It is described as a decrease in shielding effort between the nucleus and last orbital due to electrons present between them i.e., greater the screening effect, easier the removal of electron. In solids, especially in metals and semiconductors, the electrostatic screening or screening effect reduces the electrostatic field and Coulomb potential of an ion inside the solid. Like the electric field of the nucleus is reduced inside an atom or ion due to the shielding effect, the electric fields of ions in conducting solids are further reduced by the cloud of conduction electrons. The screened Coulomb potential is expressed as