利用俄歇-γ符合谱确定铜基石墨烯低能电子发射的俄歇机制
Identification of Auger mechanisms responsible for low energy electron emission from graphene on copper using Auger-gamma coincidence spectroscopy
摘要：
我们提出了一种新的方法来分析的多普勒展宽的γ光子发射后的湮没表面捕获的正电子与电子的双层石墨烯支撑在多晶铜衬底。该方法依赖于多普勒频移湮没伽马光子的能量的测量，该能量与同时产生的湮没诱导空穴衰变后发射的俄歇电子一致。通过选择对应于O KVV（吸附O），C KVV（石墨烯）和Cu MVV（衬底）俄歇跃迁的湮没γ，我们将湮没γ谱分解为表示正电子与C和O的1s电子和Cu的3p电子的湮没的谱分量。这些实验得出的多普勒加宽的伽马线形状与理论推导的模型线形状吻合良好，证明了我们的方法能够将复杂的多普勒线形状解析成其隐蔽的电子能级成分，这在此之前只能通过理论分析来实现。我们还证明了通过将俄歇谱分解成对应于具有大多普勒频移的湮没伽马光子或与具有小多普勒频移的湮没伽马光子相关的俄歇谱的区域的分析方法的可逆性。反向分析提供了额外的证据，俄歇跃迁后的深价湮灭导致低能电子的发射。
英文摘要：
We present a novel method for the analysis of the Doppler broadened spectrum of gamma photons emitted following the annihilation of surface trapped positrons with the electrons of bilayer graphene supported on polycrystalline Cu substrate. The method relies on the measurement of the energy of the Doppler shifted annihilation gamma photons in coincidence with the Auger electrons emitted following the decay of the contemporaneously produced annihilation induced hole. Through the selection of annihilation gamma corresponding to O KVV (adsorbed O), C KVV (graphene), and Cu MVV (substrate) Auger transitions, we have decomposed the annihilation gamma spectrum into spectral components representing annihilation of the positron with 1s electrons of C and O and 3p electrons of Cu. These experimentally derived Doppler broadened gamma line shapes agrees well with the theoretically derived model line shapes demonstrating the ability of our method to resolve a complex Doppler line shapes into its veiled electronic level constituents which has, heretofore, only been achieved through theoretical analysis. We have also demonstrated the reversibility of the analysis method by decomposing the Auger spectra into regions which corresponds to the annihilation gamma photons with a large Doppler shift or to Auger spectra correlated with annihilation gamma photons with a small doppler shift. The reverse analysis provides additional proof that Auger transitions following deep valence annihilations result in the emission of low energy electrons.
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