Gas sensors play an important role
in numerous fields, covering a wide range of applications, including
intelligent systems and detection of harmful and toxic gases. Even
though they have attracted much attention, the response time on the
order of seconds to minutes is still very slow. To circumvent the
existing problems, here, we provide a seminal attempt with the integration
of graphene, semiconductor, and an addition sieve layer forming a
nanocomposite gas sensor with ultrahigh sensitivity and ultrafast
response. The designed sieve layer has a suitable band structure that
can serve as a blocking layer to prevent transfer of the charges induced
by adsorbed gas molecules into the underlying semiconductor layer.
We found that the sensitivity can be reduced to the parts per million
level, and the ultrafast response of around 60 ms is unprecedented
compared with published graphene-based gas sensors. The achieved high
performance can be interpreted well by the large change of the Fermi
level of graphene due to its inherent nature of the low density of
states and blocking of the sieve layer to prevent charge transfer
from graphene to the underlying semiconductor layer. Accordingly,
our work is very useful and timely for the development of gas sensors
with high performance for practical applications
