Sputtering of neutral and ionic indium clusters

Abstract

Secondary neutral and secondary ion cluster yields were measured during the sputtering of a polycrystalline indium surface by normally incident-4keV Ar+ ions. In the secondary neutral mass spectra, indium clusters as large as In32were observed. In the secondary ion mass spectra, indium clusters up to Ini_8were recorded. Cluster yields obtained from both the neutral and ion channel exhibited a power law dependence on the number of constituent atoms, n, in the cluster, with the exponents measured to be-5.6 and-41, respectively. An abundance drop was observed at n=8, 15, and 16 in both the neutral and ion yield distributions suggesting that the stability of the ion (either secondary ion or photoion) plays a significant role in the z observed distributions. In addition, our experiments suggest that unimolecular decomposition of the neutral cluster may also plays an important role in the measured yield distributions.

Formation of large clusters during sputtering of silver

“…(1). This ®nding is in agreement with previous experiments on silver [8,11] as well as on other metal [6,7,14,17] and semiconductor [18] surfaces. The value of the exponent d observed here (3.7), however, is signi®-cantly lower than those observed in our previous work [8,14].…”

“…For the speci®c case of sputtered silver clusters, a¯u-orine laser operated at a wavelength of 157 nm provides an ideal post-ionization tool, since the photon energy of 7.9 eV is larger than the ionization potential of silver atoms and all homonuclear silver clusters [10]. Using the technique described above, it has in the past been possible to detect neutral Cu n [4,6], Al n [6], In n [7] and Ag n [8] clusters up to sizes of n 20, 12, 30 and 19, respectively, which have been sputtered from the respective clean surfaces under bombardment with rare gas ions of energies up to 5 keV. In all these experiments, relative cluster yields ± i.e., the cluster yields normalized to that of sputtered monomers ± have been found to obey a power law dependence on the cluster size according to…”

Nonadditive sputtering of silicon by keV energy molecular projectiles of heavy and light elements

“…In this model the binding energy between atoms in the impact region of sputtered metals is used as fitting parameter. A comparison of experimental data [14] (mass spectra of the Al n , Ag n , Nb n , and Ta n neutral clusters sputtered from the Al, Ag, Nb, and Ta targets by atomic Ar ϩ projectiles with the energy of 5 keV) with the calculated ones [27] shows a satisfactory agreement if well-known tabled values of the binding energy are used. It is important that the experimental results obtained in [23][24][25] for Nb n ϩ and Ta n ϩ cluster ions can be directly compared with calculations of the model [27] because, as it was shown in [28], the anomalous high nonadditivity of sputtering in the form of large Nb n ϩ and Ta n ϩ cluster ions (n Ͼ 4) under molecular ion bombardment originates from nonadditive sputtering rather than processes associated with the charge state formation of sputtered particles.…”

Formation of neutral clusters during sputtering of gold

“…Previously, postionisation studies of neutral cluster formation has been observed during the sputtering of Ag [7,8], In [9], Al and Cu [10], Nb and Ta [11], Ga [12] and Ge [13]. From these measurements, a power law dependence has been established [9,14] for the yield, Y n , of a cluster of n atoms, i.e.…”

“…From these measurements, a power law dependence has been established [9,14] for the yield, Y n , of a cluster of n atoms, i.e. Y n $ n Àd ð1Þ…”