Showing papers by "Alex H. Weiss published in 2007"
TL;DR: This study demonstrated the order-of-magnitude enhancement in the PAES to the topmost surface layer in Cu2O relative to the EAES counterpart; factors underlying this contrast are discussed and the implications of ultrathin carbon layers on semiconductor surfaces are discussed.
Abstract: Vacuum anneal induced changes in the surface layers of electrodeposited copper(I) oxide (Cu2O) were probed by time-of-flight positron annihilation induced Auger electron spectroscopy (TOF-PAES) and by electron induced Auger electron spectroscopy (EAES). Large changes in the intensity of the Cu PAES intensity resulting from isochronal in situ vacuum anneals made at increasing temperatures indicated that, before thermal treatment, the surface was completely covered by a carbonaceous overlayer and that this layer was removed, starting at a temperature between 100 and 200 °C, to expose an increasing amount of Cu in the top layer as the anneal temperature was increased. The thickness of this overlayer was estimated to be ∼4 A based on analysis of the EAES data, and its variation with the thermal anneal temperature was mapped. This study demonstrated the order-of-magnitude enhancement in the sensitivity of PAES to the topmost surface layer in Cu2O relative to the EAES counterpart; factors underlying this contra...
12 citations
TL;DR: The annihilation of positrons with core electrons results in an element specific signature in the spectra of Auger-electron and annihilation gamma rays, which can be used for future applications of AGCS and gamma-gamma coincidence spectroscopy as discussed by the authors.
5 citations
TL;DR: In this article, a model of the energy spectra of individual steps of the Mn L23→M2,3M2.3M 2.3→M 2,3m2, 3.3m 2.5m→M1,3n 2.2m 2m2m 3.1m2.
3 citations
TL;DR: In this article, a positron annihilation induced Auger electron spectroscopy (PAES) was used to study the surface changes in the surface of copper oxide after vacuum annealing and reoxidation.
Abstract: Changes in the surface of copper (I) oxide resulting from vacuum annealing and reoxidation after vacuum annealing have been investigated using positron annihilation induced Auger electron spectroscopy (PAES). The PAES measurement shows a large monotonic increase in the intensity of the annihilation induced Cu (M2,3 VV) Auger peak as the sample is subjected to thermal anneal in the vacuum at 300 °C temperature for 13 minutes. Exposure of the vacuum annealed surface to oxygen resulted in a large reduction of Cu (M2,3 VV) intensity and an increase in the signal due to the KLL transition in O. These results provide a clear demonstration of the utility of PAES in the study of oxide surfaces. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
3 citations
01 Aug 2007-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions, which reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered.
Abstract: Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M 4,5 N 1 N 2,3 , M 2,3 M 4,5 M 4,5 , M 2,3 M 4,5 V and M 1 M 4,5 M 4,5 Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 × 1), Ge(1 0 0)-p(2 × 2) and Ge(1 0 0)-c(4 × 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered.