3 research outputs found
Epitaxial Growth of a Single-Crystal Hybridized Boron Nitride and Graphene layer on a Wide-Band Gap Semiconductor
Vertical and lateral heterogeneous structures of two-dimensional (2D)
materials have paved the way for pioneering studies on the physics and
applications of 2D materials. A hybridized hexagonal boron nitride (h-BN) and
graphene lateral structure, a heterogeneous 2D structure, has been fabricated
on single-crystal metals or metal foils by chemical vapor deposition (CVD).
However, once fabricated on metals, the h-BN/graphene lateral structures
require an additional transfer process for device applications, as reported for
CVD graphene grown on metal foils. Here, we demonstrate that a single-crystal
h-BN/graphene lateral structure can be epitaxially grown on a wide-gap
semiconductor, SiC(0001). First, a single-crystal h-BN layer with the same
orientation as bulk SiC was grown on a Si-terminated SiC substrate at 850 oC
using borazine molecules. Second, when heated above 1150 oC in vacuum, the h-BN
layer was partially removed and, subsequently, replaced with graphene domains.
Interestingly, these graphene domains possess the same orientation as the h-BN
layer, resulting in a single-crystal h-BN/graphene lateral structure on a whole
sample area. For temperatures above 1600 oC, the single-crystal h-BN layer was
completely replaced by the single-crystal graphene layer. The crystalline
structure, electronic band structure, and atomic structure of the h-BN/graphene
lateral structure were studied by using low energy electron diffraction,
angle-resolved photoemission spectroscopy, and scanning tunneling microscopy,
respectively. The h-BN/graphene lateral structure fabricated on a wide-gap
semiconductor substrate can be directly applied to devices without a further
transfer process, as reported for epitaxial graphene on a SiC substrate.Comment: 23 pages, 7 figure
Reliability Enhancement of Germanium Nanowires Using Graphene as a Protective Layer: Aspect of Thermal Stability
We
synthesized thermally stable graphene-covered Ge (Ge@G) nanowires
and applied them in field emission devices. Vertically aligned Ge@G
nanowires were prepared by sequential growth of the Ge nanowires and
graphene shells in a single chamber. As a result of the thermal treatment
experiments, Ge@G nanowires were much more stable than pure Ge nanowires,
maintaining their shape at high temperatures up to 850 °C. In
addition, field emission devices based on the Ge@G nanowires clearly
exhibited enhanced thermal reliability. Moreover, field emission characteristics
yielded the highest field enhancement factor (∼2298) yet reported
for this type of device, and also had low turn-on voltage. Our proposed
approach for the application of graphene as a protective layer for
a semiconductor nanowire is an efficient way to enhance the thermal
reliability of nanomaterials