N-Al共掺ZnO薄膜的p型传导特性

利用直流反应磁控溅射技术制得N-Al共掺的p型ZnO薄膜，N2O为生长气氛．利用X射线衍射（XRD），Hall实验，X射线光电子能谱（XPS）和光学透射谱对共掺ZnO薄膜的性能进行研究．结果表明，薄膜中Al的存在显著提高了N的掺杂量，N以N-Al键的形式存在．N-Al共掺ZnO薄膜具有优良的p型传导特性.当Al含量为0.15wt%时，共掺ZnO薄膜的电学性能取得最优值，载流子浓度为2.52e17cm－3，电阻率为57.3Ω·cm，Hall迁移率为0.43cm2/(V·s)．N-Al共掺p型ZnO薄膜具有高度c轴取向，在可见光区域透射率高达90%．     

Ion Beam Analysis of Amorphous and Nanocrystalline Group III-V Nitride and ZnO Thin Films

The ion beam analysis (IBA) techniques of Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA), nuclear reaction analysis (NRA), and particle-induced x-ray emission (PIXE) have been used to quantitatively determine composition, uniformity, impurity, and elemental depth profiles of major, minor, and trace elements of group III-V nitride and zinc oxide (ZnO) thin films prepared by various growth techniques. The IBA revealed that an amorphous GaN film prepared by ion beam assisted deposition (IBAD) has large variations in film thickness and composition coupled with typically 10–20% oxygen that was found to be essential to stabilize their amorphous structure. The IBA characterization of plasma-assisted molecular beam epitaxy (PAMBE) grown GaN, InN, and InCrN films revealed composition, impurity, and uniformity information of the films. The IBA of ZnO films prepared by radio frequency (RF) sputtering showed that the Zn/O ratio often varied significantly over the film thickness. Hydrogen was found to be a major impurity in the films with around one present in the as-deposited ZnO films. It is clearly shown that the nondestructive, quantitative, and rapid IBA measurements are very useful to develop and optimize growth protocols in respect to film thickness, stoichiometry, and especially in regard to hydrogen and oxygen impurities for group III-V nitride and ZnO thin films prepared by various growth techniques.     

Fabrication of p-Type ZnO Thin Films via DC Reactive Magnetron Sputtering by Using Na as the Dopant Source

The Na-doped p-type ZnO thin films were prepared by DC reactive magnetron sputtering. Two types of substrates were used for separate testing purposes: silicon wafers for crystallinity measurements and glass slides for electrical and optical transmittance measurements. The lowest room-temperature resistivity under the optimal condition was 59.9 Ω cm, with a Hall mobility of 0.406 cm² V⁻¹s⁻¹ and a carrier concentration of 2.57 × 10¹⁷ cm⁻³. The Na-doped ZnO thin films possessed a good crystallinity with c-axis orientation and a high transmittance (∼85%) in the visible region. The effects of the substrate temperature on the crystallinity and the electrical properties were discussed.     

改善玻璃衬底上ZnO薄膜特性的方法

利用磁控溅射法在玻璃衬底上淀积铝掺杂氧化锌(AZO)薄膜作为缓冲层,在其上制备了ZnO薄膜。重点研究了AZO薄膜作为缓冲层对玻璃衬底上ZnO薄膜特性的影响。扫描电子显微镜(SEM)图像和X射线衍射(XRD)图谱分析结果表明,玻璃衬底上加入厚度为1μm的AZO缓冲层后,提高了衬底材料和ZnO薄膜之间的晶格匹配程度,有助于增大ZnO薄膜晶粒尺寸,提高其(002)取向择优生长特性、薄膜结晶特性及晶格结构完整性。室温下的透射光谱结果表明玻璃/AZO和玻璃衬底上ZnO薄膜的透光特性没有显著不同。光致发光(PL)谱研究结果表明AZO缓冲层可以有效阻止衬底表面硅原子从ZnO薄膜中"俘获"氧原子,减少ZnO薄膜中的缺陷,改善ZnO薄膜的结晶质量。     

氧化锌纳米线晶体管的电学特性研究

成功制作了氧化锌纳米线沟道场效应晶体管器件,所制作器件的电学性能通过I-V测试进行了分析。使用了水浴法生长了单晶性完整的氧化锌纳米线,该纳米线被用作背栅场效应晶体管的沟道,采用光刻方式制备的器件具有良好的直流特性,进行退火后进一步改善器件的源漏接触,提高器件性能,最终制备成功的场效应晶体管显示出p型MOS的特性,其开关态电流比达到105。在Vds=2.5 V时,跨导峰值为0.4μS,栅氧电容约为0.9 fF,器件夹断电压Vth为0.6 V,沟道迁移率约为87.1 cm2/V.s,计算得到氧化锌纳米线载流子浓度ne=6.8×108 cm-3。在Vgs=0 V时,器件沟道电阻率为100Ω.cm。     

超声雾化气相沉积法制备ZnO薄膜

采用超声雾化气相沉积工艺,以醋酸锌水溶液为前驱体溶液,在SiO2/Si衬底上成功的制备出ZnO薄膜。通过X-射线衍射(XRD)、扫描电镜(SEM)、原子力显微镜(AFM)对所得ZnO薄膜的晶体结构和微观形貌进行分析,发现随着衬底温度升高,ZnO薄膜c轴取向趋势增强,表面趋于光滑平整。研究表明,在前驱体溶液浓度为0.1 mol/L,衬底温度为320℃,载气流量为0.1 L/min,喷口到衬底的距离为60 cm、沉积30 min的实验条件下,生长出的ZnO薄膜为六方纤锌矿结构,且具有的高度c轴取向。     

Al掺杂ZnO薄膜的XPS谱及电学性质研究

采用直流反应磁控溅射法在玻璃基底上用Zn(99.99%)掺杂Al(1.5%)靶制备出高质量的Al掺杂的ZnO(AZO)薄膜。用X射线光电子能谱仪对退火处理后的薄膜进行了成分和元素的价态分析,并用Van der Pauw方法对样品的电学特性进行了测量。实验结果表明,Zn和Al元素都以氧化态的形式存在,O元素主要是以晶格氧和吸附氧的形式存在。AZO薄膜的电学性质受退火温度和氧氩比的影响较大。随着退火温度的升高,电阻率减小,载流子浓度和迁移率增大。随着氧氩比的增大,电阻率增大,迁移率减小。因此可得到用直流反应磁控溅射法制备AZO薄膜的最佳氧氩比和退火温度分别为0.3/27和400℃,在此条件下制备出的薄膜电阻率可低至10-4Ω.cm,载流子浓度可达1020cm-3。     

Relaxing the Conductivity/Transparency Trade‐Off in MOCVD ZnO Thin Films by Hydrogen Plasma

Increasing the conductivity of polycrystalline zinc oxide films without impacting the transparency is a key aspect in the race to find affordable and high quality material as replacement of indium‐containing oxides. Usually, ZnO film conductivity is provided by a high doping and electron concentration, detrimental to transparency, because of free carrier absorption. Here we show that hydrogen post‐deposition plasma treatment applied to ZnO films prepared by metalorganic low‐pressure chemical vapor deposition allows a relaxation of the constraints of the conductivity/transparency trade‐off. Upon treatment, an increase in electron concentration and Hall mobility is observed. The mobility reaches high values of 58 and 46 cm²V^?1s^?1 for 2‐μm‐ and 350‐nm‐thick films, respectively, without altering the visible range transparency. From a combination of opto‐electronic measurements, hydrogen is found, in particular, to reduce electron trap density at grain boundaries. After treatment, the values for intragrain or optical mobility are found similar to Hall mobility, and therefore, electron conduction is found to be no longer limited by the phenomenon of grain boundary scattering. This allows to achieve mobilities close to 60 cm²V^?1s^?1, even in ultra‐transparent films with carrier concentration as low as 10¹⁹ cm^?3.     

ZnO/(Ni)薄膜的制备与发光性能的研究

采用直流磁控溅射法制备了ZnO/(Ni)薄膜.研究了氧分压及Ni掺杂对ZnO薄膜的结构、光致发光特性及薄膜中的几种本征缺陷如氧空位(VO)、锌空位(VZn)、氧位锌(OZn)、锌位氧(ZnO)、间隙氧(Oi)、间隙锌(Zni)等浓度变化的影响.实验结果表明,随着氧分压的增大,466nm处的蓝色发光峰增强,掺Ni后蓝色发光峰也增强.通过分析,推测出蓝色发光峰可能是由ZnO薄膜中的间隙锌(Zni)点缺陷引起的.     

Enhanced Antibacterial Activity of Nanocrystalline ZnO Due to Increased ROS‐Mediated Cell Injury

An innovative study aimed at understanding the influence of the particle size of ZnO (from the microscale down to the nanoscale) on its antibacterial effect is reported herein. The antibacterial activity of ZnO has been found to be due to a reaction of the ZnO surface with water. Electron‐spin resonance measurements reveal that aqueous suspensions of small nanoparticles of ZnO produce increased levels of reactive oxygen species, namely hydroxyl radicals. Interestingly, a remarkable enhancement of the oxidative stress, beyond the level yielded by the ZnO itself, is detected following the antibacterial treatment. Likewise, an exposure of bacteria to the small ZnO nanoparticles results in an increased cellular internalization of the nanoparticles and bacterial cell damage. An examination of the antibacterial effect is performed on two bacterial species: Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive). The nanocrystalline particles of ZnO are synthesized using ultrasonic irradiation, and the particle sizes are controlled using different solvents during the sonication process. Taken as a whole, it is apparent that the unique properties (i.e., small size and corresponding large specific surface area) of small nanometer‐scale ZnO particles impose several effects that govern its antibacterial action. These effects are size dependent and do not exist in the range of microscale particles.     

氧压对ZnO薄膜电阻温度系数的影响

采用脉冲激光沉积(PLD)技术,在不同氧气氛下,在Si(lll)衬底上生长了ZnO薄膜,使用X线衍射仪分析了ZnO薄膜的结晶质量.计算了不同氧气氛下生长的ZnO薄膜的电阻温度系数(TCR)值,发现随着氧分压降低,ZnO薄膜的TCR值增大;ZnO薄膜的TCR值最高可达-8%/K.这为研究ZnO薄膜的导电特性提供了新的途径,开辟了ZnO薄膜在室温非制冷红外微测辐射热计材料中的应用潜力.     

Light Effects on the Bias Stability of Transparent ZnO Thin Film Transistors

We report on the bias stability characteristics of transparent ZnO thin film transistors (TFTs) under visible light illumination. The transfer curve shows virtually no change under positive gate bias stress with light illumination, while it shows dramatic negative shifts under negative gate bias stress. The major mechanism of the bias stability under visible illumination of our ZnO TFTs is thought to be the charge trapping of photo‐generated holes at the gate insulator and/or insulator/channel interface.     

反应压力对MOCVD法沉积ZnO薄膜性质的影响

研究了反应压力对金属有机化学气相沉积(MOCVD)技术制备未掺杂ZnO薄膜的微观结构和光电特性影响.X射线衍射(XRD)和扫描电子镜(SEM)的研究结果表明,随着反应压力的降低,ZnO薄膜(002)择优峰的强度呈现相对减弱趋势,并且出现了较强的(110)峰;Hall测量表明,低的反应压力有助于提高薄膜电学特性.200 Pa时制备出的ZnO薄膜具有明显的"类金字塔"状绒面结构,电阻率为1.28×10-2 Ω·cm.实验中沉积的ZnO薄膜在600～2 600 nm内平均透过率超过80%,而短波长范围由于光散射作用,ZnO薄膜的垂直透过率有所下降.     

掺Al对ZnO薄膜发光性能的调控作用

采用溶胶-凝胶法，在玻璃上制备了不同掺Al浓度的ZnO薄膜。x射线衍射（XRD）结果表明，所制备的薄膜具有c轴择优取向，随着掺Al浓度的增加，（002）峰向低角移动，峰强逐渐减弱。探讨了掺Al对ZnO薄膜发光性能的调控作用，薄膜的透射谱表明：通过改变掺Al浓度，可以提高ZnO薄膜的紫外光透过率，使其吸收边向短波长方向的移动被控制在一定的范围内，从而使薄膜禁带宽度连续可凋；薄膜的光致发光（PL）谱显示：纯ZnO薄膜的PL谱是由紫外激子发光和深能级缺陷发光组成，通过掺Al有助于减少薄膜的缺陷，减弱深能级的缺陷发光，同时紫外带边发射的峰位向高能侧蓝移，与吸收边缘移动的结果相吻合，由紫外发光峰位获得的光禁带与通过透射谱拟合得到的光禁带基本一致。     

Percolation Mechanism and Characterization of (CdO)y(ZnO)1–y Thin Films

(CdO)_y(ZnO)_1–y thin films have been prepared by the sol–gel process, based on precursor solutions used separately for such oxides. The Cd/(Cd + Zn) atomic ratio in solution ranged from 0 to 0.32. These compositions were selected on the basis of an observed abrupt fall, of ca. four orders of magnitude, in the resistivity of the films within this range. Such a resistivity drop, with a threshold value of around y = 0.17, is consistent with a percolation mechanism in a three‐dimensional, random, two‐phase system composed of isotropic, sphere‐like, conducting CdO regions embedded in a highly resistive ZnO matrix. Optical measurements show that the films are highly transparent, above 90 % transmission, for wavelengths ≥600 nm. The optical absorption edge shifts to longer wavelengths as the Cd content in the film increases. On the basis of the percolation mechanism observed in the multicomponent system (CdO)_y(ZnO)_1–y, possible future pathways are proposed for the design and construction of highly efficient, transparent, conducting oxides.     

Phase Segregation in Thin Films of Conjugated Polyrotaxane– Poly(ethylene oxide) Blends: A Scanning Force Microscopy Study

Scanning force microscopy (SFM) is used to study the surface morphology of spin‐coated thin films of the ion‐transport polymer poly(ethylene oxide) (PEO) blended with either cyclodextrin (CD)‐threaded conjugated polyrotaxanes based on poly(4,4′‐diphenylene‐vinylene) (PDV), β‐CD–PDV, or their uninsulated PDV analogues. Both the polyrotaxanes and their blends with PEO are of interest as active materials in light‐emitting devices. The SFM analysis of the blended films supported on mica and on indium tin oxide (ITO) reveals in both cases a morphology that reflects the substrate topography on the (sub‐)micrometer scale and is characterized by an absence of the surface structure that is usually associated with phase segregation. This observation confirms a good miscibility of the two hydrophilic components, when deposited by using spin‐coating, as suggested by the luminescence data on devices and thin films. Clear evidence of phase segregation is instead found when blending PEO with a new organic‐soluble conjugated polymer such as a silylated poly(fluorene)‐alt‐poly(para‐phenylene) based polyrotaxane (THS–β‐CD–PF–PPP). The results obtained are relevant to the understanding of the factors influencing the interfacial and the intermolecular interactions with a view to optimizing the performance of light‐emitting diodes, and light‐emitting electrochemical cells based on supramolecularly engineered organic polymers.     

Effect of Temperature on Structural and Morphologic Properties of ZnO Films Annealed in Ammonia Ambient

ZnO thin films were prepared on Si(111) substrates by pulsed laser deposition (PLD). Then, the samples were annealed at different temperatures in NH₃ ambient and their properties were investigated particularly as a function of annealing temperature. The structure, morphology, and optical properties of ZnO films were studied by x-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), scanning electron microscope (SEM), and photoluminescence (PL). The results show that the increase of annealing temperature makes for the improvement in the crystal quality and surface morphology below the temperature of 650°C. However, when the annealing temperature is above 650°C, the ZnO films will volatilize and, especially at 750°C, ZnO will volatilize completely.