Influence of sputtering power on properties of ZnO thin films fabricated by RF sputtering in room temperature

High mobility and c-axis orientated ZnO thin films were deposited on glass substrates using RF sputtering method at room temperature.Structural properties of ZnO thin films were investigated by X-ray diffraction (XRD).Surface morphology and roughness were studied with scanning electron microscopy (SEM) and atomic force microscopy (AFM).Electrical properties were measured at room temperature using a Hall effect measurement system.The influence of sputtering power on characteristics of ZnO thin films is studied.The results indicate that the sputtering powers have great influence on the crystal quality and mobility of ZnO thin films.By using optimized sputtering conditions,high crystal quality ZnO thin films with Hall mobility of 34 cm 2 /V·s at room temperature were obtained.     

Oxide engineering of ZnO thin‐film transistors for flexible electronics

Abstract— In this paper, we show that ZnO thin‐film transistors (TFTs) are potentially a higher performance alternative to organic and amorphous‐Si TFTs for macroelectronics on plastic substrates. Specifically, we fabricated nanocrystalline ZnO thin‐film transistors using low‐temperature processing, compatible with flexible electronics on plastic substrates. The ZnO semiconductor was rf magnetron sputtered, and the Al₂O₃ gate dielectric was deposited either by electron‐beam evaporation or atomic layer deposition. By controlling the partial pressure of oxygen pO₂) during ZnO sputtering, we could engineer the field‐effect mobility of ZnO transistors to be between 2 and 42 cm²/V‐sec, attractive for high‐performance electronic applications. We contend that pO₂ controls the oxygen‐vacancy content or stoichiometry of ZnO, and that allows control of transistor field‐effect mobility. Although most of the devices described here were fabricated on Si substrates, devices we made on a thin (50 μm thick) polyimide substrate had about equivalent performance, affirming the compatibility of our processes with plastic substrates. Finally, we show that properties of our nanocrystalline ZnO transistors can be explained by transport models that account for grain‐boundary trapping of mobile carriers.     

Electron‐beam deposition of MgO on plastic substrate and manufacturing flexible flat fluorescent lamp

Abstract— A flexible fluorescent lamp that utilizes the same plasma discharge mode as in PDPs has been manufactured. The structure of the flexible lamp is simple and easy to manufacture. All‐plastic materials including plastic substrates, barrier ribs (spacers), and sealants for low‐temperature manufacturing processing have been adopted except for the phosphor and MgO thin film. The MgO thin films were coated on the plastic substrates as a protection layer against the plasma discharge. The adhesion and biaxial texture of MgO thin film deposited on the plastic substrates, poly‐ethyle‐nenaphthalate (PEN) and polycarbonate (PC), at low temperature (100–180°C) has been characterized. The MgO film on PEN shows good adhesion under a repeated bending test. The manufactured flexible lamp consists of two plastic substrates of about 3 in. on the diagonal, barrier rib (spacer), and external ITO electrodes. The Ne‐Xe (5%) gas mixture at 100–200 Torr was used for the discharge gas. A maximum surface luminance of about 100 cd/m² was achieved for a 1 ‐kHz AC pulse.     

射频磁控溅射法在玻璃基片上沉积CeO2 薄膜的研究

二氧化铈具有高折射率、介电常数和紫外吸收率,因此它广泛地应用于各种光学和电子器件.本文采用射频磁控溅射法在玻璃基片上沉积CeO2薄膜.溅射过程中,首先制备纯二氧化铈靶材,然后在不同的功率上调节不同的基片温度进行溅射.采用光电子能谱、X射线衍射、拉曼光谱和扫描电镜等测试方法表征薄膜的特性.     

Novel top‐gate zinc oxide thin‐film transistors (ZnO TFTs) for AMLCDs

Abstract— High‐performance top‐gate thin‐film transistors (TFTs) with a transparent zinc oxide (ZnO) channel have been developed. ZnO thin films used as active channels were deposited by rf magnetron sputtering. The electrical properties and thermal stability of the ZnO films are controlled by the deposition conditions. A gate insulator made of silicon nitride (SiN_x) was deposited on the ZnO films by conventional P‐CVD. A novel ZnO‐TFT process based on photolithography is proposed for AMLCDs. AMLCDs having an aperture ratio and pixel density comparable to those of a‐Si:H TFT‐LCDs are driven by ZnO TFTs using the same driving scheme of conventional AMLCDs.     

磁控溅射功率对掺Al氧化锌薄膜特性的影响

利用射频磁控溅射技术在石英玻璃衬底上制备掺Al氧化锌(AZO)薄膜,研究了不同溅射功率(75,120,160,200W)对AZO薄膜的结构、光学和电学特性的影响.结果表明:所制备的AZO薄膜具有良好的c轴择优取向,且随着溅射功率的增加,薄膜的表面颗粒尺寸逐渐增加;薄膜在可见光范围具有较高的透射率,吸收边在350～400...     

射频磁控溅射功率对Ni-Mn-Ga薄膜成分与形貌的影响

采用射频磁控溅射镀膜技术在P型Si(100)基片上沉积Ni-Mn-Ga薄膜.实验结果表明,射频溅射功率对Ni-Mn-Ga薄膜成分与形貌有显著地影响.Ni含量随溅射功率的升高呈先增加后减少的趋势,Mn含量呈先减少后增加的趋势,Ga含量几乎呈线性减少的趋势.薄膜的价电子浓度(e/a)变化较小.参考英国国家物理实验室数据中有...     

Impact of bending on flexible metal oxide TFTs and oscillator circuits

Thin‐film circuits on plastic capable of high‐frequency signal generation have important applications in large‐area, flexible hybrid systems, enabling efficient wireless transmission of power and information. We explore oscillator circuits using zinc‐oxide thin‐film transistors (ZnO TFTs) deposited by the conformal, layer‐by‐layer growth technique of plasma‐enhanced atomic layer deposition. TFTs on three substrates—glass, 50‐µm‐thick freestanding polyimide, and 3.5‐µm‐thick spin‐cast polyimide—are evaluated to identify the best candidate for high‐frequency flexible oscillators. We find that TFTs on ultrathin plastic can endure bending to smaller radii than TFTs on commercial 50‐µm‐thick freestanding polyimide, and their superior dimensional stability furthermore allows for smaller gate resistances and device capacitances. Oscillators on ultrathin plastic with minimized parasitics achieve oscillation frequencies as high as 17 MHz, well above the cutoff frequency f_T. Lastly, we observe a bending radius dependence of oscillation frequency for flexible TFT oscillators and examine how mitigating device parasitics benefits the oscillator frequency versus power consumption tradeoff.     

The electrical and optical properties of AZO thin film under different post-annealing temperatures

In this study, the Aluminum element doped zinc oxide (Al:ZnO) thin film was deposited on the Corning glass substrate by RF magnetron sputtering technology and annealing treatment. After sputtering, all thin films are then annealed on nitrogen atmosphere and temperature of 300, 500 and 550 °C, respectively. The structural, electric and optical characteristics were then investigated. All films illustrate strong (002) for ZnO and (335) for Al preferential orientation by using XRD analysis. The lower resistivity can be observed at nitrogen annealing and temperature of 400 °C. The transmittance property of AZO thin film exhibited an excellent transparency in the visible light range. The transmittance reached to nearly 81.4 % for all Al:ZnO film. It can be clearly observed that the grain size of AZO thin film is very uniform by utilizing SEM technology.     

氧化锌纳米棒/单晶硅的酒精传感器研究

首先采用射频溅射在单晶硅(Si)上制备氧化锌(ZnO)薄膜,作为生长ZnO纳米棒的晶种层,再在水热条件下生长ZnO纳米棒.X射线衍射、X射线能量色散谱,扫描电镜及室温光致发光谱对样品的物相结构、成分、表面微观形貌和晶体缺陷进行了表征.结果表明合成的ZnO纳米棒是六方纤锌矿结构,长径比较高,结晶良好.研究了ZnO纳米棒/单晶Si传感器在空气和酒精气体中的电压-电流(Ⅰ-Ⅴ)特性,阻抗谱及响应-恢复时间.该传感器在+6 V的偏置电压下,其电阻在0.08 g/L酒精气体中下降71%,响应时间小于1 min,可以作为一种新型的酒精气体传感器.     

Fabrication of IZO transparent conducting thin films by the use of magnetron sputtering equipped with ion‐beam system

Abstract— Indium zinc oxide (IZO) thin films have been prepared on glass, polycarbonate (PC), and polyethylene terephthalate (PET) substrates by using a radio‐frequency (RF) magnetron sputtering system equipped with an ion gun, and a simple OLED device was made by using IZO film. The influence of the RF power, the Ar gas volume, and the substrate temperature during the deposition process on the roughness and the electrical and optical properties of the films have been investigated. In addition, End‐Hall ion‐beam treatment of the substrates is applied before the sputtering deposition process. The sheet resistance of the IZO films is 25 Ω/□ for the glass, 21 Ω/□ for the PC, and 20 Ω/□ for the PET substrate with a thickness of 150 nm, and the lowest root‐mean‐square (rms) roughness of these IZO films were measured to be 0.58, 0.35, and 0.32 nm for glass, PC, and PET substrate, respectively. The decrease in the sheet resistance of the IZO films becomes evident after the ion‐beam treatment and makes the surface of the thin film more hydrophilic. Relative to non‐treated IZO film, the ion‐beam‐treated IZO anode in the OLED device seems to inject holes into the emitting layer to enhance the current density.     

ZnO系薄膜对NOx气体的气敏光透射特性

用射频磁控溅射方法制备了纯氧化锌（ＺｎＯ）薄膜和掺Ａｇ、掺Ｐｔ与掺Ｐｄ的ＺｎＯ三种气敏光学薄膜。测量了这些薄膜在ＮＯｘ气体中的透射光谱,然后由透射光谱获得了灵敏度的变化规律,并用吸附平衡关系式解释了气敏光透射特性,最终优化得到一种对ＮＯｘ气体灵敏度高的掺Ａｇ氧化锌薄膜。     

Magnetic lithography for servowriting applications using flexible magnetic masks nanofabricated on plastic substrates

Magnetic lithography (ML) is a process qualitatively analogous to contact optical lithography which transfers information from a nanopatterned magnetic mask (analog of optical photomask) to magnetic media (analog of photoresist), and is interesting for applications in instantaneous parallel magnetic recording, in particular for servowriting applications. The magnetic mask consists of nanopatterned magnetically soft material (FeNiCo, FeCo) on a thin flexible plastic substrate, typically Polyethylene teraphtalate (PET) or polyimide. When uniformly magnetized media is brought into intimate contact with the magnetic mask, an externally applied magnetic field selectively changes the magnetic orientation in the areas not covered with the soft magnetic material. Flexible substrate of the magnetic mask offers superior compliance to magnetic media which is likely to have imperfect flatness and surface particulate contamination. We discuss nanofabrication challenges of magnetic masks on plastic substrates, including electron beam lithography, electroplating and lift-off processing on the nanometer scale, adhesion of metal thin films on PET and polyimide substrates, and release of plastic films from rigid substrates used during the processing. We present results on fabricated magnetic masks, magnetic force microscopy images of the magnetic transition patterns and disk spinstand tests of servowritten patterns.     

Room temperature ferromagnetism of Ni, (Ni, Li), (Ni, N)-doped ZnO thin films

Ni-doped ZnO thin films (Ni concentration up to 10 mol%) were generated on Si (100) substrates by a sol-gel technique. The films showed wurtzite structure and no other phase was found. The chemical state of Ni was found to be bivalent by X-ray photoelectron spectroscopy. The results of magnetic measurements at room temperature indicated that the films were ferromagnetic, and magnetic moment decreased with rise of Ni concentration. The magnetization of Ni (10 mol%)-doped ZnO film annealed in nitrogen was low...     

La掺杂ZnO和SnO2薄膜的气敏特性

真空蒸发沉积薄膜再经热氧化获得n型掺La的ZnO和SnO2薄膜(玻璃衬底)研究掺La含量与热氧化工艺对薄膜的物相结构、表面形貌和气敏特性的影响.实验给出:掺La使薄膜表面颗粒细化,随La含量增加,ZnO,SnO2薄膜平均晶粒尺寸均增大.掺La可明显降低2种薄膜的气敏工作温度相比之下,掺La对ZnO薄膜的灵敏度改善明显优...     

Low temperature deposited titanium boride thin films and their application to surface engineering of microscale mold inserts

Titanium boride thin films were deposited at low temperatures by balanced magnetron sputtering and inductively coupled plasma (ICP) assisted balanced magnetron sputtering. The chemical composition, surface morphology, structure, and mechanical properties of titanium boride thin films were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy, and instrumented nanoindentation. As compared to titanium boride films deposited by balanced magnetron sputtering, the increase in plasma density surrounding the substrate surface during film growth afforded by the ICP assist causes significant film densification and mechanical property improvement. The morphology of titanium boride thin films deposited onto microscale non-flat Ta substrates and their effectiveness as barrier coatings for microscale compression molding of Al was characterized by focused ion beam sectioning and SEM. The present results show the potential of low-temperature deposited, conformal, titanium boride thin films for engineering surfaces of microscale mold inserts for microscale pattern replication in reactive metals by compression molding.     

LPG sensing properties of ZnO films prepared by spray pyrolysis method: Effect of molarity of precursor solution

Nanocrystalline ZnO films were deposited onto glass substrates by spray pyrolysis of zinc nitrate solutions and used as a liquid petroleum gas (LPG) sensor. The dependence of the LPG sensing properties on the molar concentration of zinc nitrate solutions was investigated. The ZnO films were oriented along (0 0 2) with the hexagonal crystal structure. The grain size and grain density increased with an increase in molar concentration of zinc nitrate solutions. The gas sensing properties for LPG of the ZnO films for LPG with different grain sizes were measured at different temperatures. The maximum sensitivity of 43% at the operation temperature of 673 K was found for the ZnO film prepared by spraying a 0.1 M solution. The ZnO thin films exhibited good sensitivity and rapid response–recovery characteristics to LPG. Further, it has been shown the gas sensitivity of the ZnO gas sensor depends upon its grain size.     

Temporary bond—debond technology for high‐performance transistors on flexible substrates

Abstract— A processing technology based upon a temporary bond—debond approach has been developed that enables direct fabrication of high‐performance electronic devices on flexible substrates. This technique facilitates processing of flexible plastic and metal‐foil substrates through automated standard semiconductor and flat‐panel tool sets without tool modification. The key to processing with these tool sets is rigidifying the flexible substrates through temporary bonding to carriers that can be handled in a similar manner as silicon wafers or glass substrates in conventional electronics manufacturing. To demonstrate the power of this processing technology, amorphous‐silicon thin‐film‐transistor (a‐Si:H TFT) backplanes designed for electrophoretic displays (EPDs) were fabricated using a low‐temperature process (180°C) on bonded‐plastic and metal‐foil substrates. The electrical characteristics of the TFTs fabricated on flexible substrates are found to be consistent with those processed with identical conditions on rigid silicon wafers. These TFTs on plastic exhibit a field‐effect mobility of 0.77 cm²/V‐sec, on/off current ratio >10⁹ at Vds = 10 V, sub‐threshold swing of 365 mV/dec, threshold voltage of 0.49 V, and leakage current lower than 2 pA/μm gate width. After full TFT‐array fabrication on the bonded substrate and subsequent debonding, the flexible substrate retains its original flexibility; this enables bending of the EPD display without loss in performance.     

对靶磁控溅射制备VO_x薄膜及其退火研究

利用对靶磁控溅射法在玻璃基片上制备VOx薄膜,采用正交实验方法研究了镀膜条件对VOx薄膜电阻温度系数(TCR)的影响,得到优化的镀膜工艺参数,主要包括Ar∶O2为48∶0.4、工作压力恒定为2 Pa、基底的温度为室温27℃、溅射功率保持在180W,在此基础上,进行不同温度条件的真空退火,得到薄膜TCR在-2.5%~-4.5%范围。利用原子力显微镜(AFM)和X射线光电子能谱法(XPS)分析了退火对提高薄膜TCR的作用,并找出VOx薄膜阻值与TCR的优化组合。同时,还观察到薄膜表面形貌的变化以及退火后薄膜中VO2,V2O3,V2O5的比例变化情况,并对其机理进行解释。     

Highly reliable a‐IGZO TFTs on a plastic substrate for flexible AMOLED displays

We have successfully reduced threshold voltage shifts of amorphous In–Ga–Zn–O thin‐film transistors (a‐IGZO TFTs) on transparent polyimide films against bias‐temperature stress below 100 mV, which is equivalent to those on glass substrates. This high reliability was achieved by dense IGZO thin films and annealing temperature below 300 °C. We have reduced bulk defects of IGZO thin films and interface defects between gate insulator and IGZO thin film by optimizing deposition conditions of IGZO thin films and annealing conditions. Furthermore, a 3.0‐in. flexible active‐matrix organic light‐emitting diode was demonstrated with the highly reliable a‐IGZO TFT backplane on polyimide film. The polyimide film coating process is compatible with mass‐production lines. We believe that flexible organic light‐emitting diode displays can be mass produced using a‐IGZO TFT backplane on polyimide films.