Sputtering of clusters from nickel–aluminium

A NiAl(1 1 1) single crystal was bombarded with 15 keV Ar+, and the resulting secondary neutrals were analysed by laser postionisation secondary neutral mass spectrometry. By measuring the individual cluster photoion intensity as a function of laser power, the sputter yields of 33 individual clusters were determined. The yield of Aln clusters sputtered from NiAl falls with increasing cluster nuclearity as n 8.7 while Nin and Alm nNin yields are proportional to n 5.9 and n 5.2, respectively. The distribution of thee yields of mixed Alm nNin clusters with n and m is found to diverge significantly from the expected distribution based on a random combinatorial approach, indicating that the energetics due to the chemical bonding in the clusters plays a significant role during cluster formation in the sputtering process