脉冲高能量密度等离子体法类金刚石膜的制备及分析

利用脉冲高能量密度等离子体法在光学玻璃衬底上、在室温下成功的制备了光滑、致密、均匀的纳米类金刚石膜.工艺研究表明：放电电压和放电距离以及工作气体种类对纳米类金刚石膜的沉积起着关键作用.利用拉曼光谱、扫描电镜以及电子能量损失谱分析薄膜的形态结构表明：薄膜具有典型的类金刚石特征；纳米类金刚石膜的晶粒尺寸小于20nm甚至为非晶态；类金刚石膜中含有一定量的氮原子，随着沉积能量的升高，氮的含量增大.纳米类金刚石膜的薄膜电阻超过109Ω/cm2.对放电溅射过程进行了理论分析，结果与工艺研究的结论吻合.     

Property improvement of pulsed laser deposited boron carbide films by pulse shortening

Growth characteristics and surface morphology of boron carbide films fabricated by ablating a B₄C target in high vacuum with a traditional KrF excimer laser and a high brightness hybrid dye/excimer laser system emitting at the same wavelength while delivering 700 fs pulses are compared. The ultrashort pulse processing is highly effective. Energy densities between 0.25 and 2 J cm⁻² result in apparent growth rates ranging from 0.017 to 0.085 nm/pulse. Ablation with nanosecond pulses of one order of magnitude higher energy densities yields smaller growth rates, the figures increase from 0.002 to 0.016 nm/pulse within the 2-14.3 J cm⁻² fluence window. 2D thickness maps derived from variable angle spectroscopic ellipsometry reveal that, when ablating with sub-ps pulses, the spot size rather than the energy density determines both the deposition rate and the angular distribution of film material. Pulse shortening leads to significant improvement in surface morphology, as well. While droplets with number densities ranging from 1 × 10⁴ to 7 × 10⁴ mm⁻² deteriorate the surface of the films deposited by the KrF excimer laser, sub-ps pulses produce practically droplet-free films. The absence of droplets has also a beneficial effect on the stoichiometry and homogeneity of the films fabricated by ultrashort pulses.     

Titanium oxide nanostructured films by reactive pulsed laser deposition

Nanostructured titanium oxide thin films have been grown by nanosecond UV pulsed laser deposition (PLD) performed in a reactive background atmosphere. We exploited laser ablation of a Ti target at different pressures of pure oxygen and Ar:O₂ mixtures to show that film growth can be tuned at the nanoscale from compact and dense to columnar and to porous, leading to different morphology, density and structure (oxidized fraction and degree of crystallinity). We observed that the position of the substrate relative to the time integrated visible plume front is fundamental in the determination of film structure and morphology. Film growth and film properties can be related to a non-dimensional parameter L which is the ratio between the target-to-substrate distance and the visible plume length. In particular, surface morphology and degree of structural order are strictly related to L irrespective of the oxygen content, while the latter mainly affects the oxidized fraction in the film.     

Thermal properties of 15-mol% gadolinia doped ceria thin films prepared by pulsed laser ablation

Thermal properties of 15-mol% gadolinia doped ceria thin films (Ce_0.85Gd_0.15 O_1.925) prepared by pulsed laser ablation on silicon substrates in the temperature range 473–973 K are presented. Thermal diffusivities and thermal conductivities were evaluated using photoacoustic spectroscopy. The influence of grain size on thermal properties of the films as a function of deposition temperature is studied. It is observed that the thermal diffusivity and the conductivity of these films decreases up to 873 K and then increases with substrate temperatures. The thermal properties obtained in these films are discussed on the basis of influence of grain size on phonon scattering.     

Hydrogen doping of MgO thin films prepared by pulsed laser deposition

Hydrogen doped MgO films were grown by pulsed laser deposition method. Gaseous hydrogen stored in cavities of milky MgO single crystal targets provided doping in film deposition process. Clear MgO targets without hydrogen were used in the preparation of reference films. The influence of hydrogen doping on firing voltage (FV) of gas discharge and its AC frequency dependence was investigated. According to thermoluminescence experiments, the films grown from milky targets contained two kinds of electron traps with the activation energies of 0.051 and 0.31 eV, while latter traps were absent in reference samples. The 0.31 eV trap was assigned to the hydride ion H⁻ occupying an oxygen vacancy site in MgO crystal structure. Using standard gas mixture (Ne-10% Xe), FVs of hydrogen doped sample showed considerable frequency dependence and were up to 55 V lower in comparison to the reference sample. The FVs of reference sample were shifted 14-28 V to higher values when N₂ gas was added to the mixture. The N₂ addition lowered the FVs of hydrogen doped sample up to 38 V and almost eliminated the FV frequency dependence.     

脉冲高能量密度等离子体法制备TiN薄膜及其摩擦磨损性能研究

利用脉冲高能量密度等离子体技术在室温条件下在45号钢基材上制备出了超硬耐磨TiN薄膜.利用XRD，XPS，AES，SEM等手段分析了薄膜的成分及显微组织结构，并测试了薄膜的硬度分布及摩擦磨损性能.结果表明：薄膜主要组成相为TiN，薄膜组织致密、均匀，与基材之间存在较宽的混合界面；薄膜硬度高，在干滑动磨损实验条件下具有优异的耐磨性及较低的摩擦系数. 关键词： 脉冲高能量密度等离子体 TiN膜 显微组织 耐磨性     

Characterization of polymer thin films obtained by pulsed laser deposition

The development of laser techniques for the deposition of polymer and biomaterial thin films on solid surfaces in a controlled manner has attracted great attention during the last few years. Here we report the deposition of thin polymer films, namely Polyepichlorhydrin by pulsed laser deposition. Polyepichlorhydrin polymer was deposited on flat substrate (i.e. silicon) using an NdYAG laser (266 nm, 5 ns pulse duration and 10 Hz repetition rate).The obtained thin films have been characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry.It was found that for laser fluences up to 1.5 J/cm² the chemical structure of the deposited polyepichlorhydrin polymer thin layers resembles to the native polymer, whilst by increasing the laser fluence above 1.5 J/cm² the polyepichlorohydrin films present deviations from the bulk polymer.Morphological investigations (atomic force microscopy and scanning electron microscopy) reveal continuous polyepichlorhydrin thin films for a relatively narrow range of fluences (1-1.5 J/cm²).The wavelength dependence of the refractive index and extinction coefficient was determined by ellipsometry studies which lead to new insights about the material.The obtained results indicate that pulsed laser deposition method is potentially useful for the fabrication of polymer thin films to be used in applications including electronics, microsensor or bioengineering industries.     

Oxide films of copper prepared by the oxidation of copper sulphide films

Copper sulphide films prepared by reactive evaporation, when heated in air at 500 K, oxidized to Cu₂O after a series of intermediate chemical transitions. Golden yellow coloured Cu₂O films showed a large absorption before the fundamental absorption edge. The optical band gap was found to be (2.29±0.02)eV. When these Cu₂O films were further heated they got converted to CuO and the optical band gap was found to be (2.17±0.02)eV.     

Surface metallization of alumina ceramics by pulsed high energy density plasma process

Surface metallization of alumina ceramics was carried out by pulsed high energy density plasma (PHEDP). A layer of copper film was deposited on the surface of alumina ceramics. Scanning auger electron microscopy (SAM) analysis revealed that copper diffused deep into the alumina substrate. Bonding of alumina and copper film was good. The reaction between copper and alumina was studied by X-ray diffraction (XRD) analysis. A copper aluminum oxide unstable at high temperature and very difficult to be synthesized, cubic phase CuAl₂O₄, was detected. A kinetics complexity in reaction of PHEDP and ceramics was discussed. An adiabatic model was used to describe heating and quenching of the PHEDP processing and analyze the interaction between PHEDP and alumina ceramics. The experimental results suggest that PHEDP method is a useful technology for various metal–ceramics bonding.     

Chemical composition of ZrC thin films grown by pulsed laser deposition

ZrC films were grown on (1 0 0) Si substrates by the pulsed laser deposition (PLD) technique using a KrF excimer laser working at 40 Hz. The nominal substrate temperature during depositions was set at 300 °C and the cooling rate was 5 °C/min. X-ray diffraction investigations showed that films deposited under residual vacuum or under 2 × 10⁻³ Pa of CH₄ atmosphere were crystalline, exhibiting a (2 0 0)-axis texture, while those deposited under 2 × 10⁻² Pa of CH₄ atmosphere were found to be equiaxed and with smaller grain size. The surface elemental composition of as-deposited films, analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), showed the usual high oxygen contamination of carbides. Once the topmost 2-4 nm region was removed, the oxygen concentration rapidly decreased, down to around 3-8% only in bulk. Simulations of the X-ray reflectivity (XRR) curves indicated a smooth surface morphology, with roughness values below 1 nm (rms) and films density values of around 6.30-6.45 g/cm³, very close to the bulk density. The growth rate, estimated from thickness measurements by XRR was around 8.25 nm/min. Nanoindentation results showed for the best quality ZrC films a hardness of 27.6 GPa and a reduced modulus of 228 GPa.     

金属Fe薄膜的PLD制备及其非线性光学性质研究

采用脉冲激光沉积（PLD）技术在MgO基片上制备了金属Fe薄膜.利用原子力显微镜研究了不同制备温度对薄膜表面形貌的影响.x射线衍射分析表明沉积温度大于500℃时，Fe薄膜在MgO基片上有很好的结晶性，并有单一取向.通过z扫描方法测量了超薄Fe膜的光学非线性，得到了Fe薄膜的非线性折射率n₂＝709×10^-5cm²/ kW，非线性吸收系数 β＝-552×10^-3cm/W. 关键词： Fe薄膜 非线性 脉冲激光沉积     

Preparation of nanowall Bi2S3 films by chemical bath deposition

Nanowall shaped Bi₂S₃ films were prepared by chemical bath deposition in which ammonium citrate and thioacetamide were used as chelating reagent and sulfur source, respectively. The nanowall Bi₂S₃ films show large-surface-area nanowall shaped morphology. It is found that the pH value (pH = 6 or pH = 6.5) of the solution is a crucial parameter to obtain the nanowall shaped Bi₂S₃ films. The composition of the nanowall Bi₂S₃ films is close to the stoichiometric ratio of Bi₂S₃. The absorption edge of the nanowall shaped Bi₂S₃ films is located at around 900 nm, indicating that the optical bandgap of the Bi₂S₃ films is around 1.4 eV. The nanowall Bi₂S₃ films show obvious photo-sensitivity. The photo-to-dark conductivity ratios of the nanowall Bi₂S₃ films prepared at pH = 6 and pH = 6.5 are all around 50. This value is around five times than that of the non-nanowall shaped Bi₂S₃ films which is prepared at pH = 7.     

Effect of Er doping on optical band gap energy of TiO2 thin films prepared by spin coating

In order to evaluate the effect of Er doping in the range of 0–1.0 mol% on optical indirect band gap energy (E_g) of the film, the Er-doped TiO₂ (Er-TiO₂) thin films were spin-coated onto fluorine-doped SnO₂ coated (FTO) glasses. Glancing angle X-ray diffraction (GAXRD) results indicated that the films whose thickness was 550 nm consisted of pure anatase and FTO substrate. The anatase (101) TiO₂ peaks became broader and weaker with the rise in Er content. The apparent crystallite size decreased from 12 nm to 10 nm with increasing the amount of Er from 0 mol% to 1.0 mol%. UV–vis spectrophotometry showed that the values of E_g decreased from 3.25 eV to 2.81 eV with the increase of Er doping from 0 to 0.7 mol%, but changed to 2.89 eV when Er content was 1.0 mol%. The reduction in E_g might be attributed to electron and/or hole trapping at the donor and acceptor levels in the TiO₂ band structure.     

Deposition of zinc oxide thin films by reactive pulsed laser ablation

Thin films of zinc oxide have been deposited by reactive pulsed laser ablation of Zn and ZnO targets in presence of a radio frequency (RF) generated oxygen plasma. The gaseous species have been deposited at several substrate temperatures, using the on-axis configuration, on Si (1 0 0). Thin films have been characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and infrared spectroscopy. A comparison among conventional PLD and reactive RF plasma-assisted PLD has been performed.     

Nanocrystalline formation and optical properties of germanium thin films prepared by physical vapor deposition

Amorphous and nanocrystalline germanium thin films were prepared on glass substrates by physical vapor deposition (PVD). The influence of thermal annealing on the characteristics of the Ge thin films has been investigated. X-ray diffraction (XRD) and SEM show amorphous structure of films deposited at room temperature. After thermal annealing, the crystallinity was improved when the annealing temperature increases. The Ge thin films annealed at different temperatures in air were nanocrystalline, having the face-centered cubic structure with preferred orientation along the 〈1 1 1〉 direction. The nanostructural parameters have been evaluated by using a single-order Voigt profile analysis. Moreover, the analysis of the optical transmission and reflection behavior was carried out. The values of direct and indirect band gap energies for amorphous and nanocrystalline phases are 0.86±0.02, 0.65±0.02 and 0.79±0.02, 0.61±0.02 eV, respectively. In addition, the complex optical functions for the wavelength range 600-2200 nm are reported. The refractive index of the nanocrystalline phase drops from 4.80±0.03 to 2.04±0.02, and amorphous phase changes from 5.18±0.03 to 2.42±0.02 for the whole wavelength range. The dielectric functions ε₁ and ε₂ of the deposited films were recorded as a function of wavelength within the range from 600 to 2200 nm.     

脉冲高能量密度等离子体材料表面改性及其应用

脉冲高能量密度等离子体（pulsed high energy density plasma, PHEDP）是一项新的材料表面改性技术.它集高电子温度、高能量密度、高定向速度于一身,在制备薄膜时具有沉积薄膜的温度低、沉积效率高、能量利用率高的优点,并兼具表面溅射、离子注入、冲击波和强淬火效应等综合效应;它可以制备纳米晶或非晶硬质薄膜,提高基底材料的表面硬度和耐磨、耐蚀性能;能够实现非金属材料表面金属化,所制备薄膜与基底之间存在很宽的混合过渡区,因此膜/基结合良好.文章主要介绍了作者近年来在该领域的部分研究成果,简要介绍了脉冲高能量密度等离子体的原理、特点及应用.分析了脉冲等离子体与材料相互作用的基本物理现象.     

Mn doped ZnO nanostructured thin films prepared by ultrasonic spray pyrolysis method

Mn-doped ZnO thin films with different percentage of Mn content (0, 1, 3 and 5 at.%) and substrate temperature of 350 °C, were deposited by a simple ultrasonic spray pyrolysis method under atmospheric pressure. We have studied the structural and optical properties by using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and ultra-violet visible near infrared (UV–Vis-NIR) spectroscopy. The lattice parameters calculated for the Mn-doped ZnO from XRD pattern were found to be slightly larger than those of the undoped ZnO, which indicate substitution of Mn in ZnO lattice. Compared with the Raman spectra for ZnO pure films, the Mn-doping effect on the spectra is revealed by the presence of additional peak around 524 cm⁻¹ due to Mn incorporation. With increasing Mn doping the optical band gap increases indicating the Burstein–Moss effect.     

Role of vanadium content in ZnO thin films grown by pulsed laser deposition

Vanadium-doped ZnO films (Zn_1−xV_xO, where x = 0.02, 0.03, 0.05 and 0.07), were formed from ceramic targets on c-cut sapphire substrates using pulsed laser deposition at substrate temperature of 600 °C and oxygen pressure of 10 Pa. In order to clarify how the vanadium concentration influences the films’ properties, structural and magnetic investigations were performed. All films crystallised in wurtzite phase and presented a c-axis preferred orientation at low concentrations of vanadium. The results implied that the doping concentration and crystalline microstructure influence strongly the system's magnetic characteristics. Weak ferromagnetism was registered for the film with the lowest doping concentration (2 at.%), which exhibited a ferromagnetic behavior at Curie temperature higher than 300 K. Increasing the vanadium content in the film caused degradation of the magnetic ordering.