Atomic-Scale Modification of Oxidation Phenomena on the Ge(100) Surface by Si Alloying

Properties of Ge oxides are significantly different from those of widely used Si oxides. For example, the instability of GeOx at device junctions causes electronic defect levels that degrade the performance of Ge-containing devices (e.g., transistors and infrared detectors). Therefore, the passivating Si layers have been commonly used at Ge interfaces to reduce the effects of Ge oxide instability and mimic the successful strategy of Si oxidation. To contribute to the atomic-scale knowledge and control of oxidation of such Si-alloyed Ge interfaces (O/Si/Ge), we present a synchrotron radiation core-level study of O/Si/Ge, which is combined with scanning probe microscopy measurements. The oxidation processes and electronic properties of O/Si/Ge(100) are examined as functions of Si amount and oxidation doses. In particular, the incorporation of Si into Ge is shown to cause the strengthening of Ge−O bonds and the increase of incorporated oxygen amount in oxide/Ge junctions, supporting that the method is useful to decrease the defect-level densities.</p

The role of the collecting duct in urinary concentration

The various segments of the collecting duct have interesting and important roles in the urinary concentrating mechanism. On one hand, the collecting duct contributes insignificantly to the medullary interstitial concentrating process, but on the other hand, urinary concentration occurs as the result of water abstraction from the collecting duct as it courses from the cortex to the papillary tip. Thus, the collecting duct seems to do little work for medullary concentration. It, nevertheless, gets credit for regulation of the final urine osmolality. The latter occurs as a consequence of finely tuned mechanisms which regulate the collecting duct's water permeability in an ambience where the interstitial osmolality is controlled by highly integrated mechanisms involving numerous different nephron segments. The purpose of this article is to review the specific role of each segment of the collecting duct in the urinary concentrating mechanism, while other contributions in this Symposium will discuss the water permeability of the collecting duct and the generation and maintenance of the medullary interstitial osmolality