溅射超薄Au膜表面形貌的分形表征

采用直流磁控溅射技术制备超薄Au膜,用原子力显微镜观察薄膜的表面形貌。功率谱密度计算结果显示,随着溅射时间增加,高频段曲线拟合直线的斜率增大,相应的分形维数从2.579减小到2.500;而低频段曲线拟合直线的斜率减小,相应的分形维数由2.607增大到2.819,薄膜表面形貌存在多尺度行为。多重分形谱结果表明,随着溅射时间的增加,分形谱宽Δα从0.051增大到0.118,说明薄膜表面高度分布范围愈来愈宽,表面粗糙度愈来愈大,与rms研究结果一致。样品的Δf均0,说明样品表面最高峰位的数目均多于最低谷位的数目。     

Effects of surface topography on magnetization reversal of magnetic thin films

The influence of the created surface roughness on the coercivity of magnetic thin films has been investigated. The magnetic thin films (CoFe and alternatively NiFe) are sputtered on top of smooth substrates that were previously covered with an array of considerably rougher lines with one of these materials Pt, Cu, CoFe, and NiFe. The lines have been patterned using optical lithography into arrays that are deposited with different thicknesses varying between 5 nm-15 nm. The lines have been designed to have a very rough edge and seated in two different angles relative to the wafer edge (zero and 45 degrees). Magneto-optic Kerr effect (MOKE) measurements showed two distinct switching fields in the hysteresis loops that are due to magnetic domain wall trapping created by the surface roughness. The magnetization reversal showed a strong dependence on the height, the orientation angle, and the material's type of the created surface roughness (the lines).     

Morphology, surface topography and optical studies on electron beam evaporated MgO thin films

Electron beam evaporated thin films of MgO powder synthesized by burning of magnesium ribbon in air and sol-gel technique are studied for their microstructure (SEM), surface topography (AFM), and optical transmission behaviour (UV-visible spectroscopy). MgO thin films are shown to be either continuous or have mesh like morphology. The bar regions are believed to be of magnesium hydroxide formed due to absorption of moisture. Their AFM images exhibit columnar/pyramidal/truncated cone structure, providing support to the 3D Stranski-Krastanov model for film growth. Further, they are shown to have high transmittance (∼90%) in the wavelength range 400–600 nm, but absorb radiation below 350 nm substantially giving signature of a band transition.     

Study of surface topography and optical properties of Ge15Bi38Se47 films

Adherent and smooth amorphous GeBiSe films deposited by vacuum evaporation at substrate temperatures less than 30 °C have been studied for their structural and optical properties. The films were crystallized by thermal annealing and they were found to be polycrystalline in nature. A correlation between X-ray diffraction (XRD) data and surface topography is reported. Optical constants calculated from reflectance and transmittance data indicate semiconducting behaviour. The optical band gap of the as-deposited film is 1.0 eV. The measured optical contrast at 0.8 m is 44%. No significant changes in the optical parameters have been observed after exposing the samples to laboratory ambient for a period of six months. © 1998 Chapman & Hall     

Growth and surface morphology of uranium films during molecular plating

Molecular plating is a widely used technique for the preparation of lanthanide and actinide targets. We have studied the growth and surface morphology of uranium films during the molecular plating process using atomic force microscopy, scanning electron microscopy, Raman and IR spectroscopy and X-ray fluorescence. During deposition of U films on 10 μm Al backings by molecular plating, the RMS roughness increased from 17 to 446 nm for deposition times up to 45 min and then decreased to 223 nm for deposition times of 120 min, which gave the smoothest films with a fractal dimension of 2.10.     

Laser desorption from the surface of copper phthalocyanine films on silicon and cadmium sulfide

We have studied laser desorption mass spectra of copper phthalocyanine (CuPc) films deposited in vacuum onto single crystal silicon and cadmium sulfide substrates. The desorption was induced by 10-ns pulses of neodymium laser radiation (quantum energy, 2.34 eV) with an energy density E varied from 0.1 to 40 mJ/cm². It is established that laser radiation produces fragmentation of CuPc molecules and desorption of the fragments. The main fragments observed in the mass spectra are identified. The intensity of the main desorbed species has been studied as a function of the laser pulse energy density. The components of CdS substrates penetrate into the volume of deposited CuPc films in the form of Cd atoms and S₂ molecules.     

Enhanced adhesion of osteoblastic cells on polystyrene films by independent control of surface topography and wettability

We independently controlled surface topography and wettability of polystyrene (PS) films by CF₄ and oxygen plasma treatments, respectively, to evaluate the adhesion and proliferation of human fetal osteoblastic (hFOB) cells on the films. Among the CF₄ plasma-treated PS films with the average surface roughness ranging from 0.9 to 70 nm, the highest adhesion of hFOB cells was observed on a PS film with roughness of ~ 11 nm. When this film was additionally treated by oxygen plasma to provide a hydrophilic surface with a contact angle less than 10°, the proliferation of bone-forming cell was further enhanced. Thus, the plasma-based independent modification of PS film into an optimum nanotexture for human osteoblast cells could be appplied to materials used in bone tissue engineering.     

Growth and surface characterization of magnetron sputtered zinc nitride thin films

Zinc nitride films were deposited on Si(100) substrates at room temperature using RF-magnetron sputtering in pure N₂ and in Ar + N₂ atmospheres. Two active phonon modes (270.81 and 569.80 cm^− 1) are observed in Raman spectra for films deposited in Ar + N₂ atmosphere. Atomic force microscopy showed that the average surface roughness of the films deposited in pure N₂ atmosphere (1.3-3.33 nm) was less than for those deposited in a mixed Ar + N₂ atmosphere (10.3-12.8 nm). Low temperature cathodoluminescence showed two emission bands centered at 2.05 eV and 3.32 eV for both types of films.     

Electronic and adsorption properties of the real surface of cadmium selenide films containing indium whiskers

An investigation is made to determine how surface doping of thin semiconducting cadmium selenide films with heavy metal atoms influences their binding energy and their absorption sensitivity to oxygen. Under certain doping conditions, indium atom whiskers are formed on the surface of the films. These samples show an appreciable reduction in the oxygen binding energy with the surface and a reversible response in the interaction with oxygen at 353 K. Pis’ma Zh. Tekh. Fiz. 23, 13–17 (August 12, 1997)     

Influence of SHI irradiation on the structure and surface topography of CdTe thin films on flexible substrate

Impact of ion irradiation on thin films is an emerging area for materials modification. CdTe thin films grown by thermal evaporation on flexible molybdenum (Mo) substrate were irradiated with Swift (100 MeV) Ag⁺⁷ ions for various ion fluence in the range 10¹²–10¹³ ions/cm². The modifications in the composition, structure and surface morphology have been studied as a function of ion fluence. The Energy Dispersive X-ray Analysis (EDS) shows slightly Te-rich composition for both as-grown and irradiated films with no significant change after irradiation. X-ray diffraction (XRD) analysis indicates a consistent shift in the (111) peak position towards higher diffraction angle and an increase in the full width at half maximum (FWHM) with increase in ion fluence. The change in the residual stress during irradiation has been evaluated and is related to the corresponding microstructural changes in the films. The initial tensile stress is found to be relaxed after irradiation. Atomic Force Microscopy (AFM) studies revealed significant grain splitting after irradiation and formation of hillocks at higher ion fluence. The surface roughness was significantly increased at higher ion fluence.     

Effects of high hydrogen dilution ratio on surface topography and mechanical properties of hydrogenated nanocrystalline silicon thin films

Hydrogenated nanocrystalline silicon thin films were deposited with high hydrogen dilution ratio by plasma enhanced chemical vapor deposition technique. The effects of high hydrogen dilution on the surface topography and mechanical properties of the films were studied with atomic force microscopy and TriboIndenter nano indenter. The results indicate that the average grain size in films deposited with high hydrogen dilution is about 3.18 ± 0.02 nm. The surface roughness and densification of the films decrease with the increase of hydrogen dilution ratio at certain range, resulting in the enhancement of the elastic modulus E and hardness H. Oppositely, the increase of hydrogen dilution can increase the surface roughness induced by the increase of the cavities on the film surfaces, and lead to the decrease of the elastic modulus and hardness correspondingly. In this paper, the detailed analysis and discussion were carried out to investigate the mechanism of the observed phenomena.     

Luminescence and photoconductivity of alkali-metal-doped cadmium sulfide films

Data are presented on the luminescence and photosensitivity of cadmium sulfide films doped with an alkali metal (Na or K) in the presence of chlorine. The doping is shown to increase the luminescence quantum yield by more than one order of magnitude in comparison with undoped CdS films. The doped films are resistant to high-intensity UV radiation, which usually initiates photochemical reactions.     

The surface topography of retrieved femoral heads

Excessive wear of UHMWPE sockets is considered detrimental to the long-term performance of total hip replacement procedures. Although many factors contribute to the wear process, laboratory experiments have indicated that one of the most important factors affecting the wear rate is surface topography and in particular, the arithmetic mean surface roughness, R _a, of the hard counterface. Surface roughness values were therefore obtained from the heads of 37 explanted and five new Charnley prostheses. The surface topography was measured using a Rodenstock RM 600 non-contacting profilometer. Five parameters were used to give a quantitative characterization of the surface texture; arithmetic mean surface roughness, R _a, root mean square (RMS) surface roughness, R _q, peak to valley height, R _t, average single peak to valley height from five adjoining sample lengths, R _z, and the skewness of the height distribution, Sk. Further, qualitative investigations were undertaken using a Joel-JSM-IC848 scanning electron microscope (SEM). The median values of R _a, R _q, R _t and R _z for explanted heads showed statistically significant increases when compared with values from new prostheses. No significant difference was found between any of these parameters measured in the anterior-posterior and the medial-lateral directions. This result may have important implications for the design of joint simulators. No correlation was found between any of the parameters and implant period.     

Trap diagnostic of thin cadmium sulphide films

A simplified expression for the temperature dependence of trap depth was derived. This expression together with experimental observations confirmed the existence of a number of deep trap levels (0.9–1.02 eV) in CdS and it is suggested that with the knowledge of these trap levels a better correlation between experimental and theoretical results for tunnel-induced impact ionization is possible.