posted on 2020-12-22, 20:05authored byAnkur Nipane, Min Sup Choi, Punnu Jose Sebastian, Kaiyuan Yao, Abhinandan Borah, Prathmesh Deshmukh, Younghun Jung, Bumho Kim, Anjaly Rajendran, Kevin W. C. Kwock, Amirali Zangiabadi, Vinod M. Menon, P. James Schuck, Won Jong Yoo, James Hone, James T. Teherani
The
development of a controllable, selective, and repeatable etch
process is crucial for controlling the layer thickness and patterning
of two-dimensional (2D) materials. However, the atomically thin dimensions
and high structural similarity of different 2D materials make it difficult
to adapt conventional thin-film etch processes. In this work, we propose
a selective, damage-free atomic layer etch (ALE) that enables layer-by-layer
removal of monolayer WSe2 without altering the physical,
optical, and electronic properties of the underlying layers. The etch
uses a top-down approach where the topmost layer is oxidized in a
self-limited manner and then removed using a selective etch. Using
a comprehensive set of material, optical, and electrical characterization,
we show that the quality of our ALE processed layers is comparable
to that of pristine layers of similar thickness. The ALE processed
WSe2 layers preserve their bright photoluminescence characteristics
and possess high room-temperature hole mobilities of 515 cm2/V·s, essential for fabricating high-performance 2D devices.
Further, using graphene as a testbed, we demonstrate the fabrication
of ultra-clean 2D devices using a sacrificial monolayer WSe2 layer to protect the channel during processing, which is etched
in the final process step in a technique we call sacrificial WSe2 with ALE processing (SWAP). The graphene transistors made
using the SWAP technique demonstrate high room-temperature field-effect
mobilities, up to 200,000 cm2/V·s, better than previously
reported unencapsulated graphene devices.