Atomic arrangement at the 3C-SiC/Si(001) interface revealed utilising aberration-corrected transmission electron microscope

The atomistic structure of the 3C-SiC/Si(001) interface has been investigated using a combination of aberration-corrected transmission electron microscopy and a newly developed image processing method for eliminating artificial contrast. The structures having periods four times longer than those of the silicon lattice have been observed distinctly in images taken along both Si[110] and Si[100] directions. Contrary to theoretical models proposed previously, the interface of the three-dimensional structural model that we constructed on the basis of our experiments has a silicon-rich configuration. We have clarified that the strain field induced by the two-dimensional misfit between Si(001)-(4?×?4) and SiC(001)-(5?×?5) is relaxed by the two-dimensional network of misfit dislocations; simple edge dislocations with [100] and [010] directions and Lomer dislocations with [110] and [110] directions. The atomistic structures of the Lomer dislocations have been also clarified.     

Cascade effects on the irradiation stability of amorphous SiOC

We studied the heavy ion radiation tolerance of amorphous silicon oxycarbide (SiOC) alloys by in situ Kr ion irradiation within a transmission electron microscopy. The amorphous SiOC thin films were grown via co-sputtering from SiO₂ and SiC targets on a surface-oxidized Si (100) substrate. These films were irradiated by 1 MeV Kr ions at both room temperature and 300 °C with damage levels up to 5 displacements per atom (dpa). TEM characterization shows no sign of crystallization, void formation or segregation in all irradiated samples. Our findings suggest that SiOC alloys are a class of promising radiation tolerant materials.     

Kinetics of the persistent photocurrent in semiconductors: a case example for amorphous chalcogenides

Although the persistent photocurrent or the residual photocurrent decay (RPD) in photoconductive semiconductors is known to be dominated by dispersive recombination kinetics which produce the stretched exponential functional decay, exp(-Ct^β), where β (<1.0) is the dispersion parameter, the reason for the occurrence of the RPD is still not clear. We discuss the origin of the dispersive nature of long-term photocurrent decay in amorphous chalcogenides (a-Chs) as a case example. The slow recombination path of excess photocarriers in a-Chs can be attributed to their characteristic feature of negative-U defects at which lattice relaxation with multiphonon process may play a role.     

On the Symbiosis of Science and Religion: A Jewish Perspective

Three theses are explored, the first two historical and the third philosophical-theological: (1) throughout most of the history ofWestern civilization, science and religion have been closely connected with each other, and each has benefited from the connection; (2) the belief that science and religion have always been in conflict is not based on the actual history of either set of institutions; and (3) structurally a relationship between the two institutions is in the interest of both. By religion here I mean specifically, but not exclusively, Judaism.     

Dislocation motion in silicon: the shuffle-glide controversy revisited

Considering recently computed formation and migration energies of kinks on nondissociated dislocations, we have compared the relative mobilities of glide partial and shuffle perfect dislocations in silicon. We found that the latter should be more mobile over all the available stress range, invalidating the model of a stress driven transition between shuffle and glide dislocations. We discuss several hypotheses that may explain the experimental observations.     

Quantitative prediction of phase transformations in silicon during nanoindentation

This paper establishes the first quantitative relationship between the phases transformed in silicon and the shape characteristics of nanoindentation curves. Based on an integrated analysis using TEM and unit cell properties of phases, the volumes of the phases emerged in a nanoindentation are formulated as a function of pop-out size and depth of nanoindentation impression. This simple formula enables a fast, accurate and quantitative prediction of the phases in a nanoindentation cycle, which has been impossible before.     

The Origins of Life: What One Needs to Know

Many solar systems in the universe may be expected to contain rocky planets that have accreted organic compounds. These compounds are likely to be universally found. In addition, the chemistry of sulfur, phosphorus, and iron is likely to dominate energy transductions and monomer activation, leading to the eventual emergence of polymers. Proteins and polynucleotides provide living matter with function, structure, and information. The conceptual puzzle regarding their emergence is discussed. The fitness of various elements to serve various roles is analyzed from the viewpoint of electron orbitals. Elements with d orbitals are of central importance.     

Microstructure and phase evolution in spark-plasma-sintered Al86Ni6Y4.5Co2La1.5 glassy alloy

Al₈₆Ni₆Y_4.5Co₂La_1.5 amorphous powders synthesized after 200 h of mechanical alloying were spark plasma sintered at 25 and 400 MPa at 400 °C for 15 min. The sample sintered at 25 MPa showed precipitation of FCC-Al grains of sub-micron size attributed to a higher amount of localized high-temperature regions which favoured faster long-range atomic diffusion. On the contrary, the 400-MPa sintered sample showed the presence of nanocrystals (5–20 nm) distributed in an amorphous matrix. This is attributed to higher pressure sintering favouring local and short-range atomic redistributions. The higher amount of retained amorphous phase in the 400-MPa sintered sample could be accounted for by a smaller amount of localized high-temperature regions in comparison to those in 25-MPa sintered sample. High-pressure sintering induces shear fracturing and fragmentation of the brittle amorphous particles and provided better surface contact and packing density. The retention of a larger amount of amorphous phase and a higher relative density (96%) contributes to high microhardness (278 Hv) and nanoindentation hardness (3.7 GPa) of the 400-MPa sintered sample.