Interaction of hydrogen with a nickel surface in the low-temperature field evaporation

Abstract

The process of field evaporation of nickel in hydrogen atmosphere under pressure 10 −6 Pa at 20 K was investigated using a high resolution pulsed-laser time-of-flight atom-probe field ion microscope. Under these conditions, the ions of H +, H 2 + and H 3 + were detected as well as those of Ni 2+, Ni + and NiH x + ( x = 1 –3). On the basis of both: experimentally determined energy distribution of ions and ab initio calculations in the density-functional theory (DFT) for Ni–H, including external homogeneous electrostatic fields, we can state that hydrogen atoms are bound to the nickel surface in the presence of the electrostatic field of strength about 30 V/nm. These complex ions are formed within two topmost layers at the nickel surface in the high electric field applied.