Biomedical Engineering Reference
In-Depth Information
(HOPG) surface exposed to atomic hydrogen [9]. In Ref. [5] it was also
supposed that during TD process a small amount of hydrocarbons
could be formed and released together with hydrogen, accounting
for bigger sized etch-pits of nearly circular shapes.
These and some other observations of net flat HOPG surfaces in
the TD case and after successive STM scannings, induced the author
of Ref. [5] to propose the model shown in Fig. 2.23. According to
this model, bumps found on HOPG surface after exposure to atomic
hydrogen (Fig. 2.21c) are simply graphite blisters, containing inside
hydrogen gas in molecular form.
Graphite
Monolayer
Figure 2.23
Model showing the hydrogen accumulation in HOPG, forming
blister-like structures. (a) Pre-atomic hydrogen interaction
step. (b) H
captured inside graphene blisters, after the
interaction step. Sizes are not drawn exactly in scale [5].
2,
As is supposed, due to a small diameter of atomic hydrogen in
comparison with a hole size, atomic hydrogen intercalates in graphite
between the layers through the holes in graphene hexagons. Then,
being converted in H
gas form, is captured inside the graphene
blisters due to the relatively large kinetic diameter of hydrogen
2
