Study of cuprous oxide using time of flight positron annihilation induced Auger electron spectroscopy

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 (M 2,3 VV) Auger peak as the sample is subjected to thermal anneal in the vacuum at 300 0 C temperature for 13 minutes. Exposure of the vacuum annealed surface to oxygen resulted in a large reduction of Cu (M 2,3 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.

Direct evidence for low-energy electron emission following O LVV Auger transitions at oxide surfaces

“…The increased low-energy intensity for oxygen on Cu and Si, and the broad, low-energy peak in TiO 2 are each associated with the presence of oxygen on the surface, as indicated by the O KVV Auger peaks. Additionally, the Cu and Si core Auger peak intensities decreased due to the oxygen-induced displacement of the positron wave function away from the Cu and Si atoms of the surface [14][15][16][17][18] . In the TiO 2 , the relatively small Ti M 2,3 VV Auger signal relative to the two oxygen-derived Auger signals is consistent with previous findings that the positron wave function overlap for TiO 2 is primarily with the surface oxygen atoms 19,20 .…”

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

“…These results indicate that the intensity of the Cu M 2,3 VV Auger peak for the oxidized Cu(100) surface is reduced by ~93% compared to the clean surface. Experimental annihilation probability, p nl , of positrons trapped at the oxidized Cu(100) surface with Cu 3p core electrons estimated from the measured Cu M 2,3 VV Auger peak intensity shows a significant decrease when compared to its value obtained from the clean Cu(100) surface [5,6] This paper presents the results of theoretical studies of positron surface and bulk states and annihilation characteristics of surface trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. Such studies are indispensable for full interpretation of PAES data.…”

“…Unlike conventional Auger techniques that average over several atomic layers, positron annihilation induced Auger electron spectroscopy (PAES) has a very high degree of top layer selectivity due to the fact that the positrons are trapped just outside the surface prior to annihilation, hence is ideal to probe the near surface region [4]. Recently this technique has been applied to study the oxidized Cu(100) single crystal [5,6]. The PAES spectrum from the clean Cu(100) surface is shown in figure 1 (a).…”