The characteristics of intrinsic electron and hole trapping in crystalline and amorphous Al2O3 have been studied using density functional theory (DFT). Special attention was paid to enforcing the piece-wise linearity of the total energy with respect to electron number through the use of a range separated, hybrid functional PBE0-TC-LRC (Guidon et al 2009 J. Chem. Theory Comput. 5 3010) in order ...

– Despite the fact that polymer crystallization has been the object of intense research, this process is far from being fully understood. Traditional polymer crystallization studies using X-ray scattering techniques mainly provide information about the ordered regions. To obtain a more complete information about the time evolution of both the crystalline and the amorphous phase during polymer c...

Amorphous and crystalline phases of Ge2Sb2Te5 films are investigated by coherent phonon spectroscopy. By heating amorphous films above specific temperatures, the coherent phonon signatures exhibit pronounced changes due to the crystallization of the amorphous phase into a cubic lattice and the transition from the cubic to a hexagonal crystal structure. The phonon modes observed are identified b...

By means of normal-incidence, high-flux and high-energy X-rays, total scattering data for pair distribution function (PDF) analysis have been obtained from thin films (tf), suitable for local structure analysis. By using amorphous substrates as support for the films, the standard Rapid Acquisition PDF setup can be applied and the scattering signal from the film can be isolated from the total sc...

Ion tracks formed in amorphous Ge by swift heavy-ion irradiation have been identified with experiment and modeling to yield unambiguous evidence of tracks in an amorphous semiconductor. Their underdense core and overdense shell result from quenched-in radially outward material flow. Following a solid-to-liquid phase transformation, the volume contraction necessary to accommodate the high-densit...

A microscopic model for the resistance drift in the phase-change memory is proposed based on the firstprinciples results on the compressed amorphous Ge2Sb2Te5. First, it is shown that the residual pressure in the phase-change memory cell can be significant due to the density change accompanying the phase transformation. Our previous first-principles calculations showed that the energy gap is re...

Phase-change materials undergo rapid and reversible crystalline-to-amorphous structural transformation and are being used for nonvolatile memory devices. However, the transformation mechanism remains poorly understood. We have studied the effect of electrical pulses on the crystalline-to-amorphous phase change in a single-crystalline Ge(2)Sb(2)Te(5) (GST) nanowire memory device by in situ trans...

We report on measurements of the incoherent elastic neutron-scattering intensity Iel(Q) of polyethylenes with degrees of crystallinity 0.46 and 0.96 in a wide Q ~length of scattering vector! range from 0.4 to 6.2 Å to observe the deviation from the Gaussian behavior. The non-Gaussian behavior was observed in both the amorphous and the crystalline phases. The non-Gaussian behavior in the theoret...

The question of the local stability of the ~replica-symmetric! amorphous solid state is addressed for a class of systems undergoing a continuous liquid to amorphous-solid phase transition driven by the effect of random constraints. The Hessian matrix, associated with infinitesimal fluctuations around the stationary point corresponding to the amorphous solid state, is obtained. The eigenvalues o...

Preliminary results are reported of the amorphization of Nb-Sn and Nb-Ge alloys by mechanical alloying of the elemental powders. Nb-25 at.% Sn, Nb-25 at.% Ge, and Nb-27 at.% Ge alloys were made amorphous. Differential scanning calorimetry (DSC) indicated a crystallization peak at 995 K for Nb-25 at.% Sn but > 1000 K for the Nb-Ge amorphous alloys. A large endothermic DSC peak and the diffractio...