Stimulation of secondary negative ion emission by implantation of alkaline ions into the surface layer of a solid followed by heating

A new method of stimulating secondary negative ion emission is suggested that is based on implantation of alkaline ions into the surface layer of a solid with subsequent heating to a temperature providing optimal coverage of the surface (about half a monolayer) by activator (alkaline) ions. It is shown that, by appropriately selecting the implantation dose (10¹⁸–10¹⁹ cm⁻³) and surface temperature (500–900°C), one can reach such a degree of coverage of the sample surface by activator ions that its work function eφ becomes minimal: 1.9 eV for molybdenum and 2.1 eV for copper. It is found that, with the implantation (irradiation) dose and surface temperature chosen properly, one can, by means of outdiffusion of cesium atoms, achieve such a degree of surface coverage that remains unchanged during the continuous sputtering of the surface by a cesium ion beam.