Sheath structure of an electronegative plasma with cold positive ions

The one-dimensional collisionless sheath model of electropositive plasmas is extended here to study the sheath structure of an electronegative plasma at steady state with the assumptions of cold positive ions and planar sheath configurations, Similar to the electropositive plasma sheath, a net charge layer is built within the sheath. However, the net charge density distribution within the sheath is sensitive to the plasma electronegativity (ratio of negative ion density n(-b) to the electron density n(eb)), It is most interesting that the sheath thickness varies nonmonotonically with the plasma electronegativity of the bulk plasma. Last, the effects of applied wall potential and temperature ratio of electrons to negative ions are discussed.