Wang Xinglu, Hu Yaoqiao, Kim Seong Yeoul, Addou Rafik, Cho Kyeongjae, Wallace Robert M
Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States.
ACS Nano. 2023 Oct 24;17(20):20353-20365. doi: 10.1021/acsnano.3c06494. Epub 2023 Oct 3.
Tungsten transition metal dichalcogenides (W-TMDs) are intriguing due to their properties and potential for application in next-generation electronic devices. However, strong Fermi level (E) pinning manifests at the metal/W-TMD interfaces, which could tremendously restrain the carrier injection into the channel. In this work, we illustrate the origins of E pinning for Ni and Ag contacts on W-TMDs by considering interface chemistry, band alignment, impurities, and imperfections of W-TMDs, contact metal adsorption mechanism, and the resultant electronic structure. We conclude that the origins of E pinning at a covalent contact metal/W-TMD interface, such as Ni/W-TMDs, can be attributed to defects, impurities, and interface reaction products. In contrast, for a van der Waals contact metal/TMD system such as Ag/W-TMDs, the primary factor responsible for E pinning is the electronic modification of the TMDs resulting from the defects and impurities with the minor impact of metal-induced gap states. The potential strategies for carefully engineering the metal deposition approach are also discussed. This work unveils the origins of E pinning at metal/TMD interfaces experimentally and theoretically and provides guidance on further enhancing and improving the device performance.
钨过渡金属二硫属化物（W-TMDs）因其特性以及在下一代电子器件中的应用潜力而备受关注。然而，在金属/W-TMD界面处会出现强烈的费米能级（E）钉扎现象，这可能极大地限制载流子注入到沟道中。在这项工作中，我们通过考虑界面化学、能带排列、杂质以及W-TMDs的缺陷、接触金属吸附机制和由此产生的电子结构，阐明了W-TMDs上Ni和Ag接触的E钉扎起源。我们得出结论，在共价接触金属/W-TMD界面（如Ni/W-TMDs）处E钉扎的起源可归因于缺陷、杂质和界面反应产物。相比之下，对于范德华接触金属/TMD系统（如Ag/W-TMDs），导致E钉扎的主要因素是由缺陷和杂质引起的TMDs的电子改性，而金属诱导能隙态的影响较小。我们还讨论了精心设计金属沉积方法的潜在策略。这项工作从实验和理论上揭示了金属/TMD界面处E钉扎的起源，并为进一步提高和改善器件性能提供了指导。
