PACS. 81.15.Hi -Molecular, atomic, ion, and chemical beam epitaxy. PACS. 68.65.-k -Low-dimensional, mesoscopic, and nanoscale systems: structure and nonelectronic properties. PACS. 78.67.Lt -Quantum wires.Abstract. -An original mechanism is described for the self-assembly of nanometer-sized structures in the silicon germanium material system. The self-organized formation of vertical Si-rich quantum wells (VSQW) is obtained during the growth of Si1−xGex on narrow line-shaped Si mesa, which are oriented in 150 on the Si (001) surface. The occurrence of the VSQW is accompanied by the formation of {15 3 23} facets on top of the mesa. Detailed structural insights have been gathered by cross-sectional transmission electron microscopy, secondary electron microscopy and photoluminescence measurements. Ge quantum wires are embedded into the VSQW forming a superlattice containing SiGe and Ge wires. Intense low-temperature photoluminescence, which can be assigned to this one-dimensional superlattice, has been observed.

No abstract

Gate dielectrics formed by N2O oxynitridation using a rapid thermal annealer (RTA) and a furnace were developed and evaluated. The oxynitrides formed by RTA show very large time‐to‐breakdown ( Tnormalbd ) values and small stress‐induced leakage current, as compared with pure oxides and oxynitrides formed by furnace annealing. The depth profile of the Nlnormals peak for oxynitfides was analyzed by X‐ray photoelectron spectroscopy. Nitrogen atoms in the oxynitrides formed by RTA are localized at the normalSi/SiO2 interface. and those in the oxynitrides formed during furnace annealing exist uniformly throughout the film. The differences in nitrogen bond state in the oxynitride between the RTA and the furnace are due to the decomposition of N2O gas. A nitrogen atom at the normalSi/SiO2 interface bonds with one oxygen and two silicon atoms false(Si2=N‒Ofalse) , or bonds with three silicon atoms false(Si3≡Nfalse) . A nitrogen atom located in the bulk of the film, however, bonds with two oxygen atoms and one silicon atom false(normalSi‒N=O2false) . We clarified that the electrical and chemical characteristics of the oxynitride depend on the location of N2O gas decomposition. Thus, precise control of the nitrogen profile and the nitrogen bond states is very important for the formation of highly reliable N2O oxynitride. © 2000 The Electrochemical Society. All rights reserved.

An explosive volcanic eruption occurred in the Ogasawara Islands on 13–15 August 2021, bringing unprecedented amounts of floating pumice to the coast of Okinawa Island in the Ryukyu Archipelago, 1300 km west of the volcano, approximately 2 months later. The coast of Okinawa Island, especially along the northern part, is home to many typical subtropical seascapes, including coral reefs and mangrove forests, so the possible impact of the large amount of pumice is attracting attention. Here, we report early evidence of ecosystem changes as a result of large-scale pumice stranding on coastal beaches, in estuaries and mangrove forests and passage across fringing coral reefs. Massive pumice drifts are major obstacles to fishing activities and ship traffic, but short and long-term changes in coastal ecosystems can also occur. The phenomena observed on Okinawa Island can be a preview of coastal impacts for the Kyushu, Shikoku, Honshu Islands, where pumice has subsequently washed ashore.

No abstract