Chemistry Reference
In-Depth Information
TABLE 8.12
Comparison of Conventional and Plasma Methods
Conventional Surgery
Plasma Treatment
Tissue is removed by excision/burning
Tissue is removed by chemical stimuli
Necrosis always occurs
Necrosis is avoided
Causes wounds
May heal wounds
Inflammation and scarring occurs
Inflammation and scarring can be avoided
Massive tissue removal is possible
Only superficial tissue removal is possible
Tissue irregularities are excised
Irregular surfaces can be treated
Depth effects are difficult to control
High precision can be reached
Conventional Medicine
Plasma Treatment
Drugs are delivered systemically
Plasma is delivered topically
The whole organism is influenced
Only diseased parts are influenced
Long-living species (drugs) are used
Short living species are used
Specific chemistry is involved
Basic
physiological chemistry is involved
Source:
From Stoffels, E., Atmospheric plasma: A universal tool for physicians? In R.
Hippler, H. Kersten, M. Schmidt, and K. Schoenbach, eds.,
Low Temperature
Plasmas
, 2 edn., Wiley, Weinheim, Germany, p. 837, 2008.
be identified [283]. For some potential fields of medical applications, a comparison
of conventional and plasma methods is presented in Table 8.12.
A lot of fundamental research as well as of technological development will be
necessary in future, distinguished by interdisciplinary work of plasma physicists,
biologists, chemist, and physicians.
8.2.4 P
LASMA
-E
NHANCED
C
HEMICAL
V
APOR
D
EPOSITION
Chemical vapor deposition [284] involves chemical reactions of reactants in the gas
phase and/or on the substrate surface, which leads to the deposition of materials
also as thin films. Activation processes such as thermal, photo-assisted, and, last but
not least, plasma-assisted procedures are successful applied deposition technologies.
Plasma-assisted chemical vapor deposition (PACVD) uses the energy content of the
plasma, in nonthermal plasmas primary the energy of the hot electron gas.
Advantages of PACVD is the low temperature of the substrate, e.g., Si
3
N
4
depo-
sition required in a thermal-activated CVD process temperatures is in the range of
800
◦
C-900
◦
C; PACVD formation of Si
3
N
4
films using a SiH
4
/NH
3
operates near
350
◦
C. Coating of temperature-sensitive substrates is possible. Disadvantages of
PACVD technology are sometimes the application of low-pressure plasmas, which
need expensive vacuum technique. The action of energetic ions on the deposition
process has also to be taken into account.
Plasma-enhanced atomic layer deposition (PEALD) is based on a sequential use
of self-terminating plasma-enhanced gas solid reactions, which leads to a coverage of
the target surface by a monolayer film with good conformality. Metal-oxide films are
depositedbyapplicationofmetal-organicprecursorsandO
2
plasmasasoxidant[285].
