纳米晶钛膜中氦注入的保持剂量

在从室温到500℃的温度范围内，用卢瑟福质子背散射技术分别测量了不同能量、不同剂量注入的纳米晶钛膜中氦的浓度分布，不同温度时的保持剂量及其释放浓度.发现氦在这种纳米晶粒膜中其氦-钛原子浓度比达到41%—52%时能在室温到100℃的温度下长期稳定保持，若其原子浓度达52%—74%时也能在室温环境有效保持.文中对这种具有大的界面体积比的膜能有效保持氦这种惰性元素的可能机理从能量观点进行了初步探讨. 关键词： 离子注入 纳米晶粒钛膜 氦 保持剂量     

Magnetic properties of magnetite thin films close to the Verwey transition

Temperature dependence of the magnetic properties of magnetite thin film across the Verwey transition has been investigated. As the temperature is decreased, the magnetization of the film in a fixed field showed a sharp decrease close to the Verwey transition temperature (T_v). The M–H loops of the film have been recorded at various temperatures below and above T_v. It is found that film does not saturate at any temperature and saturation becomes more difficult below T_v. While cooling through T_v, the extrapolated value of magnetization to infinite field (Q), calculated from the numerical fit 4πM=Q [1−(H*/H)^1/2], does not show a drop, but the coefficient indicating difficulty in saturation (H*) shows a sharp rise as does the coercivity.     

A magnetron sputtering technique to prepare a-C:H films: Effect of substrate bias

Amorphous hydrogenated carbon (a-C:H) films were deposited by magnetron sputtering with a mixture gas of Ar and CH₄. The a-C:H films deposited by this method have relatively low internal stress (<1 GPa) compared to some films deposited by conventional deposition process. The effects of substrate bias voltage on microstructure, surface morphology and mechanical properties of the films were investigated by various techniques. It has been found that the polymer-like structure is dominated at low bias voltage (−100 V), while the diamond-like structure with the highest hardness and internal stress is the main feature of the a-C:H films deposited under high bias voltage (−300 V). With increasing the bias voltage further, the feature of diamond-like structure decreases associating with the increase of graphitization. The frictional test shows that the friction coefficient and wear rate of the a-C:H films are depended strongly on structure and mechanical properties, which were ultimately influenced by the deposition method and bias voltage.     

Surface modification of gold nanoparticles and their monolayer behavior at the air/water interface

Gold nanoparticles were prepared by two different methods. The first method was chemically grafting the particles with different lengths of alkylthiol (C₆SH, C₁₂SH and C₁₈SH). For the second method, the Au particles were surface modified first by mercaptosuccinic acid (MSA) to render a surface with carboxylic acid groups which play a role to physically adsorb cationic surfactant in chloroform. This method was termed physical/chemical method. In the first method, the effects of alkyl chain length and dispersion solvent on the monolayer behavior of surface modified gold nanoparticles was evaluated. The gold nanoparticles prepared by 1-hexanthiol demonstrated the narrowest size distribution. Most of them showed narrower particle size distributions in chloroform than in hexane. For the physical/chemical method, the particles can spread more uniformly on the water surface which is attributed to the amphiphilic character of the particles at the air/water interface. However, the particles cannot pack closely due to the relatively weak particle-particle interaction. The effect of alkyl chain length was also assessed for the second method.     

A simple method to tailor spherical nanocrystal hydroxyapatite at low temperature

A simple method, chemical precipitation at low temperature from Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄ to tailor single phase, highly crystalline nanocrystal hydroxyapatite (HAp) powders was introduced in this paper. HAp powders with controlled morphologies (spherical and rod-like) and different grain sizes have been obtained by varying the reaction temperature, reaction mode, and heat treatment accordingly. X-ray diffraction (XRD) results combined with the Fourier transform-infrared spectroscopy (FT-IR) indicates that the single phase, nanocrystal HAp powder could be obtained in one-step without further heat treatment. At 40 °C with a quick mixing mode, ultra-fine complete spherical HAp particles with diameter range size of 20–50 nm could be obtained.     

Preparation and magnetic properties of magnetite nanoparticles by sol–gel method

 Magnetite (Fe₃O₄) nanoparticles have been successfully synthesized by sol–gel method combined with annealing under vacuum. The phase structures, morphologies, particle sizes, chemical composition, and magnetic properties of Fe₃O₄ nanoparticles have been characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectrometer and vibrating sample magnetometer (VSM). The results indicate that the size, the corresponding saturation magnetization value and coercivity value of Fe₃O₄ nanoparticles increase with the increase of synthesized temperature. And the phase transformation of Fe₃O₄ nanoparticles has been studied under different atmospheres and temperatures.     

A simple technique to deposit molybdenum thin films

A simple technique is proposed for metallizing nonconductive objects. The technique, which is based on a plasma-induced dissociation of Mo(CO)₆ molecules, is inexpensive with no sophisticated instrument needed, and allows us to deposit fine grained, adherent thin films of molybdenum on nonrefractory substrates. It is believed that the technique possesses a variety of potential applications in laboratory works.     

Reflectivity of cadmium sulphide nanocrystal films grown by the Langmuir–Blodgett technique

0 ) in the reflectivity spectra has been found to be blue-shifted with respect to that for bulk CdS. The appearance of the E₁(A) peak at about 5 eV is evidence for the hexagonal nature of the particles with the c axis normal or nearly normal to the plane of the film. This suggests the epitaxial nature of the grown particulate films. Another reflectivity peak has been observed at about 320 nm. However, its origin is not yet clear. Received: 26 May 1998/Accepted: 28 May 1998     

Stability of the magnetic domain structure of nanoparticle thin films against external fields

We investigate the effect of external magnetic fields on the magnetic structure of thin films from magnetic nanoparticles (MNP) with dipolar interaction. Such fields are present, for example, if samples are scanned with magnetic probes. Numerical simulations and experimental magnetic force microscopy (MFM) studies are presented. Numerically, we have calculated the magnetization pattern of single-layer and multilayer MNP thin films. The calculations show that unperturbed single-layer MNP films have an in-plane orientation of the magnetization with a flux-closure-domain pattern. An external field generated by a point dipole above the film induces locally an out-of-plane configuration of the magnetization. In the corresponding MFM images, the domain pattern in the film is erased and a stripe-like contrast enhancement at the edges appears. Multilayer films are found to be more robust against external fields than monolayers.     

超导薄膜磁场穿透深度的双线圈互感测量

磁场穿透深度是联系超导体宏观电动力学与微观机制的重要物理量,其精确测量对于研究超导机理以及探索超导应用具有重要意义.在众多的磁场穿透深度测量方法中,双线圈互感法具有测量精度高、技术相对成熟、对样品没有破坏等优点,可被用于细致地研究超导薄膜的磁场穿透深度对温度、掺杂、外延应力等参量的依赖关系.本文首先简要介绍了双线圈互感法的基本原理,指出该方法的测量精度主要受系统几何参数及薄膜边缘漏磁的影响;之后对自主设计搭建的透射型双线圈互感装置进行了系统的校验,并详细说明了其测量精度:对于厚度为100 nm,穿透深度为150 nm的典型薄膜样品,穿透深度绝对值的测量误差小于10%;最后通过测量NbN超导薄膜的磁场穿透深度进一步检验了装置的精度,分析表明穿透深度的测量值与文献报道结果符合.     

水热法制备TiO2薄膜的研究

采用水热法在玻璃基片上制备了TiO2薄膜.利用x射线衍射(XRD)、x射线光电子能谱(XPS)、扫描电子显微镜(SEM)等分析测试手段对所制备的TiO2薄膜的相结构、表面化学组成及形貌等进行了分析和表征,研究了不同水热条件对所制备TiO2薄膜的光吸收特性的影响.结果表明,所制备的薄膜为锐钛矿型TiO2,均匀、致密、无可视缺陷,具有优异的可见光透过性和紫外吸收特性 关键词： 水热法 TiO2薄膜 比消光度     

Thin films of polyaniline deposited by MAPLE technique

Polyaniline (PAni) has important electro-conductive properties, high absorbance in microwave range and it is also frequently used in gas sensors because of its capability to convert chemical interactions into electrical signals. The methods of obtaining polyaniline in the form of thin films and/or nanostructures are complicated and request special physical and chemical treatments, both on the substrate surface and for the polymer itself.In this paper we applied matrix assisted pulsed lased evaporation (MAPLE) for obtaining thin films and nanostructures of polyaniline. In MAPLE, the target consisting of the material (usually 0.2-3 wt%) dissolved in a solvent is frozen and it is evaporated using a laser. In our case polyaniline-emeraldine salt (PAni-ES) was dissolved in xylene or toluene, frozen in liquid nitrogen and was used as target. The third and the fourth harmonics of a Nd-YAG laser (λ = 355 nm and 266 nm) were used as laser sources. The obtained films have been characterized by atomic force microscopy, dielectric spectroscopy and Fourier transform infrared spectroscopy. The influence of the solvent type and of the laser parameters (wavelengths and fluence) on the polyaniline structures composition and properties has been investigated.     

利用多层膜生长技术制备纳米印章模板

在纳米印章技术中，为克服电子束刻蚀制备50nm以下线条的技术难点，利用等离子增强化学 气相沉积技术制备了a-Si/SiN_x多层膜，再利用选择性湿法腐蚀或干法腐蚀在横 截面上制备出浮雕型一维纳米级模板. 多层膜子层之间界面清晰陡峭，可以在纳米量级对子 层厚度进行控制，得到了侧壁在纳米尺度上平滑的模板. 通过控制多层膜子层的生长时间， 制备出线条宽度和槽状宽度均为20nm的等间距模板，品质优于电子束刻蚀技术制备的模板. 关键词： 纳米印章模板 多层膜生长技术     

Superconducting Nd1.85Ce0.15CuO4 films grown by the pulsed electron deposition technique

Nd_1.85Ce_0.15CuO_4−δ superconducting thin films were prepared on (1 0 0) SrTiO₃ substrates by pulsed electron deposition technique without reducing atmosphere. Oxygen content is finely controlled by high temperature vacuum annealing, and optimal superconductivity has been obtained. The deposition conditions of the film are discussed in details. Higher deposition temperature and lower gas pressure result in the loss of copper and the appearance of the foreign phase Ce_0.5Nd_0.5O_1.75. High quality Nd_1.85Ce_0.15CuO_4−δ epitaxial films are deposited at 840–870 °C in the mixed gas with a ratio of O₂:Ar = 1:3.     

硬脂酸单分子膜上电沉积Ag膜的研究

通过电沉积方法 ,以气 /液界面上形成的硬脂酸单分子膜为模板诱导沉积金属银膜 .考察了镀液 pH值、单分子膜表面压及沉积电位对银膜形貌及结构的影响 .实验发现 ,酸性镀液的气 /液界面上形成的单分子膜不能诱导沉积银 ,而在中性和碱性镀液的气 /液界面上可以诱导银膜的生长 .当单分子膜处于液态或固态时 ,气 /液界面有银膜形成 ;液态单分子膜上的银膜生长速度较快 ,且银膜的结构一致 .随着电极电位的升高 ,银膜沉积的速度加快 ,呈环状向外生长的圆形银膜逐渐变得不规则 .将不同实验条件下的银膜转移出来 ,采用扫描电镜 (SEM )、透射电镜 (TEM )对银膜的结构与形貌进行了表征 .研究表明 ,银首先在单分子膜上异相成核 ,由八面体构型逐渐发展成星型 ,最终在气 /液界面形成具有松枝状微观结构的光亮银膜 .     

Development of band patterns in surface films: A simple theory

Semiconductor technology often employs thin films deposited on crystal surfaces, and in some cases these films can self-organize into band, ring or spiral patterns during annealing. A simple theory is proposed which predicts the stability or instability of such films and, in the case of instability, the band spacing, which depends upon bulk, surface and interfacial free energies. This information could be of use in self-assembly techniques. In some cases, bands condense into particle arrays upon further annealing, and a theoretical model is developed to predict the subsequent evolution of circular band patterns by diffusion, which causes the regular disappearance of alternate bands.     

椭圆偏振技术研究VHF-PECVD高速沉积微晶硅薄膜的异常标度行为

采用VHF-PECVD技术高速沉积了不同生长阶段的微晶硅薄膜,通过椭圆偏振技术研究了生长过程中微晶硅薄膜表面粗糙度的演化.实验结果表明,沉积气压P_g=300 Pa时,β=0.81,其超出标度理论中β最大值为0.5范围,出现异常标度行为.这表明微晶硅薄膜高速生长中还存在其他粗糙化增加的因素,此粗糙化增加的因素与阴影作用有关. 关键词： 微晶硅薄膜 椭偏光谱法 生长机制 表面粗糙度     

A simple technique for the pyrosol process and deposition of tin oxide films

A very simple and low-cost device for the deposition of thin films by the pyrosol process has been designed Doped and undoped transparent conducting SnO₂ films have been prepared on glass substrates The films obtained were nonstoichiometric but homogeneous and polycrystalline in nature It is found that an activation energy of about 0 2 eV is associated with the film growth process The logarithm of the film thickness varies approximately linearly with the deposition time, and the sheet resistance shows a size effect below a thickness of about 0 3 micro m Doping increases the conductivity but at the cost of transparency The best compromise between transparency and conductivity was obtained at a substrate temperature of about 380°C and with 1 6 mole percent of Sb or 13 mole percent of F as dopants in the as-deposited condition The figure of ment of these films is compared to those of films obtained earlier by the spray pyrolysis method F doping produces better results than Sb doping.