Oxygen-dosage effect on the structure and composition of ultrathin NiO layers reactively grown on Ag(001)
Oxygen-dosage effect on the structure and composition of ultrathin NiO layers reactively grown on Ag(001)
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DOI：
10.1103/physrevb.69.075418
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发表时间：
2004-02
影响因子：
3.7
通讯作者：
C. Giovanardi;A. D. Bona;S. Valeri
中科院分区：
文献类型：
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作者：
C. Giovanardi;A. D. Bona;S. Valeri
在超高真空条件下，采用金属沉积法在Ag（0 0 1）衬底上制备了NiO薄膜.通过沉积对应于1 ML（单层）的NiO在不同的氧气与金属的流量比的存在下，金属的量来制备的薄膜，以研究氧气的剂量对生长层的结构和组成的影响和对化学计量的Ni氧化物。还制备了更厚的膜（高达20 ML）。该结构已被监测在相互和直接空间的低能电子衍射和初级束衍射调制的电子发射。核心水平的X射线光电子能谱已被用来研究薄膜的化学和成分。在低覆盖率（低于2 ML）的结构和组成上的氧-镍通量比的显着依赖性已被观察到。低氧剂量引起1-ML膜中的（2×1）重构，该重构随着氧剂量和/或膜厚度的增加而演变为（1×1）相。在低氧剂量下制备的层中，大部分金属Ni与Ni氧化物共存，但氧化部分在很大程度上占主导地位的高氧剂量。生长过程中的氧剂量也影响较厚的膜。马赛克的形成，这已被归因于失配应变松弛，是一个低的氧镍通量比。
NiO ultrathin films have been prepared under UHV conditions on Ag(001) substrate by metal deposition in O 2 atmosphere. The films were prepared by deposition of the amount of metal correspondent to 1 ML (monolayer) of NiOin the presence of different oxygen-to-metal flux ratios, to investigate the oxygen dosage effect on the structure and composition of the growing layer and on the stoichiometry of Ni oxide. Thicker films (up to 20 ML) were also prepared. The structure has been monitored both in reciprocal and direct space by low-energy electron diffraction and primary-beam diffraction-modulated electron emission. Core-level x-ray photoemission spectroscopy has been used to study film chemistry and composition. At low coverage (below 2 ML) a dramatic dependence of structure and composition on the oxygen-to-nickel flux ratio has been observed. Low oxygen dosage induces a (2×1) reconstruction in the 1-ML films that evolves to a ( 1×1) phase as the dosage and/or the film thickness increases. In the layers prepared at low oxygen dosage a large fraction of metallic Ni coexists with the Ni oxide, but the oxidized fraction largely prevails for high oxygen dosage. The oxygen dosage during the growth also affects thicker films. The mosaic formation, which has been ascribed to misfit strain relaxation, is related to a low oxygen-to-nickel flux ratio.