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41.
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. 相似文献
42.
The oxide films formed on AISI 304L stainless steel at 300 °C in the oxidation time range between 2 and 4 h have been studied by photoelectrochemistry. Photocurrents were investigated as a function of the wavelength of the incident light and the electrode potential. The investigation allowed the determination of the semiconductive properties of the oxides. The oxide films showed n-type behaviour. A duplex structure of the oxide films has been suggested on the basis of the photocurrent spectra, with an internal oxide layer having an optical gap (Eg2 = 2.16-2.3 eV) depending on the applied potential and oxidation time, higher to that of the external oxide layer (Eg1 ≈ 1.9 eV). Significant variations in the amplitude of the photocurrent were detected as a function of the applied potential and the oxidation time. 相似文献
43.
We report spectroscopic characterization of epitaxial YBCO thin films grown on LaAlO3 by pulsed laser deposition. Raman spectroscopy and spectroscopic ellipsometry were used for film characterization and the results were correlated with X-ray diffraction measurements. The mentioned techniques allowed us to analyze crystallographic, micro-structural, and morphological properties of YBCO thin films. We also demonstrated that relatively low resolution Raman spectroscopy and spectroscopic ellipsometry are reliable techniques for a rapid and non-destructive characterization of epitaxial YBCO thin films. 相似文献
44.
K. Franke 《Surface science》2005,585(3):144-154
Polarization switching in scanning force microscopy (SFM) is influenced by both electric fields and stress, whereby the latter can arise inherently from Maxwell stress. We discuss the influence of electric charges and of the polarization asymmetry on the switching behaviour. For single crystallites of PZT(53/47) thin films, the sectors for ferroelectric, ferroelastoelectric and ferroelastic switching are represented in a field-stress map. The influence of stress on the second harmonic of the SFM is also discussed. 相似文献
45.
Photoinduced optical and second-order non-linear optical effects in the interfaces separating In2O3–SiON (O/N ratio equals 1) films doped with A1, Sn and glass substrates were investigated using the photoinduced optical second harmonic generation. The photoinduced effective second-order optical susceptibility deff (at λ=1.76 μm) shows a good correlation with the linear optical susceptibility, particularly with the shift of the absorption edge. The maximal response of the photoinduced optical response signal was observed for the pump–probe delaying time of 34 ps. The performed experimental measurements indicate that the observed effects are mainly caused by the interface potential gradients on the border glass–In2O3–SiON film and by additional polarization due to insertion of the Al and Sn atoms. The observed phenomenon may be proposed as a sensitive tool for investigation of thin semiconducting interfacial layers and simultaneously such films may be used as materials for non-linear optical devices. 相似文献
46.
D. Behera T. Mohanty S. K. Dash T. Banerjee D. Kanjilal N. C. Mishra 《Radiation measurements》2003,36(1-6):125-129
Swift heavy ions (SHI) with electronic energy loss exceeding a value of 14.4 keVnm−1 create amorphized latent tracks in YBCO type superconductors. In the low fluence regime of an ion beam where tracks do not overlap, a decrease of the superconducting transition temperature as probed through resistivity studies, is not expected due to availability of percolating current paths. The present study however shows Tc decrease by about 1–3 K in thin films of YBCO when irradiated by 250 MeVAg ions at 79 K at a fluence of 5×1010–1×1012 ionscm−2. The highest fluence used in the present study is three times less than the fluence where track overlapping becomes significant. The Tc tends to increase towards the preirradiation value on annealing the films at room temperature. To explain this unusual result, we consider the effect of ion irradiation in inducing materials modification not only through creation of amorphized latent tracks along the ion path, but also through creation of atomic disorder in the oxygen sublattice in the Cu–O chains of YBCO by the secondary electrons. These electrons are emitted radially from the tracks during the passage of the SHI. Considering the correlation between the charge state of copper and its oxygen coordination, we show in particular that the latter process is a consequence of the inelastic interaction of the SHI induced low-energy secondary electrons with the YBCO lattice, which result in chain oxygen disorder and Tc decrease. 相似文献
47.
在超高真空分子束外延(MBE)生长技术中,反射式高能电子衍射仪(RHEED)能实时显示半导体和金属外延生长过程,给出薄膜表面结构和平整度的信息,成为MBE必备的原位表面分 析仪.为了研究氧化物薄膜如高温超导(YBa2Cu3O7) 、铁电薄膜(Sr1-xBax TiO3)及它们的同质和异质外延结构的生长机理,获得高质量的符合各种应用 需要的氧化 物多层薄膜结构,在常规的制备氧化
关键词:
高温超导薄膜
RHEED 相似文献
49.
N. Nishi J. Nishijo K. Judai C. Okabe O. Oishi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):287-290
UV photoexcitation of (t-butylethynyl copper)24
cluster films induces segregation of the crystals into metallic and organic
phases and leads to evolve the metallic sheets sandwiched by organic
polymers. The growth of the metallic crystals in the plane of the
photo-electromagnetic field is attributed due to plasmon-plasmon interaction
among nanoparticles embedded in dielectric polymer matrices. The surface
enhanced photochemical reaction of residual cluster molecules on the photon
incident direction is expected to take an important role for joining the
metal particles to produce a metallic sheet. We can apply this phenomenon
for photolithographic copper pattern generation on a flexible base plate. 相似文献
50.
The electron-stimulated desorption (ESD) of D− and H− ions from condensed D2O and H2O films is investigated. Three low-energy peaks are observed in the ESD anion yield, which are identified as arising from excitation of 2B1, 2A1 and 2B2 dissociative electron attachment (DEA) resonances. Additional structure is observed between 18 and 32 eV, which may be due to ion pair formation or to DEA resonances involving the 2a1 orbital. The ion yield resulting from excitation of the 2B1 resonance increases as the film is heated. We attribute the increase in the ion yield to thermally induced hydrogen bond breaking near the surface, which enhances the lifetimes of the excited states that lead to desorption. 相似文献