Microscopic study of the surfactant‐assisted Si, Ge epitaxial growth
The Sb‐assisted Si, Ge epitaxial growth processes have been studied using high resolution photoemission. It is found that the initially ordered Sb monolayer on the Si(100) and Ge(100) surfaces occupies the epitaxial sites and fully saturates the surface dangling bonds. This results in a reduction of the surface energy. During the growth process, the Sb atoms and the deposited Si, Ge atoms change their positions. Sb atoms segregate to the growth front to form a new ordered layer while leaving the uniform epitaxial Si, Ge layer behind.
Kinetics of pulsed ultraviolet laser induced oxidation of c‐Ge: The role of optical coupling and material losses
Ultraviolet pulsed laser induced oxidation kinetics of crystalline germanium (c‐Ge) is determined from real‐time optical measurements in conjunction with absolute measurements of the oxygen incorporation performed by nuclear reaction analysis. Although the oxidation process can be triggered at laser fluences initially below the melting threshold of c‐Ge, it is strongly activated when surface melting occurs and therefore the fast oxidation process observed is mainly a thermally activated process. Because an optical coupling between the oxide layer and the c‐Ge underneath, the growth kinetics is complex and leads to nonconstant rates. The oxygen incorporation reaches a saturation value which depends both on the laser fluence and the oxygen pressure. The results show that the oxygen incorporation is limited by an overlapped laser‐induced material removal process rather than by the diffusion length of oxygen species.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.