Two-dimensional plasma sheath observations in plasma source ion implantation.
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Date
1996
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Abstract
Plasma Source Ion Implantation (PSII) is the process of implanting high energy ions
[10-50 keV] into metallic targets, by pulsing them negatively whilst immersed in a
background plasma. PSII achieves surface hardening, and increased wear and corrosion
resistance.
Numerous papers have been published describing numerical simulations and models
of the PSII process, most of which have been limited to one dimension.
This thesis presents the results of work carried out III the Plasma Processing
Laboratory at the University of Natal, Durban, during 1994-1995. In particular,
measurements of two-dimensional plasma sheath effects due to spherical and complex
shaped targets are compared with a particle-in-cell simulation code.
The simulation results are used to define a relationship between the plasma potential
of the sheath edge and the saturation currents. Thus allowing for the saturation
currents to be used to trace sheath evolution. These results are compared with the
experimental measurements from the spherical target.
Results from the rectangular and complex saw-tooth targets show a lack of sheath
conformality. The ion saturation currents were susceptible to electron swamping,
which occured in localised regions associated with target structure. It is thought that
secondary electrons ejected from the target are focused and accelerated by the high
target potential into these regions, where they swamp the ion current.
Description
Thesis (M.Sc.)-University of Natal, Durban, 1996.
Keywords
Plasma (Ionized Gases), Ion implantation., Theses--Physics., Corrosion and anti-corrosives.