2 research outputs found
Highly Sensitive Flexible Photodetectors Based on Self-Assembled Tin Monosulfide Nanoflakes with Graphene Electrodes
Tin
monosulfide (SnS) nanostructures have attracted huge attention recently
because of their high absorption coefficient, high photoconversion
efficiencies, low energy cost, ease of deposition, and so on. Here,
in this paper, we report on the low-cost hydrothermal synthesis of
the self-assembled SnS nanoflake-like structures in terms of performance
for the photodetectors. High-performance photodetectors were fabricated
using SnS nanoflakes as active layers and graphene as the lateral
electrodes. The SnS photodetectors exhibited excellent photoresponse
properties with a high responsivity of 1.7 × 10<sup>4</sup> A/W
and have fast response and recovery times. In addition, the photodetectors
exhibited long-term stability and strong dependence of photocurrent
on light intensity. These excellent characteristics were attributed
to the larger surface-to-volume ratio of the self-assembled SnS nanoflakes
and the effective separation of the photogenerated carriers at graphene/SnS
interfaces. Additionally, a flexible photodetector based on SnS nanoflakes
was also fabricated on a flexible substrate that demonstrated similar
photosensitive properties. Furthermore, this study also demonstrates
the potential of hydrothermal-processed SnS nanoflakes for high-performance
photodetectors and their application in flexible low-cost optoelectronic
devices
Laterally Selective Oxidation of Large-Scale Graphene with Atomic Oxygen
Using
X-ray photoemission microscopy, we discovered that oxidation
of commercial large-scale graphene on Cu foil, which typically has
bilayer islands, by atomic oxygen proceeds with the formation of the
specific structures: though relatively mobile epoxy groups are generated
uniformly across the surface of single-layer graphene, their concentration
is significantly lower for bilayer islands. More oxidized species
like carbonyl and lactones are preferably located at the centers of
these bilayer islands. Such structures are randomly distributed over
the surface with a mean density of about 3× 10<sup>6</sup> cm<sup>–2</sup> in our case. Using a set of advanced spectromicroscopy
instruments including Raman microscopy, X-ray photoelectron spectroscopy
(μ-XPS), Auger electron spectroscopy (nano-AES), and angle-resolved
photoelectron spectroscopy (μ-ARPES), we found that the centers
of the bilayer islands where the second layer nucleates have a high
defect concentration and serve as the active sites for deep oxidation.
This information can be potentially useful in developing lateral heterostructures
for electronics and optoelectronics based on graphene/graphene oxide
heterojunction