Chen Yi-Feng, Hsu Hung-Chang, Chen Hao-Yu, Chen Liang-Yu, Lin Yan-Ruei, Li Ming-Yang, Radu Iuliana P, Chiu Ya-Ping
Graduate School of Advanced Technology, National Taiwan University, Taipei 10617, Taiwan.
Department of Physics, National Taiwan University, Taipei 10617, Taiwan.
ACS Nano. 2025 May 27;19(20):19408-19416. doi: 10.1021/acsnano.5c03676. Epub 2025 May 15.
The interlayer coupling between metals and the two-dimensional (2D) semiconductors' conduction band (CB), encompassing metal-induced gap states (MIGS) and valley band modulation, critically influences both the Schottky barrier height (SBH) and intrinsic sheet resistance. Understanding the CB modulation induced by metals/semimetals is, therefore, essential for contact engineering optimization. Given that the MIGS decay length and orbital interactions are spatially confined to the nanoscale region proximate to the 2D semiconductor interface, we employed scanning tunneling microscopy/spectroscopy to quantitatively determine the MIGS decay length and CB minimum on various metal/semimetal substrates. This approach enabled the comprehensive characterization of MIGS distribution, charge neutrality level variation, and SBH properties. Our findings demonstrate that maintaining valley band structure integrity during semimetal interlayer coupling facilitates reduced intrinsic sheet resistance. These results elucidate the mechanism underlying weak interlayer coupling at semimetal-2D semiconductor junctions and their superior contact transport performance, providing insights into the rational design of future 2D-based devices.
金属与二维（2D）半导体导带（CB）之间的层间耦合，包括金属诱导能隙态（MIGS）和谷带调制，对肖特基势垒高度（SBH）和本征薄层电阻都有至关重要的影响。因此，了解金属/半金属引起的CB调制对于接触工程优化至关重要。鉴于MIGS衰减长度和轨道相互作用在空间上局限于靠近2D半导体界面的纳米级区域，我们采用扫描隧道显微镜/光谱法定量确定了各种金属/半金属衬底上的MIGS衰减长度和CB最小值。这种方法能够全面表征MIGS分布、电荷中性水平变化和SBH特性。我们的研究结果表明，在半金属层间耦合过程中保持谷带结构完整性有助于降低本征薄层电阻。这些结果阐明了半金属-2D半导体结处弱层间耦合及其优异接触传输性能的潜在机制，为未来基于2D的器件的合理设计提供了见解。
