Biomedical Engineering Reference
In-Depth Information
(a)
(b)
-3 × 10
11
-3 × 10
9
Untreated
Treated
Untreated
Treated
-2 × 10
9
-2 × 10
11
-1 × 10
9
-1 × 10
11
0
0
1 × 10
11
2 × 10
11
3 × 10
11
1 × 10
9
2 × 10
9
3 × 10
9
0
0
Z'
(ohm)
Z'
(ohm)
FIGURE 4.28
(a) Impedance spectroscopy of treated and untreated SCD samples. (b) High-frequency impedance data. The
solid line is a mathematical fitting to the semicircular response of the untreated device. (From Bevilacqua, M.,
Appl. Phys. Lett.
, 95, 243501, 2009. With permission.) [151]
Ultraviolet Sensors
Bevilacqua et al. [151] successfully fabricated diamond as a UV photodetector in 1995. Recently,
their group invested SCD in this area and found that it represented an extreme sensitivity
to deep UV light. The SCD, which had an rms value of 3.5 nm, was performed a passivation
treatment in an environment full of methane at about 700°C for 15 min, and then annealed
at a temperature of 400°C for 1 h. The frequency range of the impedance spectroscopy mea-
surement was varied from 0.1 Hz up to 10 MHz. The Nyquist plot is shown in Figure 4.28.
The impedance spectroscopy is plotted by real component,
Z
→
versus imaginary compo-
nent
Z
→
for both treated and untreated SCD samples in Figure 4.28. The presence of imped-
ance spectroscopy plot indicates that the equivalent circuit of the SCD sample is a resistance
parallel with a capacitance (
R
-
C
parallel circuit). After using mathematical method fit on
the data, the resistance/capacitance value after passivation treatment is simulated to be 8 ×
10
11
Ω
/0.5 pF with untreated surface and 1 × 10
11
Ω
/3 pF, respectively. The high-frequency
impedance is given in Figure 4.28b, and the solid semicircular line is a mathematical fit-
ting, where R/C value is 4 × 10
9
Ω
/0.3 pF. The author explained that the disorder materials
on the surface of the SCD samples were removed, so a lower resistivity was conducted
from the impedance spectroscopy measurement. After the passivation process, the exter-
nal quantum efficiency was more comparably optimistic than other homoepitaxial films
and it enhanced the UV photoconductive device performance.
Non-Diamond-BasedMaterialsforBiologicalApplication
Non-diamond carbon-related materials include multiwalled carbon nanotubes (MWCNTs),
DLC, hydrogenated amorphous carbon (a-C:H), fullerene, and graphene. They have a wide
range of applications in different fields, and EIS is also introduced as an assistance to find
their performance in specific areas.
