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St John’s Title A Fellow
Senior Research Associate

BE Jiangnan University
MSc Peking University
PhD University of Cambridge

My research is on atomically thin semiconductors (e.g. MoS2, WS2, WSe2, MoSe2) for ultra-low power electronic devices. I study the fundamental properties of metal/semiconductor and semiconductor/dielectric interfaces and investigate methods to make them as clean as possible. I develop methods to study these interfaces using imaging, spectroscopic, and electronic techniques. My aim is to fabricate novel low energy devices based on atomically thin semiconductors. 

van der Waals contacts

A key challenge in realizing high performance electronic devices based on atomically thin semiconductors is making ultra-clean metal contacts. My approach has focused on realising van der Waals metal contacts that allow efficient injection of electrons, holes, and spins into atomically thin semiconductors.

Semiconductor/dielectric interfaces

Non-ideal semiconductor/dielectric interfaces with high defect states can result in hysteresis, low current, reduced stability in electronic devices. We study interfaces between atomically thin semiconductors and dielectrics using synchrotron photoemission spectroscopy. We then correlate the interface electronic structure with device performance – demonstrating that clean interfaces lead to near ideal field effect transistors. 

Ferroelectric van der Waals (vdW) heterostructures

The emergence of ferroelectricity in heterostructures of atomically thin semiconductors (referred to as vdW heterostructures) opens new avenues for the development of non-volatile memory devices, in-memory computing electronics, and optoelectronics. My research focuses on characterising polarisation states in ferroelectric vdW heterostructures and integrating them with multiple pristine interfaces to achieve low-power electronic devices.

Clean van der Waals interface between Pt and WSe2 for holes injection.

  • Yan Wang, Soumya Sarkar, Han Yan, Manish Chhowalla, “Critical challenges in the development of electronics based on two-dimensional transition metal dichalcogenides”, Nature Electronics (2024)
  • Yan Wang, Jong Kim, Yang Li, Kyung Yeol Ma, Seokmo Hong, Minsu Kim, Hyeon Suk Shin, Hu Young Jeong, Manish Chhowalla, “P-type electrical contacts for 2D transition metal dichalcogenides”, Nature, 610, 61–66 (2022)
  • Yan Wang, Manish Chhowalla, “Making clean electrical contacts on 2D transition metal dichalcogenides”, Nature Reviews Physics, 4, 101–112 (2022)
  • Yan Wang, Jong Chan Kim, Ryan J. Wu, Jenny Martinez, Xiuju Song, Jieun Yang, Fang Zhao, Andre Mkhoyan, Hu Young Jeong, Manish Chhowalla. “Ultra-clean van der Waals contacts between three-dimensional metals and two-dimensional semiconductors”, Nature, 568, 70–74 (2019)