Selective trapping of positrons by Ag nanolayers in a V/Ag multilayer system

N Qi,Z Q Chen,H X Zhang,A Uedono,B Zhao,M Jiang,F Ren

doi:10.1063/1.5143379

Abstract

V/Ag nano-scaled multilayers were prepared by using a magnetron sputtering deposition method. Each layer of Ag and V has a thickness of about 6 nm, and the total thickness of the multilayer film is 350 nm. Doppler broadening of annihilation radiation was measured by using a slow positron beam to study the microstructure of the above samples. It was found that the Doppler broadening S and W parameters measured in the V/Ag multilayers were close to those measured in the Ag reference sample. Coincidence Doppler broadening measurements also showed that the electron momentum distributions in V/Ag multilayers and Ag monolayer were almost identical. This suggests that Ag has a strong affinity to positrons, and almost all the positrons ejected into the multilayers are confined to the Ag nanolayers. Theoretical calculations indicate that the positron wavefunction is well localized in the Ag nanolayer even for a layer thickness of only 1 nm.

Highlights

Nuclear energy has become more and more important in the energy constituents of the future world
The Transmission electron microscopy (TEM) image confirms the formation of multilayer structures with sharp interfaces
The microstructure of V/Ag multilayers was studied by positron annihilation spectroscopy using a slow positron beam

Summary

Introduction

Nuclear energy has become more and more important in the energy constituents of the future world. From the above analysis of the S–E curve for pure Ag layer, one can find that with increasing positron energy, the positrons can detect the surface, Ag layer, and Si substrate, successively. We do believe that the S parameter in the energy range of 0.1–7 keV corresponds to the positron annihilation in the V layer.

Results

Conclusion