SiGe-on-insulator substrate fabricated by melt solidification for a strained-silicon complementary metal-oxide-semiconductor J.Effects of H + implantation ͑ഛ5 ϫ 10 16 cm −2 ͒ on stress relaxation in an oxidation-induced Ge condensation method have been investigated to form stress-relaxed ultrathin ͑ϳ30 nm͒ SiGe-on-insulator ͑SGOI͒ virtual substrates. High-dose ͑ജ10 15 cm −2 ͒ implantation enhanced stress relaxation, which was attributed to bond breaking at the SiGe/ buried SiO 2 interface. However, oxidation velocity was also enhanced due to irradiation defects. Two-step annealing ͑500°C for 30 min and 850°C for 60 min͒ before oxidation was proposed to remove irradiation defects. This achieved enhanced stress relaxation in ultrathin SGOI without changing oxidation velocity.
Strain-relaxation process of SiGe-on-insulator (SGOI) structures in the oxidation induced Ge condensation method has been investigated as a function of the SiGe thickness. Complete relaxation was obtained for thick SGOI layers (>100nm). However, the relaxation rates abruptly decreased with decreasing SiGe thickness below 50nm, i.e., the relaxation rate of 30% at 30nm SiGe thickness. In order to improve this phenomenon, a method combined with H+ irradiation with a medium dose (5×1015cm−2) and postannealing (1200°C) has been developed. This successfully achieved the high relaxation rate (70%) in the ultrathin SGOI (30nm).
A necessary and sufficient condition for flatness of the quasi-spherical spacetimes of Szekeres is given. Using this, the linear approximation of these space-times is considered and it is shown that the third derivatives of the quadrupole moments vanish for matter distribution contained within a comoving surface. Hence the Einstein formula gives zero energy loss due to gravitational radiation. This agrees with other investigations, which have shown that no radiation is present in these space-times.
We consider the polarization of unstable type-IIB D0-branes in the presence of a background five-form field strength. This phenomenon is studied from the point of view of the leading terms in the non-abelian Born Infeld action of the unstable D0-branes. The equations have SO(4) invariant solutions describing a non-commutative 3-sphere, which becomes a classical 3-sphere in the large-N limit. We discuss the interpretation of these solutions as spherical D3-branes. The tachyon plays a tantalizingly geometrical role in relating the fuzzy S 3 geometry to that of a fuzzy S 4 .
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