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排序方式: 共有331条查询结果,搜索用时 15 毫秒
21.
R.M. Freeman F. Haas M.-P. Nicoli A. Morsad Z. Basrak 《The European Physical Journal A - Hadrons and Nuclei》1999,4(3):239-244
It has been noticed that a distinct resemblance exists at large angles among angular distributions measured for reaction
channels at the energies of some resonance-like structures in the 12C+12C and 14C+16O systems. It is pointed out that such forms are typical of a diffraction pattern of a broad band of coherent partial waves.
Received: 5 October 1998 / Revised version: 8 December 1998 相似文献
22.
Silicon suboxide thin films have been fabricated by physical vapor deposition of silicon monoxide in vacuum at controlled
oxygen partial pressure. These films undergo a phase separation into silicon- and oxygen-enriched regions upon thermal processing.
At temperatures around 900 °C, the onset of Si nanocrystallite formation is observed, regardless of film stoichiometry. With
increasing initial oxygen content of the films, the mean size of created nanocrystallites decreases whereas the corresponding
photoluminescence emission blueshifts. The photoluminescence intensity increases with increasing annealing temperature up
to 1050 °C. Upon resonant excitation at low temperatures, the photoluminescence exhibits phonon replica signature. Therefore,
the emission may be attributed to excitonic recombination in the nanocrystallites.
Received: 3 July 2001 / Accepted: 6 August 2001 / Published online: 17 October 2001 相似文献
23.
Ph. Ebert 《Applied Physics A: Materials Science & Processing》2002,75(1):101-112
This work reports the measurement of the nano-scale physical properties of surface vacancies and the extraction of the types
and concentrations of dopant atoms and point defects inside compound semiconductors, primarily by cross-sectional scanning
tunneling microscopy on cleavage surfaces of III–V semiconductors. The results provide the basis to determine the physical
mechanisms governing the interactions, the formation, the electronic properties, and the compensation effects of surface as
well as bulk point defects and dopant atoms.
Received: 10 May 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献
24.
The adsorption of L-alanine on Cu(111) surface is studied by means of scanning tunnelling microscopy under ultra-high vacuum conditions. The results show that the adsorbates are chemisorbed on the surface, and can form a two-dimensional gas phase, chain phase and solid phase, depending on deposition rate and amount. The adsorbed molecules can be imaged as individual protrusions and parallel chains in gas and chain phases respectively. It is also found that alanine can form (2 × 2) superstructure on Cu(111) and copper step facet to (110) directions in solid phase. On the basis of our scanning tunnelling microscopic images, a model is proposed for the Cu(111)(2 ×2)-alanine superstructure. In the model, we point out the close link between (110)-direction hydrogen bond chains with the same direction copper step faceting. 相似文献
25.
The presence of parts per million (ppm) levels of impurities in the low-temperature arsenic charge used in molecular beam epitaxy (MBE) is shown to have a dramatic effect on the quality of GaAs grown. Source charge impurities play a vital role in determining the apparent variation in reported doping behaviour in MBE:GaAs. 相似文献
26.
Xiaonan Sun 《Applied Surface Science》2010,256(7):2228-2231
The formation of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) nanostrutures on Au(1 1 1)-() covered with NaCl islands has been studied using scanning tunneling microscopy (STM). Atomically resolved STM images show that NaCl grows as (1 0 0)-terminated layers on Au(1 1 1)-(). Local atomic hexagonal packing has also been observed in the NaCl(1 0 0) layer. At submonolayer NaCl coverage, PTCDA forms two-dimensional islands on the Au(1 1 1) surface and nucleate preferentially at the NaCl island step edges. When the Au surface is fully covered with NaCl layers, PTCDA molecules form three-dimensional molecular clusters decorating the step edges of NaCl layers. 相似文献
27.
Chao Song Jun Xu Guran Chen Yu Liu Ling Xu Kunji Chen 《Applied Surface Science》2010,257(4):1337-1341
Intrinsic, P- and B-doped hydrogenated amorphous silicon thin films were prepared by plasma-enhanced chemical vapor deposition technique. As-deposited samples were thermally annealed at the temperature of 800 °C to obtain the doped nanocrystalline silicon (nc-Si) films. The microstructures, optical and electronic properties have been evaluated for the undoped and doped nanocrystalline films. X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of the substitutional boron and phosphorous in the doped films. It was found that thermal annealing can efficiently activate the dopants in films accompanying with formation of nc-Si grains. Based on the temperature-dependent conductivity measurements, it was shown that the activation of dopant by annealing increased the room temperature dark conductivity from 3.4 × 10−4 S cm−1 to 5.3 S cm−1 for the P-doped films and from 1.28 × 10−3 S cm−1 to 130 S cm−1 for the B-doped films. Meanwhile, the corresponding value of conductivity activation energies was decreased from 0.29 eV to 0.03 eV for the P-doped films and from 0.3 eV to 5.6 × 10−5 eV for the B-doped films, which indicated the doped nc-Si films with high conductivity can be achieved with the present approach. 相似文献
28.
Y. Safa D. Pfenniger 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):337-352
The equation of state and the stability of the helium-molecular hydrogen mixture at cryogenic temperature up to moderate pressure
are studied by means of current molecular physics methods and statistical mechanics perturbation theory. The phase separation,
segregation and hetero-coordination are investigated by calculating the Gibbs energy depending on the mixture composition,
pressure and temperature. Low temperature quantum effects are incorporated via cumulant approximations of the Wigner-Kirkwood
expansion. The interaction between He and H2 is determined by Double Yukawa potentials. The equation of state is derived from the hard sphere system by using the scaled
particle theory. The behavior of the mixture over a wide range of pressure is explored with the excess Gibbs energy of mixing
and the concentration fluctuations in the long wavelength limit. The theory is compared to cryogenic data and Monte-Carlo
calculation predictions. Contrary to previous similar works, the present theory retrieves the main features of the mixture
below 50 K, such as the critical point and the condensation-freezing curve, and is found to be usable well below 50 K. However,
the method does not distinguish the liquid from the solid phase. The binary mixture is found to be unstable against species
separation at low temperature and low pressure corresponding to very cold interstellar medium conditions, essentially because
H2 alone condenses at very low pressure and temperature, contrary to helium. 相似文献
29.
A. Grabowski N. Kruszewska R. A. Kosiński 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):107-113
We study properties of five different social systems: (i) internet society of friends consisting of over 106 people, (ii) social network consisting of 3 × 104 individuals, who interact in a large virtual world of Massive Multiplayer Online Role Playing Games (MMORPGs), (iii) over
106 users of music community website, (iv) over 5 × 106 users of gamers community server and (v) over 0.25 × 106 users of books admirer website. Individuals included in large social network form an Internet community and organize themselves
in groups of different sizes. The destiny of those systems, as well as the method of creating of new connections, are different,
however we found that the properties of these networks are very similar.
We have found that the network components size distribution follow the power-law scaling form. In all five systems we have
found interesting scaling laws concerning human dynamics. Our research has shown how long people are interested in a single
task, how much time they devote to it and how fast they are making friends. It is surprising that the time evolution of an
individual connectivity is very similar in each system. 相似文献
30.
A simple method for estimating shape functions of optical spectra is proposed, based on the numerical correlation with an assumed optical spectrum composed of a central main rectangular component and two right-angled triangular wings on either side of the main component. The degrees of correlation between observed and assumed spectra were examined using spectral and coherence widths of those spectra and pulsewidths of Fourier-transform-limited pulses calculated from those spectra. By using this method, shape functions of output spectra from superluminescent diodes and a self-pulsating laser diode were evaluated in detail over a relatively wide injection current range beyond their rated currents. 相似文献