不同环境中X射线激光Yb靶表面氧化研究

 用电子束蒸发方法淀积制备X射线激光稀土元素Yb薄膜靶,将薄膜靶在不同的环境气氛中进行氧化。用X射线光电子谱(XPS)、俄歇电子谱(AES)和X射线衍射(XRD)方法研究了Yb薄膜靶表面氧化层的元素价态、组分和微观结构。发现薄膜表面氧化层中存在分层结构,干燥空气中储存的Yb薄膜表面氧化层由表及里的组分依次为化学吸附水、氢氧化物、氧化物及金属元素。表面氢氧化物和氧化物以非晶态形式存在。潮湿空气中水分是薄膜靶氧化速率增加的主要原因。     

X射线激光Nd薄膜靶表面氧化特性研究

 利用石英晶体振荡技术测量了不同环境中稀土元素Nd薄膜靶表面氧化速率,用俄歇电子能谱,扫描电镜,X射线衍射,X射线光电子能谱分析了Nd薄膜表面氧化过程,发现保存环境对靶的表面氧化行为有重要影响。空气中水分是引起Nd快速氧化的关键因素。表面氧化层为团聚状的非晶结构,氧化物与金属的体各比较小可能是引起Nd薄膜较易氧化的原因。Nd薄膜靶表面覆盖有一层氢氧化物,其厚度按保存在真空、干燥空气和潮湿空气环境而依次递增。     

类Ni-NdX射线激光靶表面氧化研究

用磁控溅射镀膜法制备了Nd靶,研究了Nd靶在不同环境气氛下的氧化过程,并利用X射线光电子能谱、原子力显微镜对表面氧化物的化学态、表面形貌进行了分析和研究,得出Nd靶防氧化主要是防止表面的氢氧化这一结论 关键词：     

氮化铌表面氧化物的XPS研究

本文用X射线光电子能谱(XPS)对室温下自然氧化和射频氧化的氮化铌薄膜表面进行了成分分析。指出:与在类似条件下纯铌膜的氧化不同,NbN膜的表面氧化物中不存在NbO和NbO₂,而是以Nb₂O₃作为从NbN到Nb₂O_5-y的过渡相。氮化铌在氧化过程中表现出一种抑制Nb₂O,NbO等低价传导性氧化物生成的能力,这对于用氧化物作势垒的超导隧道结的研制具有实际参考价值。 关键词：     

Fe/ZnO (0001)体系界面相互作用中薄膜厚度效应的光电子能谱研究

利用同步辐射光电子能谱(SRPES)和X射线光电子能谱(XPS)技术,系统研究了室温下Fe/ZnO界面形成过程中Fe薄膜与氧结尾的ZnO(000 1 )衬底之间的相互作用,结果显示初始沉积的Fe明显被表面氧氧化为Fe²⁺离子,在Fe覆盖度为0—3 nm的范围内,分别观察到与界面电荷传输、化学反应以及薄膜磁性相关的三个有意义的临界厚度,这一结果将有助于基于Fe/ZnO界面的相关器件的设计和研发. 关键词： Fe/ZnO 界面作用 同步辐射光电子能谱 X射线光电子能谱     

单晶Si表面离子束溅射沉积Co纳米薄膜的研究

采用离子束溅射沉积法，在单晶Si基片上制备了不同厚度(1—100nm)的Co纳米薄膜.利用原子力显微镜、X射线光电子能谱(XPS)仪和X射线衍射仪对不同厚度的Co纳米薄膜进行了分析和研究.结果表明：当薄膜厚度为1—10nm时，沉积颗粒形态随薄膜厚度增加将由二维生长的细长胞状过渡到多个颗粒聚集成的球状.当膜厚大于10nm时，小颗粒球聚集成大颗粒球，颗粒球呈现三维生长状态.表面粗糙度随膜厚的增加呈现先增加后减小的趋势，在膜厚为3nm时出现极值.XPS全程宽扫描和窄扫描显示：薄膜表面的元素成分为Co，化学态分别 关键词： 离子束沉积 纳米薄膜 X射线光电子能谱 X射线衍射     

GaAs(100)表面硫钝化的新方法:CH3CSNH2/NH4OH处理

建立了一种硫钝化GaAs(100)表面的新方法,即CH₃CSNH₂/NH₄OH溶液处理,应用同步辐射光电子能谱(SRPES)和X射线光电子能谱(XPS)表征了该钝化液处理的n-GaAs(100)表面的成键,特性和电子态.结果表明,经过处理的n-GaAs(100)表面,S既与As成键也与Ga成键,形成S与GaAs的新界面,并且Ga和As的氧化物被移走,这标志着CH₃CSNH₂/NH_{4关键词：}     

Ti/AIN陶瓷界面反应的光电子能谱研究

用X射线光电子能谱(XPS)研究了在室温和超高真空条件下金属Ti淀积在AlN陶瓷表面上的化学反应过程.在金属Ti淀积之前,从AlN陶瓷的能谱中的Ols和Al2P的结合能可以看到因是样品的主要杂质,而且样品表面部分的Al被氧化.当样品淀积了金属Ti以后,发现刚淀积上去的Ti是氧化状态,还发现在Ti淀积的同时则Nls在高结合能处(402和406eV)出现新峰.随着Ti淀积厚度的增加,Ti低结合能的成份在增加而Al的氧化成份逐渐增加,Nls高结合能处的峰(402和406eV)也逐渐增高,更进一步成为主导地.N在 关键词：     

Fe/ZnO (0001)体系界面相互作用中薄膜厚度效应的光电子能谱研究

利用同步辐射光电子能谱(SRPES)和X射线光电子能谱(XPS)技术,系统研究了室温下Fe/ZnO界面形成过程中Fe薄膜与氧结尾的ZnO(000 1 )衬底之间的相互作用,结果显示初始沉积的Fe明显被表面氧氧化为Fe²⁺离子,在Fe覆盖度为0—3 nm的范围内,分别观察到与界面电荷传输、化学反应以及薄膜磁性相关的三个有意义的临界厚度,这一结果将有助于基于Fe/ZnO界面的相关器件的设计和研发.     

软X射线辐照引起的铟锡氧化物表面光化学反应

利用XPS原位研究了Mg Kα X射线辐照对ITO表面的影响.结果表明,随着X射线辐射时间的延 长,表面辐照区域In,Sn相对含量增加,而O则逐渐减少,同时,In,Sn3d光电子峰随X射线 辐射的增强而变化.分析说明X射线的辐照导致了ITO表面光化学反应,氧的脱离使In,Sn有 被还原的趋势,受损较重的In明显存在亚氧化态.In,Sn俄歇参数的变化进一步证实ITO表面 发生了光化学反应.并讨论了X射线引起ITO表面光化学反应的机制. 关键词： X射线辐照 光电子能谱 光化学反应     

The interaction of H2O molecules with iron films studied with MIES,UPS and XPS

X-Ray Photoelectron Spectroscopy (XPS), Metastable Induced Electron Spectroscopy (MIES) and Ultraviolet Photoelectron Spectroscopy (UPS) were applied to study the interaction of H₂O molecules with iron films.During the interaction with H₂O molecules under ultrahigh vacuum conditions, an oxide film is formed on the iron surface. UPS and XPS still show metallic contributions, even for a surface which is exposed to about 10³ L. The oxide film thickness amounts to about 1.8 nm. No hydroxide formation is observed at all, neither in UPS nor in MIES. Further impinging H₂O molecules do not interact with the surface, because the oxide film inhibits the dissociation of impinging molecules.H₂O exposure beyond 10⁹ L does not lead to a significant increase of the oxide layer, which saturates at a thickness of 1.8 nm. In particular, no surface hydroxide is observed at this exposure. Neither XPS UPS nor MIES reveal any indication for this.     

The reactions of oxygen and water with the rare-earth metals terbium to lutetium studied by x-ray photoelectron spectroscopy

The X-ray excited oxygen 1s photoelectron spectra of water adsorbed on clean evaporated films of the heavy rare-earth metals, terbium to lutetium, is characterised by two peaks: (1) at 531.0 ± 0.5 eV binding energy, and (2) at 533.0 ± 0.5 eV binding energy, assigned respectively to oxide and hydroxide species. Variation of the relative intensities of these peaks with exposure to water leads to the postulate that the oxidation mechanism is island growth with a layer of hydroxide at the surface of the oxide island. At low temperatures, adsorption of water gives two additional peaks: (3) at 534.5 ± 0.5 eV, and (4) at 535.7 ± 0.2 eV, assigned respectively to chemisorbed and condensed water. On adsorption of small amounts of dry oxygen the O 1s spectra exhibit solely peak (1), whose intensity increases with further oxygen treatment to reach a steady value after ～40 L exposure. The kinetics of reaction with oxygen follow a logarithmic relation, once correction is made for the effect of escape-depth on peak intensity. However, ytterbium, with a closed 4f shell in the metallic state, exhibits oxidation characteristics different from the other rare-earth metals; its oxygen 1s intensity increases linearly with exposure, and the steady plateau level is reached sharply rather than asymptotically. Island growth with a limited number of nucleation sites may explain this behaviour.     

XPS depth profiling study on the passive oxide film of carbon steel in saturated calcium hydroxide solution and the effect of chloride on the film properties

X-ray photoelectron spectroscopy (XPS) was used to study the properties of passive oxide film that form on carbon steel in saturated calcium hydroxide solution and the effect of chloride on the film properties. The thickness of the oxide films was determined to be approximately 4 nm and was not affected by the exposure time. Near the film/substrate interface the concentration of the Fe²⁺ oxides was higher than the concentration of the Fe³⁺ oxides; the layers near the free surface of the film mostly contained Fe³⁺ oxides. Chloride exposure decreased the thickness of the oxide films and changed their stoichiometry such that near the film/substrate interface Fe³⁺/Fe²⁺ ratio increased.     

On the problem of water adsorption on alkali halide cleavage planes,investigated by secondary ion mass spectroscopy

In the epitaxial growth of thin metallic films, atomic beam scattering and other work on (001) cleavage planes of alkali halides, the problem of water adsorption (physically or chemically) and its consequences often arose. In this paper (001) planes of LiF, NaF and NaCl were investigated in a UHV apparatus by secondary ion mass spectroscopy (SIMS) under a variety of conditions: air and vacuum cleaved, with and without heat annealing, with and without exposure to water at various crystal temperatures. The main results are: cleaved crystal surfaces are free of water and hydroxide layers even in the submonolayer region under UHV conditions. Water vapour at a partial pressure of 10^?9 Torr will only adsorb on cooled cleavage planes: for LiF below 200 K, for NaF below 250 K and for NaCl below 260 K, the adsorption energy for the fluorides being in the 200 meV region. Thicker layers of adsorbed water on LiF (001) will grow according to the Weber-Volmer mechanism. The formation of hydroxide layers on the fluorides is possible only under extremely forced conditions. Direct evidence is given that the “active sites” for the adsorption of H₂O consist in surplus Li metal atoms on the surface. Heat treatment in UHV at temperatures up to the melting point for several hours removes these active sites and yields crystal surfaces which do not adsorb water even if cooled. Cleavage planes of the water soluble NaCl showed a somewhat different behaviour.     

Room temperature adsorption of water by aluminum thin films

Thin films of aluminum were prepared under ultra-high vacuum conditions in order to investigate the low temperature, low pressure adsorption of water vapor by the aluminum. The kinetics of the water vapor-aluminium reaction have been found to be essentially different than the oxygen-aluminum reaction previously reported. In contrast to the “dry” oxygen uptake kinetics, a plot of the sticking coefficient of H₂O versus the total weight gain of the film indicates that the sticking coefficient of H₂O passes through a maximum. As a result of the present mass adsorption measurements of water by fresh aluminum surfaces and Huber and Kirk's previous contact potential studies of an oxidized aluminum surface upon exposure to water vapor, a model is suggested, based on the simultaneous lateral growth of oxide nuclei and first order adsorption of water dipoles on the growing oxide nuclei surfaces. The model quantitatively describes the kinetics of the mass adsorption of water and also predicts the contact potential behavior of a fresh aluminum surface upon exposure to water vapor. A sticking coefficient of approximately 0.05 is indicated for H₂O on bare aluminum while 0.11 corresponds to the sticking coefficient of water dipoles on the oxide nuclei surfaces.     

Graphene oxide thin film coated quartz crystal microbalance for humidity detection

In this paper, we demonstrated that chemically derived graphene oxide (GO) thin film as a humidity sensitive coating deposited on quartz crystal microbalances (QCMs) for humidity detection. By exposing GO thin film coated QCMs to various relative humidity (RH) environments at room temperature, the humidity sensing characteristics of the QCMs such as sensitivity and linearity, response and recovery, humidity hysteresis were investigated. The experiment results show that GO thin film coated QCMs exhibit an excellent humidity sensing performance. Moreover, the possible humidity sensing mechanism of GO thin film coated QCMs was also investigated by monitoring the crystal's motional resistance change. It is suggested that the frequency response of the QCMs is dependent on water molecules adsorbed/desorbed masses on GO thin film in the low RH range, and on both water molecules adsorbed/desorbed masses on GO thin film and variations in interlayer expansion stress of GO thin film derived from swelling effect in the high RH range.     

The surface hydro-oxidation of LaNiO(3-delta) thin films

The chemical structure and possible hydro-oxidation of LaNiO(3-delta) films were studied by means of tuneable high-energy X-ray photoelectron spectroscopy using synchrotron radiation. It was shown that the hydroxyl-containing phase, located near the film surface, may be attributed to the lanthanum and nickel hydroxide species. The thickness of a hydroxide-enriched layer was estimated from the oxide/hydroxide ratio measured at normal and grazing conditions. The hydroxide layer thickness was about 2 nm for step and/or exponential hydroxide spatial distribution.     

Characterization and structure study of the anodic oxide film on Zircaloy-4 synthesized using NaOH electrolytes at room temperature

Thick crystalline zirconium oxide films were synthesized on Zircaloy-4 substrates by anodic oxidation at room temperature in NaOH solution with a stable applied voltage (300 V). The film is approximately 4.7 μm in thickness. The XPS and SEM analysis shows that the film is a three-layer structure in water, hydroxide and oxide parts. The thickness of that order is ∼0.01 μm, ∼1 μm, ∼3.7 μm, respectively. The oxide layer is composed of tetragonal and monoclinic phases with the volume ratio about 0.2. Furthermore, the thick anodic film acts as a barrier to oxygen and zirconium migrations. It effectively protects zirconium alloys against the worse corrosion. An extremely low passive current density of ∼0.018 μA/cm² and a low oxidation weight gain of ∼0.411 mg/cm² were also observed in the films.