Chemistry Reference
In-Depth Information
enhancement by ion bombardment of the surface will be understood as chemical
sputtering [166]. Chemical sputtering is a process in which ion bombardment induces
chemical reactions, which results in the generation of volatile erosion products.
Cleaning procedures in remote plasmas with the absence of energetic ion collisions
indicate the effectivity of O atoms [164].
H
2
plasmas are successful applied to remove oxides from metal surfaces [167,
168]. The surface layer of copper exposed to clean room air contains a surface layer
of CuO
2
,CuO,Cu(OH)
2
, and CuCO
3
. For surface cleaning, a combination of thermal
and plasma treatment is successful. Thermal treatment leads to decomposition of Cu
carbonate and Cu hydroxide with desorption of CO
2
and H
2
O. Reduction of CuO and
CuO
2
occurs by hydrogen atoms, which are generated in the H
2
plasma:
CuO
+
2H
−→
Cu
+
H
2
O;
(8.58)
Cu
2
O
+
2H
−→
2Cu
+
H
2
O.
(8.59)
The complete desorption of H
2
O needs temperatures of 150
◦
C-200
◦
C. A broad
spectrum of H
2
containing plasmas is used, from atmospheric pressure DBD [168,
169] till low pressure as 1 Pa DC discharges [170].
An interesting application is the use of hydrogen plasmas for surface cleaning
of the platinum iridium prototype kilogram from hydrocarbons and metal oxides. H
2
plasmas may enable a reproducible and damage-free cleaning process of noble metal
surfaces [171].
Low-pressure hydrogen plasma is successfully applied for restoration and con-
servation of iron artifacts. This plasma removes chlorides and prevents a fast
postcorrosionoftheobjectinhumidair[172].Increasingofsurfaceenergyisobserved
by plasma treatment of metals (Al, Cu) using an atmospheric pressure jet feed by
N
2
/O
2
mixtures [173]. Also the treatment of metal implant materials in low-pressure
plasmas results in an increased surface energy [174]. This effect may be attributed to
cleaning by removing contaminants and surface oxides.
8.2.3.2.2 Ion Implantation, Nitriding
Ion implantation is a widespread method for material treatment. The application of
separate effective ion sources for the generation of high energetic (up to
1MeV)
ion beams is a pure physical method, but application of the plasma surrounding the
treated material as source of ions leads to plasma chemistry. This plasma-based ion
implantation (PBII) operates with pulsed ion energies up to 100 keV [175].
Plasma nitriding and plasma immersion ion implantation (PIII) are effective
methods for material treatment. Improvements of material qualities concern
∼
•
Hardening
•
Frictional resistance
•
Working lifespan
•
Fatigue strength
•
Corrosion resistance
•
Biocompatibility
•
Antimicrobial properties
