posted on 2021-06-21, 20:03authored byJoeson Wong, Artur Davoyan, Bolin Liao, Andrey Krayev, Kiyoung Jo, Eli Rotenberg, Aaron Bostwick, Chris M. Jozwiak, Deep Jariwala, Ahmed H. Zewail, Harry A. Atwater
van
der Waals materials exhibit naturally passivated surfaces and
an ability to form versatile heterostructures to enable an examination
of carrier transport mechanisms not seen in traditional materials.
Here, we report a new type of homojunction termed a “band-bending
junction” whose potential landscape depends solely on the difference
in thickness between the two sides of the junction. Using MoS2 on Au as a prototypical example, we find that surface potential
differences can arise from the degree of vertical band bending in
thin and thick regions. Furthermore, by using scanning ultrafast electron
microscopy, we examine the spatiotemporal dynamics of charge carriers
generated at this junction and find that lateral carrier separation
is enabled by differences in the band bending in the vertical direction,
which we verify with simulations. Band-bending junctions may therefore
enable new optoelectronic devices that rely solely on band bending
arising from thickness variations to separate charge carriers.