COLLOQUIUM: Transport through graphene : from suspended multi-terminal devices to graphene on new substrates
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COLLOQUIUM: Transport through graphene : from suspended multi-terminal devices to graphene on new substrates
CIC nanoGUNE Seminars
- Speaker
-
Prof. Alberto Morpurgo, University of Geneva
- When
-
2013/10/07
13:00
- Place
- nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian
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-
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![COLLOQUIUM: Transport through graphene : from suspended multi-terminal devices to graphene on new substrates](/++theme++dipc-theme/img/event_image_berdea.png)
**Host** : Jose M. Pitarke
One of the goals of graphene research is to improve the quality of devices for
both fundamental studies and practical applications. In practice, this means
to understand and minimize sources of extrinsic disorder. Since graphene is
only one atom thick and normally –especially for layers exfoliated from
natural graphite- it has very high chemical purity and structural perfection,
much of the disorder originates from external materials in proximity to
graphene, such as the substrate or adsorbates. One strategy to improve the
quality of graphene, therefore, is to remove the substrate and perform
transport measurements on suspended samples. Indeed measurements of this type
have shown that suspended graphene has the highest possible quality.
Unfortunately, for technical reasons, most suspended graphene devices have
been realized in a two-terminal configuration, which limits the kind of
experiments that are possible. In the first part of the talk I will show how
multi-terminal suspended devices of very high-quality can be realized, and how
they can be used to reveal new phenomena. In particular, I will discuss the
observation of fractional quantum Hall effect in suspended multi-terminal
bilayer graphene devices, with one of the most pronounced states occurring at
even denominator filling of 1/2 , possibly being an experimental realization
of a Moore-Read state. In the second part of the talk, I will discuss attempts
to improve the quality of graphene on substrate, by using new materials.
Specifically, I will discuss the case of SrTiO3 substrates, having dielectric
constant approximately 1000 times larger than SiO2, and of h-BN substrates.
Systematic studies on these substrates provide important new information.
Specifically, we can conclude directly from the data that the microscopic
mechanism that limits the mobility is also responsible for the carrier non-
homogeneity that is observed in the experiments. Our analysis also strongly
suggests that this mechanism is related to the presence of strain in the
graphene layers.