The purpose of the present study is to demonstrate the feasibility of plasma treated silicon field emission arrays used as a charge neutralization device in ion implantation system. Silicon field emission arrays (Si-FEAs) were treated in plasma to form carbonized layer. Electron emission properties of the plasma treated Si-FEAs have been measured in various gaseous ambient. The examined gases were hydrogen, oxygen, methane, carbon monoxide and carbon dioxide. Either gas was introduced to the vacuum chamber until the pressure reaches to the partial pressure in the ion implantation system