Biomedical Engineering Reference
In-Depth Information
etching for hydrogen thermal desorption (TD) have been performed
using scanning tunneling microscope (STM) and atomic force
microscope (AFM). The surface morphology of untreated reference
HOPG samples revealed by STM was found atomically flat (Fig. 2.21a),
with a typical periodic structure of graphite (Fig. 2.21b). Exposure of
the reference HOPG samples (30-125 min at a pressure of about 1 Pa
and near-room temperature) to different atomic hydrogen doses (D)
has drastically changed the initially flat HOPG surface into a rough
surface, covered with bumps-blisters (Fig. 2.21c) with the average
height, as shown in Fig. 2.21d, of about 4 nm.
Figure 2.21
STM images of the untreated HOPG sample (under ambient
conditions) taken from areas of
(a) 60.8 × 60.8 nm and (b)
10.9 × 10.9 nm [high resolution image of the square in image
(a)]. (c) AFM image (area of 1 × 1 nm) of the HOPG sample
subjected to atomic hydrogen dose (
/
cm
2
. (d) Surface height profile obtained from the AFM image
reported in (c). The STM tunnel
D
) of 1.8 × 1016 H
0
V
and current are 50-100
bias
mV and 1-1.5 mA, respectively [5].
