Effect of MeV ion induced heating on secondary electron emission from Si surface and estimation of local temperature

We report the variation of secondary-electron yield and target temperature with the variation of ion beam intensity during 100 MeV N+5 bombardment on Si surfaces. Theoretical understanding of secondary-electron emission during ion bombardment predicts no variation of yield with ion beam intensity. We discovered that the variation of secondary-electron yield arises due to the rise of local temperature at ion impact sites of the target. The secondary-electron yield first decreases with the increase of ion beam current but subsequently, it increases with the further rise of beam current. The initial decrease is due to the temperature-dependent change of electrochemical potential of Si. The considerable increase of the secondary-electron yield with a further increase of ion beam current is caused by local surface heating and subsequent additional thermionic electron emission. We have estimated the surface temperature of ion-impact sites by separating the thermionic electron current from the collisional secondary electron current.