New Position

Excited to announce that I've started a new role as an Assistant Professor in the Department of Materials Science and Engineering at the University of Texas at Dallas.

Co-organizing the Nano and 2D Materials symposium at PacSurf 2024

I am very pleased to co-organize the Nano and 2D Materials Symposium at PacSurf 2024, which will be held in Hawaii from December 8-12. This event promises to be an excellent platform for researchers to discuss and share their latest findings in the field of surfaces, thin films, and interfaces.

We invite researchers to submit their abstracts by August 9, 2024. This is a fantastic opportunity to interact with leading experts and contribute to advancing our understanding of nano and 2D materials.

For more information, visit the PacSurf 2024 website

New Paper! Fermi Level Pinning on Tungsten Dichalcogenides

Origins of Fermi Level Pinning for Ni and Ag Metal Contacts on Tungsten Dichalcogenides

Xinglu Wang,Yaoqiao Hu, Seong Yeoul Kim, Rafik Addou, Kyeongjae Cho, and Robert M. Wallace
https://doi.org/10.1021/acsnano.3c06494

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 (EF) 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 EFpinning 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 EF 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 EF 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 EF pinning at metal/TMD interfaces experimentally and theoretically and provides guidance on further enhancing and improving the device performance

Synthesis of Micron-Sized WS2 Crystallites Using ALD and post Sulfur Annealing

This new paper reports the first synthesis of micron-sized WS2 crystals by ALD using bis(t-butylimido)bis(trimethylsilylmethyl)tungsten and H2S, followed by sulfur annealing. The films are nanocrystalline with mixed phases and impurities before annealing but show Raman peaks of WS2 and larger crystals after annealing. The substrate affects the shape of the crystals: silicon leads to flake pyramids or flowers, ZnS leads to crumpled flowers, and Al2O3 leads to thin flakes.

Synthesis of Micron-Sized WS2 Crystallites Using Atomic Layer Deposition and Sulfur Annealing

New Paper on APXPS: Thermal Decomposition of Acetic Acid on Pd(111)

Just published: Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) was used to investigate the thermal decomposition of acetic acid on Pd(111). The paper serves as an excellent demonstration of how APXPS can offer valuable insights into the intricate chemistry of surface reactions.

Ambient Pressure X-Ray Photoelectron Study on the Thermal Decomposition of Acetic Acid on Pd(111). Hoan K.K. Nguyen, Rafik Addou, Kingsley C. Chukwu, Gregory S. Herman, and Líney Árnadóttir J. Phys. Chem. C 2023, 12724, 11472–11480