  The sheath formation in a weakly magnetized collisionless electronegative
plasma consisting of electrons, negative and positive ions has been numerically
investigated using the hydrodynamic equations. The electrons and negative ions
are assumed to follow Boltzmann relation. A sheath formation criterion has been
analytically derived. The paper focuses on studying the sheath structure by
varying the electronegativity. It has been observed that the presence of
negative ions has a substantial effect on the sheath structure. The
observations made in the present work have profound significance on processing
plasmas, especially in the semiconductor industry as well as in fusion studies.
