The recent work on stanene as quantum spin Hall insulators made us investigate bilayer stanene using first principle calculations. With an aim of improving and developing new properties, via modulating the stacking order (and angle) of the bilayers. This stacking of layers has been proven technique for modulating the properties of monolayer materials. Here we design multiple bilayer systems, with different stacking angles and AA and AB configurations. Rather observing an improvement in bandgap due to spin-orbit coupling (SOC), we witness a splitting of the band due to SOC, a characteristic behavior of stacked MoS2 sheets. This splitting of the bands gives rise to different, independent and distinct spin-up and spin-down channels, manifesting a valley dependent spin polarization. Also, as a contrast to stacked MoS2 system we notice in our system the stacking angle and order, does effect electronic states.
Graphene
and its heterostructures exhibit interesting electronic
properties and are explored for quantum spin Hall effect (QSHE) and
magnetism-based device applications. In present work, we propose a
heterostructure of graphene encapsulated by hydrogenated-graphene,
which could be a promising candidate for a variety of device applications.
We have carried out DFT calculations on this system to check its feasibility
to be a versatile material. We found that electronic states of multilayer
pristine graphene, especially the Dirac cone, an important feature
to host QSHE, can be preserved by sandwiching it by fully hydrogenated
graphene. The interference of electronic states of hydrogenated graphene
was insignificant with those of graphene. States of graphene were
also found to be stable upon application of an electric field up to
±2.5 V/nm. For device applications, multilayer graphene or its
heterostructures are required to be deposited on a substrate, which
interacts with the system opening up a gap at the Dirac cone making
it less suitable for QSHE applications, and hydrogenated graphene
can prevent it. Magnetization in these hydrogenated-graphene-sandwiched
graphene systems may be induced by creating vacancies or distortions
in hydrogenated graphene, which was found to have a minimal effect
on graphene’s electronic states, thus providing an additional
degree of manipulation. We also performed a set of calculations to
explore its applicability for detecting some molecules. Our results
on trilayer graphene encapsulated by hydrogenated graphene indicate
that all these observations can be generalized for systems with a
larger number of graphene layers, indicating that multilayer graphene
sandwiched between two hydrogenated graphene is a versatile material
that can be used in QSHE and sensor devices.
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