A new method of phase-modulated excimer laser crystallization is adopted to fabricate the patterned nanometer-sized crystalline silicon (nc-Si) dots within the sandwiched structure (a-SiNx:H/a-Si:H/a-SiNx:H) films. The results of transmission electron microscopy, electron diffraction and Raman scattering show the ultra-thin and single-layer nc-Si films were patterned in the lateral direction and the size of crystallites is controlled by the thickness of as-deposited a-Si film in the longitudinal direction. The effects of the laser energy density on the structures of the samples and the crystallization mechanism are discussed. 相似文献
We present here the first magnetisation measurements on isolated single crystalline Fe-nanoparticles performed with a ballistic
Hall micro-magnetometer. The measurements have a sensitivity of and thus provide us the possibility to study the mechanisms of magnetisation reversal in a single nanoparticle. The magnetic
properties of the nanoparticles are influenced by their crystal structure and shape, and the presence of an oxide surface
layer. They exhibit curling of the magnetic moments, but also a novel hysteresis behaviour. The spin configurations found
for the system agree well with numerical calculations based on a Heisenberg Hamiltonian including the exchange and dipole
interaction and surface anisotropy.
Received: 1st September 1998 and Received in final form 21 June 1999 相似文献
High quality nanocrystalline diamond film deposited rapidly by an XeCl excimer laser operated at high laser power (500 W) and repetition rate (300~500 Hz) is presented. A high deposition rate, 250 nm/thousand pulses, was obtained. The effects of laser energy fluence and repetition rate on the deposition of diamond film were investigated. 相似文献
Raman scattering of nanocrystalline silicon embedded in SiO2 matrix is systematically investigated. It is found that the Raman spectra can be well fitted by 5 Lorentzian lines in the Raman shift range of 100-600 cm-1. The two-phonon scattering is also observed in the range of 600-1100 cm-1. The experimental results indicate that the silicon crystallites in the films consist of nanocrystalline phase and amorphous phase; both can contribute to the Raman scattering. Besides the red-shift of the first order optical phonon modes with the decreasing size of silicon nanocrystallites, we have also found an enhancement effect on the second order Raman scattering, and the size effect on their Raman shift. 相似文献
Scanning tunneling microscopy (STM) and spectroscopy (STS) have been used to determine the structural and electronic properties
of thiol-passivated 29000 amu gold nanocrystals, both individually and in spontaneously formed quasi-two-dimensional arrays.
Experiments were performed at temperatures of 300 K, 77 K, and 8 K. Even at room temperature, tunneling through these 1.7
nm nanocrystals is shown to give rise to a Coulomb blockade. At cryogenic temperatures, the spectroscopy of the nanocrystals
in arrays and in isolation shows an incremental charging effect (the Coulomb staircase) and evidence is found for quantization
of the electronic states.
Received: 10 September 1998 / Received in final form: 16 February 1999 相似文献
Third harmonic generation from planar and spherical metal surfaces is studied theoretically through the standard Green function
method, so that the results are not affected by the uncertainty associated with previous simplified models. In general the
pattern of the non-linear scattering loosely resembles the pattern of Mie scattering. The strong backward scattering is uniquely
related to the non-linear process. These results differ significantly from the predictions of the surface charge model.
Received: 20 May 1998 / Received in final form: 25 August 1998 / Accepted: 1st September 1998 相似文献
The ground-state geometries, energetics and the stability of
(n=1-12) clusters are studied using ab initio molecular dynamics method. Our results indicate that the ground-state geometries of large clusters () are different from those of clusters where a trivalent impurity Al is added to the same monovalent host Na. Other features observed are an early appearance
of 3-dimensional structure and a pentagonal growth path from n=6 up to n=11. As expected, the ground-state geometry of is not an icosahedron but can be viewed as a distorted form of one of the low lying geometries of cluster. In the energetically favored structures impurity atom Mg is never located at the center of the cluster. The stability
analysis based on the energetics shows (8 valence electrons) to be the most stable. In addition there is a remarkable even-odd pattern observed in the dissociation
energy and the second difference in energy which is absent in earlier studies of and clusters.
Received: 16 September 1998 / Received in final form: 15 February 1999 相似文献
Summary: Blends of poly(9,9‐dioctylfluorene) (PFO) and poly(2‐methoxy‐5(2′‐ethyl‐hexyloxy)‐1,4‐phenylenevinylene) (MEH‐PPV) were found to phase separate into 40–50 nm crystalline PFO domains and to exhibit efficient white electroluminescence when the composition is below 30 wt.‐% MEH‐PPV. The 5 wt.‐% nanocrystalline blends had a luminance of 4 000 cd · m−2, an external quantum efficiency of 3.1%, and a current efficiency of 3.7 cd · A−1. Transmission electron microscopy, electron diffraction, and atomic force microscopy of blends with higher MEH‐PPV content and the two homopolymers showed them to be amorphous. Only orange‐red electroluminescence, characteristic of MEH‐PPV, was observed from the amorphous blends due to efficient energy transfer from PFO. These results demonstrate that energy transfer processes in binary PFO:MEH‐PPV blends and light‐emitting devices based on them can be controlled through the morphology and composition.