The morphology and growth process of oxide precipitates in Czochralski silicon have been studied with prolonged thermal treatments up to 700 h at intermediate temperatures (700–900 °C). It was found with transmission electron microscopy observation that (i) the morphology of precipitates changes from platelet to aggregation of polyhedra at both 800 and 900 °C during isothermal heat treatment, and (ii) the growth of platelet precipitates follows a t1/2 law.

A new experimental set-up was developed to evaluate the strain dependence of critical current (I c (ε a )) for YBa 2 Cu 3 O 7−δ (YBCO)-coated conductors under a magnetic field in a variable temperature environment. In this paper, we report the first results on the effect of a magnetic field parallel to the c axis (B c) on I c (ε a ) up to 10 T at temperatures of 60-77 K. We found that the magnetic field affects I c (ε a ) in a different manner, depending on the field region. When the magnetic field increases from B = 0 T, normalized I c (ε a ) is first improved and the optimal situation is realized under the characteristic magnetic field of B p = 0.2 T at 77 K and B p = 0.4 T at 70 K, respectively. For higher magnetic field, I c (ε a ) degrades further with increasing strain. From the results of a fitting analysis, we confirmed that the strain at the peak of I c (ε a ) shifts to higher strain and reaches the maximum value at B p . The peak shift as a function of magnetic field found in the YBCO-coated conductors is in contrast with the I c (ε a ) behavior for conventional low temperature superconducting composites, in which all of the critical parameters are optimized when the intrinsic strain of the superconductor is zero. From the present result, we can conclude that the peak strain of the I c (ε a ) curve under a magnetic field is not determined only by the thermal residual strain of the YBCO film in the coated conductor. For the high field region, the curvature of the I c (ε a ) curve increases with increasing magnetic field and temperature. It results in a steep decrease in I c (ε a ) at high magnetic fields and temperatures.

There is a strong interest to use germanium as an active device layer in deep sub-micron devices. This imposes similar stringent material and process requirements for germanium as for silicon. Lattice defect formation during crystal growth and device processing as well as dopant diffusion and activation are to a large extent controlled by the intrinsic point defects in the semiconductor. The properties of the vacancy and the self-interstitial in germanium are, however, not well known. The scarce available experimental data are combined with ab initio and molecular-dynamics calculations and other published simulation results. Based on this a best estimate is made for the formation and migration energies of the vacancy and the self-interstitial in germanium.

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Density functional theory (DFT) calculations are performed to obtain the formation energies of the vacancy V and the self-interstitial I at all sites within a sphere around the dopant atom with 6 Å radius for V and 5 Å radius for I in Si crystals. Substitutional p-type (B and Ga), neutral (C, Ge, and Sn), and n-type (P, As, Sb, and Bi) dopants were considered. The results show that the formation energies of V and I around dopant atoms change depending on the types and sizes of the dopants, i.e., depending on the electrical state and the local strain around the dopants. The dependence of the total thermal equilibrium concentrations of point defects (sum of free V or I and V or I around the dopants) at melting temperature on the type and concentration of each dopant is obtained. Further DFT calculations reveal that most of the total incorporated point defects from the melt contribute to pair recombination. An appropriate model of point defect behavior in heavily doped single crystal Si growing from a melt is proposed on the basis of DFT calculations. (1) The incorporated total V and I concentrations at melting point depend on the types and concentrations of dopants. (2) Most of the total V and I concentrations during Si crystal growth contribute to the pair recombination at temperatures much higher than those to form grown-in defects. The Voronkov model successfully explains all reported experimental results on intrinsic point defect behavior dependence on dopant type and concentration for heavily doped Si while taking the present model into consideration.