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《Journal of Non》2006,352(9-20):950-954
The evolution of surface roughness on hydrogenated amorphous silicon (a-Si:H) films prepared by plasma-enhanced chemical vapor deposition exhibits initial smoothening due to nuclei coalescence, a region of surface stability, and finally a prominent roughening transition (designated a  a) at a critical thickness. The thickness at which the a  a transition occurs, as measured by real time spectroscopic ellipsometry (SE), is found to correlate closely with the electronic properties of the film. Thus, the transition has been incorporated into deposition phase diagrams that have been applied successfully to optimize solar cell performance and stability. A simple continuum model for the evolution of the 1D surface profile using an initial condition designed to be consistent with the nucleation characteristics measured by real time SE is sufficient for insights into the correlation between the roughness evolution and film properties. Good agreement between the experimental results and model calculations support the concept that optimum electronic properties of the films are associated with weakly reactive surfaces and long lifetime radicals that lead to adsorbed precursors with large surface diffusion lengths.  相似文献   
3.
It is only byneglecting self-adsorption (a treatment referred to as “pure-energy,” PE) that one gets textbook thermodynamics of a surface, based upon the tensionL as a function of temperatureT, and one finds negative specific heat for hot water. Any lower critical point and PE provides the other exciting negatives: nicotine-and-water is an example. In order toinclude adsorption,L must be known in terms ofT and chemical potentials asindependent variables; this forces measurement of the tension of curved menisci. Will the minus signs remain?  相似文献   
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《Journal of Non》2006,352(9-20):1028-1031
The paper reports on thermally stimulated conductivity studies used for characterization of the density of states profile in thin film semiconductors, by numerically solving the non-linear time-dependent rate equations for free and trapped charge. We explore the derivation of energy and density scales from temperature and conductivity data. We examine the distinction between ‘strong’ and ‘weak’ re-trapping and the use of low ‘effective’ values of attempt-to-escape frequencies in establishing an energy scale, and the ad hoc inclusion of a temperature-dependent lifetime. It is confirmed for several illustrative model systems that the technique can afford surprisingly good fidelity in recovery of the density of states under a range of conditions.  相似文献   
5.
We present all-atom molecular dynamics simulations ofn-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules are observed to attain the perpendicular orientation at monolayer coverage. Dedicated to Professor C N R Rao on his 70th birthday  相似文献   
6.
《Journal of Non》2007,353(32-40):3342-3347
The crystallization of the as-quenched Fe76Mo8Cu1B15 ribbon proceeds in four independent transformation steps, which however mutually overlap both in the temperature and time scales. A complex thermokinetic method is presented, by which the individual transformations could be experimentally separated and characterized. The kinetics and mechanism of the individual transformations have been determined. Both linear-heating and isothermal differential scanning calorimetry was used. As-prepared as well as heat-treated samples were characterized by transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy.  相似文献   
7.
《Journal of Non》2007,353(16-17):1515-1520
A theoretical study of stress-impedance effect based on the solution of Landau–Lifsitz–Gilbert equation has been carried out. The results show that stress impedance effects depend largely on several extrinsic (external bias field, external frequency) and intrinsic (orientation and magnitude of uniaxial anisotropy, damping) parameters.  相似文献   
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Electrohydrodynamic instability in homeotropically oriented nematic samples of 4'-n-octyl-4-cyano-biphenyl and 4'n-alkyloxy-4-cyanobiphenyl, (n = 8.9) have been studied in an a.c. electric field. The domain patterns during the instability in these compounds in a very low frequency a.c. field are very similar to those in a d.c. field. The domain patterns observed at higher frequencies have been identified as 'maltese crosses' or 'crossed isogyres'. The electro-convective 'isotropic' flows near the electrode play an important role in the observed instability.  相似文献   
10.
The temperature dependence of the extended X-ray absorption fine structure (EXAFS) is studied in the high Tc superconductors, YBa2Cu3O7−δ. The measurements were done at the Cu K-edge for samples of two orthorhombic phases (Tc≈90 K and ≈58 K, respectively) and a nonsuperconducting tetragonal phase. Interatomic distances and mean square relative displacements σ2 for Cu-O bonds are determined by the least squares refinement. The results indicate that values of σ2 increase near Tc for both the orthorhombic samples. It is concluded that this anomalous behavior related to Tc is caused by an anomalous vibration of oxygen atoms in the Ba-O layer. Changes in the Cu-O distances from 300 to 20 K are not found.  相似文献   
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