Structure of Amorphous Fe_<80>-P_<13>-C_7 by X-Ray Diffraction

X-ray diffraction patterns have been obtained from Fe_-P_-C_7 alloy in both amorphous and liquid states. Using the common Fourier analysis, the atomic radial distribution function was evaluated from which interatomic distance and coordination number were obtained. The essential feature of the structure in the amorphous state was similar to that in the liquid state. The crystallization process of this alloy during isothermal aging at 330℃ was also studied by the same procedures. The results indicated that the initial amorphous structure changes to a second amorphous structure, which in turn, transforms to the stable crystalline phase. This crystallization product was single phase of bcc structure (a_0=2.864A). By means of the Fourier analysis, these results led to the conclusion that the initial amorphous structure re-arranges to relax the stress or anisotropic configuration of atoms arising from the rapid quenching and subsequently the crystallization of this alloy occurs by a nucleation and growth mechanism during isothermal aging

Structural Study of an Amorphous Pd_<80>-Si_<20> Alloy by X-Ray Fourier Analysis

The structure of an amorphous Pd_-Si_ alloy obtained by rapid quenching from the liquid state has been studied by X-ray diffraction . After calculating the interference function by means of the Fourier analysis, the atomic radial distribution function is obtained from which interatomic distance and coordination number are estimated. Comparing the result with that in the liquid state it is found that the general feature of the structure in the amorphous state is quite similar to that in the liquid state. Besides, the sample aged at 180℃ for 300 min is examined by the same procedures

Influence of carrier-carrier and carrier-phonon correlations on optical absorption and gain in quantum-dot systems

A microscopic theory is used to study the optical properties of semiconductor quantum dots. The dephasing of a coherent excitation and line-shifts of the interband transitions due to carrier-carrier Coulomb interaction and carrier-phonon interaction are determined from a quantum kinetic treatment of correlation processes. We investigate the density dependence of both mechanisms and clarify the importance of various dephasing channels involving the localized and delocalized states of the system.Comment: 12 pages, 10 figure

Structural Study of an Amorphous Bi-Fe-Ca-O Thin Film by the Anomalous X-ray Scattering

The structure of the amorphous Bi-Fe-Ca-O film with 0.3 m thick grown on the Si single crystal was studied by the anomalous x-ray scattering (AXS) method. This relatively new method using the anomalous dispersion effect of a specific constituent element in a film reduces the difficulty in the subtraction process of a substrate intensity for estimating the net intensity of a thin film, which becomes a main cause of errors of the resultant data in the conventional method. The environmental radial distribution functions around Bi and Fe in the amorphous Bi-Fe-Ca-O film were determined, from which the structural features were obtained

Exact-Diagonalization Studies of Inelastic Light Scattering in Self-Assembled Quantum Dots

We report exact diagonalization studies of inelastic light scattering in few-electron quantum dots under the strong confinement regime characteristic of self-assembled dots. We apply the orthodox (second-order) theory for scattering due to electronic excitations, leaving for the future the consideration of higher-order effects in the formalism (phonons, for example), which seem relevant in the theoretical description of available experiments. Our numerical results stress the dominance of monopole peaks in Raman spectra and the breakdown of selection rules in open-shell dots. The dependence of these spectra on the number of electrons in the dot and the incident photon energy is explicitly shown. Qualitative comparisons are made with recent experimental results.Comment: 11 pages, 11 figure