氢等离子体处理对类金刚石膜场发射性能的影响

采用大功率、高重复频率、准分子激光溅射热解石墨靶制备了类金刚石膜,研究了直流辉光氢等离子体处理对类金刚石膜的场发射性能的影响。结果表明:氢等离子体处理后,类金刚石膜的场发射性能明显提高,其发射阈值电场由26V/μm下降到19V/μm。氢等离子体刻蚀除去了类金刚石膜生长表面的富含石墨的薄层,露出的新表面具有较低的功函数;膜表面的悬键被氢原子饱和,进一步降低了电子亲和势,改善了膜的场发射性能。     

氧等离子体刻蚀对石墨烯性能的影响

对机械剥离在SiO2表面的多层石墨烯进行氧等离子体刻蚀,通过拉曼光谱、原子力显微镜和电学性能表征来研究氧等离子体轰击对石墨烯特性的影响。结果表明氧等离子体轰击会在表层石墨烯中引入大量缺陷,大量缺陷的存在又会诱导对石墨烯的进一步刻蚀,从而实现逐层刻蚀石墨烯。另外,氧等离子体轰击的过程在做了金属电极的石墨烯中引入金属颗粒等其它物质,这几方面的原因最终导致在氧等离子体刻蚀石墨烯的过程中石墨烯的两端电导呈现近似线性的减小,石墨烯出现n型掺杂效应。     

氧等离子体对金刚石膜的刻蚀研究

用微波放电法产生氧等离子体，通过改变系统中氧的浓度和金刚石膜的温度研究了氧等离子体对CVD多晶金刚石膜刻蚀的影响。实验结果表明：随着氧浓度的增加和金刚石膜温度的提高，刻蚀作用加剧；而在较低的氧浓度和金刚石膜温度条件下金刚石膜的晶界处首先被刻蚀，说明金刚石膜的境界处含有较多的非金刚石碳相。并且从等离子体对(100)和(111)面的刻蚀现象可知(100)面的生长是二维生长，(111)面的生长是岛状生长。     

氧等离子体处理对氧化铟锡表面化学状态影响的ADXPS研究

利用变角X射线光电子谱对氧等离子体处理前后氧化铟锡ITO薄膜的表面化学状态进行了表征.实验发现用溶剂清洗之后的ITO薄膜表面存在一层厚度大约为0.7nm的非导电碳氢化合物污染层.氧等离子体处理方法可有效地消除C污染,而残存的少量污染C被部分氧化形成含羰基和羧基的化学物种.氧等离子体处理不仅提高了约5.0nm深度范围内的ITO薄膜表层中O的总体含量,更重要的是提高了膜层中O2-离子氧种的含量,改变了膜层化学结构,使得ITO薄膜表面的导电性能降低,同时改善了整个表面层化学结构的均匀性.     

利用激光刻蚀技术提高Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)膜的透氧能力(英文)

利用激光刻图机对Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCFO)透氧膜表面进行刻蚀,以提高膜表面的比表面积,改善膜的氧表面交换能力,从而达到提高透氧量的目的.研究结果表明,激光刻蚀在膜表面形成宽150μm,深25μm的条纹,可以显著提高膜表面的比表面积.XRD图谱显示,激光刻蚀不会引起BSCFO相结构的变化.透氧量测试表明,激光刻蚀可以增大透氧量,十字交叉双面刻蚀效果更加显著.十字交叉双面刻蚀后,其透氧量比未用激光处理的样品提高了大约34%.     

硅化处理对炭纤维石墨化度的影响

对炭纤维在真空炉中进行2100℃硅化处理.用SEM分析了炭纤维在硅化处理前后表面形貌的变化,利用能谱测定了其硅化处理后的成分变化并加以分析,用X射线衍射分析了热处理和硅化处理后的炭纤维石墨化度的变化.结果表明:处理后的炭纤维出现富C的SiC表层,内部为含有SiC的C芯,并伴随有类球状SiC颗粒的形成.沿炭纤维径向分布的SiC含量呈现梯度分布,其芯部的SiC含量为2.46%(质量分数,下同),靠近表层的SiC含量增加到7.53%,表面的SiC含量达到13.25%;纤维表面的类球状颗粒为含C的SiC颗粒,其中SiC的含量为30.55%.在2100℃热处理的炭纤维石墨化度几乎为0,而在2100℃硅化处理的炭纤维石墨化度高达48.5%.     

氧环境扫描电子显微分析:消除绝缘材料荷电效应的新方法

在环境扫描电镜(ESEM)中注入氧气,减少和消除绝缘样品表面在电子束辐照下产生的荷电效应.二次电子像的观察显示,在压力为130Pa～600Pa的ESEM中,氧气对Al2O3、Al(OH)3等氧化物、氢氧化物及生物样品的荷电补偿效果,优于常用的水蒸汽环境.通过吸收电流Ia的实时测试,评价了氧环境的荷电补偿效果.采用氧气减少表面荷电基于一个新的概念:在电子束的辐照下,电子受激解吸可造成表面氧亏损,使能带产生畸变,形成捕获电子的势阱.氧环境提供的氧离子可实现对氧空位的修复,从而消除了荷电效应.     

石墨的微加工工艺研究

石墨具有固态超滑和耐酸、耐碱和耐有机溶剂腐蚀等特性,使其有望成为微机电系统(MEMS)基础材料的一种选择。如能通过微纳米加工工艺对石墨进行微加工并在石墨上大批量、稳定、可控地制备各种掩模图案和石墨微结构,一定程度上可以推动石墨成为MEMS基础材料。故本文通过工艺设计和参数摸索,利用薄膜沉积、光刻、刻蚀等常用的微纳米加工工艺对石墨进行微加工研究,并对加工后的石墨进行表征。结果表明,利用薄膜沉积技术在石墨表面沉积的薄膜可以满足后续光刻和刻蚀等工艺的要求。同时,采用光刻技术能在石墨表面大批量、稳定、可控地加工出不同形状,不同尺寸的光刻胶掩模图案。此外,利用刻蚀技术可以在石墨上大批量、稳定、可控地加工出形状较规则,排列整齐且垂直度较高的石墨微结构。     

氧等离子体处理对氧化铟锡表面化学状态影响的ADXPS研究

利用变角X射线光电子谱对氧等离子体处理前后氧化铟锡ITO薄膜的表面化学状态进行了表征,实验发现用溶剂清洗之后的ITO薄膜表面存在一层厚度大约为0．7nm的非导电碳氢化合物污染层,氧等离子体处理方法可有效地消除C污染,而残存的少量污染C被部分氧化形成含羰基和基的化学物种,氧等离子体处理不仅提高了约5．0nm深度范围内的ITO薄膜表层中O的总体含量,更重要的是提高了膜层中O2－离子氧种的含量,改变了膜层化学结构,使得ITO薄膜表面的导电性能降低,同时改善了整个表面层化学结构的均匀性。     

粒子涂覆法制备超疏水PVDF中空纤维膜

将刻蚀法和超滤涂覆法结合对膜表面进行疏水化处理.对聚偏氟乙烯(PVDF)粒子进行刻蚀,使其表面粗糙化,通过超滤方式将其涂覆在PVDF中空纤维膜表面,构建出微纳米粗糙结构的疏水膜表面,可获得表面接触角为159.7°的超疏水表面,同时膜孔不会被涂覆层堵塞.采用有一定溶解能力的分散液进行超滤涂覆,涂覆层和基膜之间发生溶剂化本体粘接,可明显提高涂覆层牢固性.PVDF粒子最佳刻蚀条件:刻蚀剂溶解度参数为19.11(J/cm~3)1/2,刻蚀时间为20min,温度为35℃.分散液溶解度参数为25.87(J/cm~3)1/2,粒子涂覆量为18.0g/m~2为最优涂覆条件.通过性能测试发现,涂覆膜表现出超疏水特性,同时其透水透气性能与原膜无明显变化.     

不同工艺制备的ta-C和ta-C:N薄膜表面粗糙度研究

采用FCVA工艺成功制备了ta-C薄膜,采用ECR-CVD工艺对部分ta-C薄膜试样进行氮等离子体处理,制备了ta-C:N薄膜.对两种薄膜的表面粗糙度与元素含量、沉积工艺参数之间的关系进行了研究.通过AFM对薄膜表面粗糙度进行了分析,通过XPS对薄膜的元素含量进行了分析.试验结果显示,沉积条件对薄膜厚度和元素含量具有明显的影响.对ta-C薄膜进行氮等离子体处理后,其表面粗糙度有一个明显的起伏变化.研究结果表明,氮能改变DLC薄膜表面的粗糙度.元素含量也随着薄膜的厚度变化而变化.     

超薄四面体非晶碳膜的结构和性能

使用磁过滤阴极真空电弧(FCVA)技术制备不同厚度的超薄四面体非晶碳膜(ta-C)，研究了表征和测量超薄ta-C碳膜微观结构和性能的方法以及膜厚的影响。使用X射线衍射仪验证椭圆偏振光谱仪联用分光光度计表征膜厚度的可靠性并测量了膜密度；用拉曼谱分析薄膜的内在结构，验证用椭偏联用分光光度计表征sp³ C含量的可靠性；用Stoney^，s公式计算了薄膜的残余应力。结果表明，薄膜的厚度由7.6 nm增大到33.0 nm其沉积速率变化不大，为1.7±0.1 nm/min；根据椭偏联用分光光度计的表征结果，薄膜中sp³ C的含量逐渐减少，拓扑无序度降低，与拉曼谱的表征结果一致；厚度为7.6 nm的超薄ta-C碳膜中p³ C的含量最高；随着厚度的增大薄膜中的残余压应力从14 GPa降低到5 GPa；厚度为11.0 nm的薄膜主体层密度最大，为3070 kg/m³，致密性较好；厚度对薄ta-C碳膜表面粗糙度的影响较小。用椭偏和分光光度计测量超薄ta-C碳膜的厚度和表征显微结构是可行的，X射线反射法可用于测量超薄ta-C碳膜密度和表面粗糙度，但是对薄膜的质量要求较高。     

不同厚度四面体非晶碳薄膜的高通量制备及表征

材料基因组工程能大幅度提高材料研发速度, 降低材料研发成本, 近年来受到广泛关注。本研究采用高通量制备工艺, 结合碳等离子体束流和基片位置的调控, 利用自主设计研制的45°双弯曲磁过滤阴极真空电弧设备, 沉积了厚度为4.7~183 nm的系列四面体非晶碳(ta-C)薄膜, 使用椭偏仪、原子力显微镜、拉曼光谱仪和X射线光电子能谱仪(XPS)表征了厚度对ta-C薄膜表面粗糙度、微结构和原子键态的影响。结果表明：通过碳等离子体束流和基片位置的调控, 实现了不同厚度ta-C薄膜的高通量制备。尽管膜厚不同, 所制备的ta-C薄膜均具有几乎不变的光滑表面(R_a=(0.38±0.02) nm)和色散值(Disp(G)), 说明不同厚度ta-C薄膜的sp³含量、sp²团簇尺寸保持相对稳定。XPS结果进一步证实ta-C薄膜的sp³相对含量均维持在(55±5)%。此外, 不同厚度ta-C薄膜的光学带隙E_opt均保持在(1.02±0.08)eV。相关结果为设计制备结构和光学性能可控的不同厚度ta-C薄膜提供了一种新思路。     

Effect of oxygen plasma treatment on bonding states for columnar structured a-CNx thin films prepared by reactive sputtering

Amorphous carbon nitride (a-CN) thin films were deposited on silicon single crystal substrates by rf-reactive sputtering method using a graphite target and nitrogen gas. The substrate temperature was varied from room temperature (RT) to 853 K. After deposition, the effect of oxygen plasma treatment on bonding structures of the film surface has been studied by using an oxygen discharge at 16 Pa and rf power of 85 W. The chemical bonding states and film composition were analyzed by X-ray photoelectron spectroscopy (XPS), while film thickness was obtained from scanning electron microscopy (SEM) and ellipsometer. XPS study revealed that the films have NO₂ and NO₃ bonding structures when the films are deposited at temperatures higher than 673 K. After exposure to oxygen plasma, carbon in the film surface was etched selectively and this phenomenon was observed in all films. In contrast, the surface concentration of nitrogen was ket at constant values before and after oxygen plasma treatment. The NO₃ bonding state had dramatically increased after oxygen plasma treatment for films deposited at higher deposition temperatures. The film surfaces have been observed to change the function from hydrophobic to hydrophilic after oxygen plasma treatment.     

Structural and surface energy analysis of nitrogenated ta-C films

Surface and bulk properties of the Filtered Cathodic Vacuum Arc prepared nitrogenated tetrahedral amorphous carbon (ta-C:N) films were characterized by X-ray Photoelectron Spectroscopy (XPS), Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), Raman spectroscopy, Atomic Force microscopy and contact angle techniques. An increase in the Nitrogen (N) content of the films is accompanied by a reduction in the sp³ fraction, confirmed via the deconvolution of the C 1 s XPS spectra. Critical Raman parameters such as peak position and peak width of the G band, defect ratio, I_D/I_G and skewness of the G line were analyzed as a function of N content. ToF-SIMS showed the variance of chemical composition with the increase in the sputtering depth. While some amount of incorporated oxygen and hydrogen were observed for all films; for high N content ta-C:N films signature of CN bonds was evident. Surface energies (both polar and dispersive components) for these ta-C:N films were analyzed in a geometric mean approach. Contact angle measurements using both deionized water and ethylene glycol reveal that upon the insertion of nitrogen into ta-C films, the initial change in the contact angle is sharp, followed by a gradual decrease with subsequent increase in N content. The variation of contact angle with increasing N content corresponds to an increase of the total surface energy with an increase of the polar component and a decrease of the dispersive component.     

Cobalt-mediated crystallographic etching of graphite from defects

Herein is reported a study of Co-assisted crystallographic etching of graphite in hydrogen environment at temperatures above 750 °C. Unlike nanoparticle etching of graphite surface that leaves trenches, the Co could fill the hexagonal or triangular etch-pits that progressively enlarge, before finally balling-up, leaving well-defined etched pits enclosed by edges oriented at 60° or 120° relative to each other. The morphology and chirality of the etched edges have been carefully studied by transmission electron microscopy and Raman analysis, the latter indicating zigzag edges. By introducing defects to the graphite using an oxygen plasma or by utilizing the edges of graphene/graphite flakes (which are considered as defects), an ability to define the position of the etched edges is demonstrated. Based on these results, graphite strips are successfully etched from the edges and graphitic ribbons are fabricated which are enclosed by purely zigzag edges. These fabricated graphitic ribbons could potentially be isolated layer-by-layer and transferred to a device substrate for further processing into graphene nanoribbon transistors.     

利用氧等离子体预处理增强聚对苯二甲酸乙二醇酯/聚吡咯导电复合薄膜的界面粘附性

首先对聚对苯二甲酸乙二醇酯(PET)薄膜进行氧等离子体预处理,然后通过原位化学氧化聚合法使得吡咯单体在PET薄膜表面沉积聚合,制备了聚对苯二甲酸乙二醇酯/聚吡咯(PET-PPy)复合膜。通过原子力显微镜、X射线光电子能谱仪、ζ电位测试对经不同时长的氧等离子体预处理的PET薄膜进行表征;利用扫描电子显微镜、耐磨性实验和表面电阻测试对PET-PPy复合膜磨损前后的表面形貌和电阻进行分析与表征。结果表明,氧等离子体预处理显著增强了PET-PPy复合膜界面粘附性。氧等离子体预处理使PET薄膜表面粗糙度增大、电负性显著增强。特别地,当预处理时间为120s时,薄膜表面电负性明显增强,此时PET-PPy复合膜磨损后的电阻值变化最小,表明PET薄膜与PPy功能层界面粘附强度得到明显增强。     

氩气流量对四面体非晶碳膜结构和摩擦性能的影响

利用自主研制的45°单弯曲阴极电弧沉积系统,通过改变Ar流量(2,5以及10 ml/min),在p型(100)硅基底上制备了四面体非晶碳膜。借助表面轮廓仪测定薄膜厚度和粗糙度变化;采用X射线光电子谱获得薄膜微结构信息,利用残余应力仪和摩擦磨损试验机测定薄膜的内应力和摩擦学性能。实验结果表明:随Ar流量增加,薄膜的沉积速率降低,表面趋于光滑;薄膜中sp3含量由2 ml/min时的68%下降至10 ml/min时的55%;薄膜应力值随Ar流量的增大而减小,在10 ml/min处取得最小值;不同Ar流量条件下所制备薄膜的摩擦系数在0.024~0.045之间,且随Ar流量增加而增大。     

Tailoring of the morphology and chemical composition of thin organosilane microwave plasma polymer layers on metal substrates

The growth of thin microwave organosilicon plasma polymers on model zinc surfaces was investigated as a function of the film thickness and the oxygen partial pressure during film deposition. The evolution of the topology of the film was studied by atomic force microscopy (AFM). The nano- and micro-roughness was investigated at the inner and the outer surfaces of the plasma polymers. A special etching procedure was developed to reveal the underside of the plasma polymer and thereby its inner surface. Rough films contained voids at the interface, which reduced the polymer/metal contact area. The increase in oxygen partial pressure led to a smoother film growth with a perfect imitation of the substrate topography at the interface. The chemical structure of the films was determined by infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). ToF-SIMS at the outer and the inner surface of the plasma polymers showed that the density of methylsilyl groups increases in the outer surface layer of the plasma polymer and depends on the oxygen partial pressure. The chemical composition of the films could be altered to pure SiO₂ without changing the morphology by using oxygen-plasma post-treatment. This was proved by means of IRRAS and AFM. Chemistry and topology of the films were correlated with the apparent water contact angle. It was found that a linear relationship exists between the nanoscopic roughness of the plasma polymer and the static contact angle of water. Superposition of a nanoscopic roughness of the metal surface and the nanoscopic roughness of methylsilyl-rich films led to ultra-hydrophobic films with water contact angles up to 160°.