by depth profile X-ray photoelectron spectroscopy (XPS) analysis to explain the origin of the differences on specific contact resistance. The lowest ρ_c achieved using Ti/Au was related to the formation of a TiO_x interlayer due to oxygen atoms diffusing out from the semiconductor under layer, increasing the carrier concentration of IGZO at the interface and lowering the ρ_c. On the contrary, no interfacial reactions were observed between IGZO and AZO or ITO source/drain. However, IGZO resistivity increased with ITO contacts likely due to oxygen vacancies filling during ITO deposition. This fact seems to be the origin of the high contact resistance between IGZO and ITO, compared to IGZO-AZO and IGZO-Ti/Au interfaces.     

Effect of antimony doping on the low‐temperature performance of solution‐processed indium oxide thin film transistors

The effects of antimony (Sb) doping on solution‐processed indium oxide (InO_x) thin film transistors (TFTs) were examined. The Sb‐doped InSbO TFT exhibited a high mobility, low gate swing, threshold voltage, and high I_ON/OFF ratio of 4.6 cm²/V s, 0.29 V/decade, 1.9 V, and 3 × 10⁷, respectively. The gate bias and photobias stability of the InSbO TFTs were also improved by Sb doping compared to those of InO_x TFTs. This improvement was attributed to the reduction of oxygen‐related defects and/or the existence of the lone‐pair s‐electron of Sb³⁺ in amorphous InSbO films. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)