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首页> 外文期刊>Applied Surface Science >Electron energy loss spectra from polycrystalline Cr and Cr2O3 before and after surface reduction by Ar+ bombardment
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Electron energy loss spectra from polycrystalline Cr and Cr2O3 before and after surface reduction by Ar+ bombardment

机译：Ar +轰击表面还原前后多晶Cr和Cr2O3的电子能量损失谱

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Electron energy loss spectra (ELS) have been obtained from polycrystalline Cr and Cr2O3 before and after surface reduction by 2 keV Ar+ bombardment. The primary electron energy used in the ELS measurements was systematically varied from 100 to 1150 eV in order to distinguish surface versus bulk loss processes. Two predominant loss features in the ELS spectra obtained from Cr metal at 9.0 and 23.0 eV are assigned to the surface and bulk plasmon excitations, respectively, and a number of other features arising from single electron transitions from both the bulk and surface Cr 3d bands to higher-lying states in the conduction band are also present. The ELS spectra obtained from Cr2O3 exhibit features that originate from both interband transitions and charge-transfer transitions between the Cr and O ions as well as the bulk plasmon at 24.4 eV. The ELS feature at 4.0 eV arises from a charge-transfer transition between the oxygen and chromium ions in the two surface layers beneath the chemisorbed oxygen layer, and the ELS feature at 9.8 eV arises from a similar transition involving the chemisorbed oxygen atoms. The intensity of the ELS peak at 9.8 eV decreases after Ar+ sputtering due to the removal of chemisorbed oxygen atoms. Sputtering also increases the number of Cr2+ states on the surface, which in turn increases the intensity of the 4.0 eV feature. Furthermore, the ELS spectra obtained from the sputtered Cr2O3 surface exhibit features characteristic of both Cr-0 and Cr2O3, indicating that Ar+ sputtering reduces Cr2O3. The fact that neither the surface- or the bulk-plasmon features of Cr-0 can be observed in the ELS spectra obtained from sputtered Cr2O3 while the loss features due to Cr-0 interband transitions are clearly present indicates that Cr-0 atoms form small clusters lacking a bulk metallic nature during Ar+ bombardment of Cr2O3. (c) 2005 Elsevier B.V. All rights reserved.
机译：在2keV Ar +轰击表面还原之前和之后，由多晶Cr和Cr2O3获得了电子能量损失谱（ELS）。 ELS测量中使用的一次电子能量从100到1150 eV系统地变化，以区分表面损耗与体积损耗过程。从9.0和23.0 eV的Cr金属获得的ELS光谱中的两个主要损耗特征分别分配给表面和体等离激元激发，以及从体和表面Cr 3d谱带到表面Cr的单电子跃迁到电子跃迁产生的许多其他特征在导带中还存在较高的状态。从Cr2O3获得的ELS光谱表现出的特征既来自Cr和O离子之间的带间跃迁和电荷转移跃迁，也位于24.4 eV的体等离子体激元。在4.0 eV时的ELS特征是由化学吸附的氧层下面的两个表面层中的氧和铬离子之间的电荷转移跃迁引起的，而在9.8 eV时的ELS特征是由涉及化学吸附的氧原子的类似跃迁引起的。在Ar +溅射之后，由于去除了化学吸附的氧原子，ELS峰在9.8 eV处的强度降低。溅射还会增加表面上Cr2 +态的数量，进而增加4.0 eV特征的强度。此外，从溅射的Cr 2 O 3表面获得的ELS光谱显示出Cr-0和Cr 2 O 3的特征，表明Ar +溅射还原了Cr 2 O 3。从溅射的Cr2O3获得的ELS光谱中都没有观察到Cr-0的表面或整体等离激元特征，而由于Cr-0带间跃迁而引起的损耗特征却很明显，这表明Cr-0原子形成很小Cr2O3的Ar +轰击过程中，团簇缺乏整体金属性质。 （c）2005 Elsevier B.V.保留所有权利。

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