Abstracts Book - IMRC 2018

• SD5-O001 Invited Talk
ATOMIC RESOLUTION IN-SITU IMAGING OF 2D MATERIALS AT
ELEVATED TEMPERATURES AND UNDER ELECTRICAL BIASING
Jamie Warner 1
1 University of Oxford, Materials, United Kingdom, Channel Islands & Isle of Man.
Structural transformations in monolayer MoS2 and WS2 2D crystals are studied
at the atomic scale using low-voltage aberration corrected TEM. The influence of
thermal annealing effects on the line defects and edge terminations is revealed
using SiN based chips for in-situ studies. I will show how thermally activated
vacancy diffusion enables ultralong vacancy lines of up to 70nm to form in MoS2,
and how the interaction between vacancy lines causes large scale inversion
domains and void formation. At high temperatures of 800oC atomically flat
edges of MoS2 are produced and have Mo rich terminations. Excessive vacancy
migration to the edges at high temperatures causes MoS wires to form at the
edges. I will also show our recent work on in-situ studies of 2D materials under
electrical bias. Nanofabrication methods are used to pattern electrodes and
then 2D crystals of WS2 are transferred across suspended electrodes to study
electrical breakdown mechanisms. Under high electrical bias, WS2 decomposes
by the loss of S atoms and leaves W clusters. Importantly, the current increases
through the channel due to the increased graphitization of surface carbon
adsorbates. These studies show how in-situ monitoring of structure can help
understand electrical fluctuations in 2D devices.
Acknowledgment:
JHW thanks the Royal Society and the ERC for support.
Keywords: TEM, 2D materials, heating
Presenting authors email: jamie.warner@materials.ox.ac.uk