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

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

The book "Defects in Two-Dimensional Materials" is available for pre-order

Defects in Two-Dimensional Materials
1st Edition

Editors: Rafik Addou & Luigi Colombo
Paperback ISBN: 9780128202920
Imprint: Elsevier
Published Date: 1st March 2022
Page Count: 454

Order here

Table of Contents

1. Introduction
Rafik Addou and Luigi Colombo
2. Physics and theory of defects in two-dimensional materials: The role of reduced dimensionality
Hannu-Pekka Komsa and Arkady V. Krasheninnikov
3. Defects in two-dimensional elemental materials beyond graphene
Paola De Padova, Bruno Olivieri, Carlo Ottaviani, Claudio Quaresima, Yi Du, Mieczyslaw Jalochowski, and Mariusz Kraviec
4. Defects in transition metal dichalcogenides
Stephen J. McDonnell and Petra Reinke
5. Efforts in realizing electronic-grade graphene and h-BN
Vitaliy Babenko and Stephan Hofmann
6. Efforts in realizing electronic grade transition metal dichalcogenide materials
Yu-Chuan Lin, Riccardo Torsi, Nicholas A. Simonson, and Azimkhan Kozhakhmetov, and Joshua A. Robinson
7. Materials engineering: Defect passivation and healing
Yu Li Huang, Rebekah Chua, and Andrew Thye Shen Wee
8. Nonequilibrium synthesis and Processing Approaches to Tailor Heterogeneity in 2D Materials
David B. Geohegan, Kai Xiao and Alex A. Puretzky, Yu-Chuan Lin, Yiling Yu, and Chenze Liu
9. Two-dimensional materials under ion irradiation: From defect production to structure and property engineering
Mahdi Ghorbani-Asl, Silvan Kretschmer, and Arkady V. Krasheninnikov
10. Tailoring Defects for 2D Electrocatalysts
Leping Yang, Yuchi Wan, and Ruitao Lv
11. 2D Defects and Devices: Outlook and Perspectives
Amritesh Rai, Anupam Roy, Amithraj Valsaraj, Sayema Chowdhury, Deepyanti Taneja, Yaguo Wang, Leonard Register, and Sanjay Banerjee
12. Concluding remarks
Rafik Addou and Luigi Colombo


Defects in Two-Dimensional Materials addresses the fundamental physics and chemistry of defects in 2D materials and their effects on physical, electrical and optical properties. The book explores 2D materials such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMD). This knowledge will enable scientists and engineers to tune 2D materials properties to meet specific application requirements. The book reviews the techniques to characterize 2D material defects and compares the defects present in the various 2D materials (e.g. graphene, h-BN, TMDs, phosphorene, silicene, etc.).

As two-dimensional materials research and development is a fast-growing field that could lead to many industrial applications, the primary objective of this book is to review, discuss and present opportunities in controlling defects in these materials to improve device performance in general or use the defects in a controlled way for novel applications.

Key Features
Presents the theory, physics, and chemistry of 2D materials
Catalogues defects of 2D materials and their impacts on materials properties and performance
Reviews methods to characterize, control and engineer defects in 2D materials

Materials Scientists and Engineers, Physicists, Electrical Engineers

New Paper: How thick is thick for electrocatalytic activity?

Exciting news! A recent study published in Small titled ‘Contribution of the Sub-Surface to Electrocatalytic Activity in Atomically Precise La0.7Sr0.3MnO3 Heterostructures’ provides new insight into designing efficient electrocatalytic nanomaterials and core-shell architectures. The study investigates the role of catalytically active sub-surface layers in electrocatalytic activity by employing atomic-scale thickness control of the La0.7Sr0.3MnO3 films and heterostructures, without altering the catalyst/electrolyte interface. The observation leads to the definition of an “electrochemically-relevant depth” on the order of 10 unit cells. Check out the paper here

New Paper

Check out this open-access paper: Molecular-scale investigation of the oxidation behavior of chromia-forming alloys in high-temperature CO2. This is a collaboration between National Energy Technology Laboratory, Oregon State University, and Pacific Northwest National Laboratory.