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291.
We present different relaxation mechanisms of Ge and SiGe quantum dots under excimer laser annealing. Investigation of the coarsening and relaxation of the dots shows that the strain in Ge dots on Ge films is relaxed by dislocation since there is no interface between the Ge dots and the Ge layer, while the SiGe dots on Si0.77Ge0.23 film relax by lattice distortion to coherent dots, which results from the obvious interface between the SiGe dots and the Si0.77Ge0.23 film. The results are suggested and sustained by Vanderbilt and Wickham's theory, and also demonstrate that no bulk diffusion occurs during the excimer laser annealing. 相似文献
292.
I. Ruiz de Larramendi R. López-Antón J. I. Ruiz de Larramendi T. Rojo 《Applied Physics A: Materials Science & Processing》2008,93(3):655-661
Polycrystalline samples of Pr1−x
Sr
x
Fe0.8Co0.2 O3−δ
(x=0.1, 0.2, 0.3) (PSFC) were prepared by the combustion synthesis route at 1200°C. The structure of the polycrystalline powders
was analysed with X-ray powder diffraction data. The X-ray diffraction (XRD) patterns were indexed as the orthoferrite similar
to that of PrFeO3 having a single-phase orthorhombic perovskite structure (Pbnm). Pr1−x
Sr
x
Fe0.8Co0.2O3−δ
(x=0.1, 0.2, 0.3) films have been deposited on yttria-stabilized zirconia (YSZ) single-crystal substrates at 700°C by pulsed
laser deposition (PLD) for application to thin film solid oxide fuel cell cathodes. The structure of the films was analysed
by XRD, scanning electron microscopy (SEM) and atomic force microscopy (AFM). All films are polycrystalline with a marked
texture and present pyramidal grains in the surface with different size distributions. Electrochemical impedance spectroscopy
(EIS) measurements of PSFC/YSZ single crystal/PSFC test cells were conducted. The Pr0.7Sr0.3Fe0.8Co0.2O3−δ
film at 850°C presents a lower area specific resistance (ASR) value, 1.65 Ω cm2, followed by the Pr0.8Sr0.2Fe0.8Co0.2O3−δ
(2.29 Ω cm2 at 850°C) and the Pr0.9Sr0.1Fe0.8Co0.2O3−δ
films (5.45 Ω cm2 at 850°C). 相似文献
293.
M. Aoki K. Miwa T. Noritake N. Ohba M. Matsumoto H.-W. Li Y. Nakamori S. Towata S. Orimo 《Applied Physics A: Materials Science & Processing》2008,92(3):601-605
We have investigated the structural and dehydriding properties of Ca(BH4)2. It was found that Ca(BH4)2 undergoes a structural phase transformation from an orthorhombic low-temperature (LT) modification into a tetragonal high-temperature
(HT) modification between 433 K and 523 K. The amount of hydrogen desorbed from Ca(BH4)2 during the pressure–composition (p–c) isotherm measurement was 5.9 mass%. This hydrogen desorption is caused by the partial dehydrogenation of Ca(BH4)2 accompanied by the formation of CaH2 and orthorhombic intermediate phases. 相似文献
294.
TEM,XRD and AFM study of poly(<Emphasis Type="Italic">o</Emphasis>-ethoxyaniline) films: new evidence for the formation of conducting islands 总被引:1,自引:0,他引:1
Fabio L. Leite William F. Alves Mirta Mir Yvonne P. Mascarenhas Paulo S. P. Herrmann Luiz H. C. Mattoso Osvaldo N. OliveiraJr. 《Applied Physics A: Materials Science & Processing》2008,93(2):537-542
The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly(o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH=3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasi-one dimensional variable range hopping (VRH) mechanism. 相似文献
295.
Physical properties of a nanocrystalline thin film is greatly influenced by its morphological and structural evolution. We try to understand the transition of SnO2 thin films from amorphous to nanocrystalline structure with XRD, IR, SEM, AFM and surface profiler studies. A 2D layer like structure resulting from quantum confinement is found for the films prepared at 400 °C. We observed a new IR band at 530 cm−1 that was theoretically predicted and report it for the first time. A correlation of population of defects in SnO2 films with change in lattice parameters and FWHM of IR bands are reported. The electric and optical properties of the films have been discussed. 相似文献
296.
The effect of the surface characteristics of Ni catalyst films on the growth behavior of multi-walled carbon nanotubes (MWCNTs) were investigated using Ni catalyst films prepared by different physical vapor deposition methods, electron-beam evaporation and sputtering. The growth behavior of MWCNTs was dependent upon the surface roughness of the Ni films. After a pretreatment process with NH3, the root mean squares of surface roughness of e-beam evaporated and sputtered Ni catalyst films increased to 16.6 and 3.2 nm, respectively. Curled-MWCNTs and carbon-encapsulated Ni nanoparticles were formed on the Ni film deposited by e-beam evaporation while vertically aligned-MWCNTs were grown on the sputter-deposited film. In addition, the surface roughness of the Ni films affected the field emission properties of the MWCNTs. This was considered to originate from the specific growth behavior of the MWCNTs which was primarily caused by the initial surface roughness of the Ni films. 相似文献
297.
Amorphous thin films of TiO2 are irradiated by swift heavy ion (SHI) beam. Surface topography is studied by atomic force microscopy (AFM). Formation of nanosized oblate hillocks on the surface of irradiated films is investigated by AFM studies. After irradiation, amorphous to crystalline phase transition is observed in glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy studies. Photoluminescence (PL)-spectroscopy is carried out for optical characterization. Threshold value necessary for emergence of hillocks is estimated. 相似文献
298.
C2H4 mediations were used to modify the Stranski-Krastanow growth mode of Ge dots on Si(0 0 1) at 550 °C by ultra-high vacuum chemical vapor deposition. With appropriate C2H4-mediation to modify the Si surface, the elongated Ge hut clusters can be transformed to highly uniform Ge domes with a high Ge composition at the core. These C2H4-mediated Ge dots, almost bounded by {1 1 3} facets, have an average diameter and height of 55 and 9 nm, respectively. We propose two major mechanisms to depict the formation of these C2H4-mediated Ge dots: (i) an almost hydrogen-passivated Si surface to limit the nucleation sites for dot formation, and (ii) the incorporation of Ge atoms, repelled by the C-rich areas, into the existing Ge dots. This work provides a useful scheme to tune the topography of Ge dots in an UHV/CVD condition for possible optoelectronic applications. 相似文献
299.
The poly(propylene imine) dendrimer DAB-dendr- (NH2)8 was hydrophobically modified with dodecanoyl end groups. The modified dendrimer was deposited onto mica by adsorption from solution and observed by atomic force microscopy. With the decrease of adsorption time, the modified dendrimer varied from continuous film to scattered islands. For the adsorption time of 20s the dendrimer formed a sub-monolayer thin film that contained many fractal aggregates of fractal dimension 1.80 that were > 1 microm in diameter and no more than 0.8nm thick. After 5 months at 1#1 , the initial fractal aggregates transformed into disks and other less-branched shapes with average heights of the domains of 0.6nm and 0.4nm, respectively. Formation of the fractal aggregates is explained by diffusion-limited aggregation. The slow reorganization of dendrimer molecules in the fractal aggregates occurs at a temperature well above the Tg of the dendrimer. 相似文献