Substrate-Structure Dependence of Ag Electromigration on Au-Precovered Si(111) Surfaces
Substrate-Structure Dependence of Ag Electromigration on Au-Precovered Si(111) Surfaces
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Au 预覆盖的 Si(111) 表面上 Ag 电迁移的基底结构依赖性
DOI：
10.1143/jjap.39.4438
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发表时间：
2000
影响因子：
1.5
通讯作者：
S. Hasegawa
中科院分区：
文献类型：
--
作者：
Fangxiao Shi;I. Shiraki;T. Nagao;S. Hasegawa
利用原位微区真空扫描电镜和微探针反射高能电子衍射（RHEED）研究了Ag在Au预镀Si（111）表面上的电迁移。银膜贴片的迁移行为强烈依赖于Au覆盖度θAu和相应的表面结构。当θAu<0.7单层（ML）时，贴片优先向阴极扩展，达到最大面积，其中Ag和Au的覆盖率之和总是约1 ML，而与θAu无关，导致具有不同Au/Ag浓度比的二维（2D）合金相（显示为103 × 103的RHEED图案）。在（5×2+α-Au 3× Au 3）-Au混合相结构（θAu = 0.7 ML）上实现了贴片面积的最大扩展。而当θAu>0.7 ML时，贴片膨胀大大减小。特别是在β-β 3× β 3-Au（θAu = 1.0 ML）表面，贴片没有向阴极方向扩展。但Ag原子在所有衬底（包括β-Al_2O_3 × Al_2O_3-Au表面）上的贴片内部迁移，在平台边缘附近形成三维岛。
Electromigration of Ag on Au-precovered Si(111) surfaces was investigated by in-situ ultrahigh vacuum scanning electron microscopy and µ-probe reflection-high-energy electron diffraction (RHEED). Migration behaviors of a Ag-film patch strongly depended on Au coverage θAu and corresponding surface structures. When θAu<0.7 monolayer (ML), the patch expanded preferentially towards the cathode to attain a maximum area in which the sum of Ag and Au coverages were always about 1 ML irrespective of θAu, resulting in two-dimensional (2D) alloy phases (showing √3×√3 RHEED patterns) with different Au/Ag concentration ratios. The largest expansion of the patch area was achieved on a (5×2+α-√3×√3)-Au mixed phase structure (θAu∼0.7 ML). However, when θAu>0.7 ML, the patch expansion was greatly reduced. Especially on the β-√3×√3-Au surface (θAu∼1.0 ML), the patch showed no directional expansion towards the cathode. But Ag atoms were observed to migrate inside the patches on all substrates (including the β-√3×√3-Au surface) to form 3D islands near terrace edges.