Cu thin films are deposited on p-type Si （100） substrates by magnetron sputtering at room temperature. The interface reaction and atomic diffusion of Cu/SiO2/Si （100） systems are studied by x-ray diffraction （XRD） and Rutherford backscattering spectrometry （RBS）. Some significant results can be obtained. The onset temperature of interdiffusion for Cu/SiO2/Si（100） is 350~℃. With the annealing temperature increasing, the interdiffusion becomes more apparent. The calculated diffusion activation energy is about 0.91 eV. For the Cu/SiO2/Si （100） systems copper silicides are not formed below an annealing temperature of 350~℃. The formation of the copper silicides phase is observed when the annealing temperature arrives at 450~℃.
In this work, a systematic study of some possible isomer structures of the Cu5 cluster obtained from density functional theory methods is presented. The polarisation and pseudopotential basis sets are employed in the calculations. The results show that the binding energies, frequencies, coordination numbers and average bond lengths are in reasonable agreement with reported experimental data. Moreover, four isomers of the Cu5 cluster are obtained according to calculations, in which the most stable configuration is the planar structure. Meanwhile, two three-dimensional structures of the Cu5 cluster are obtained in this work, which might be valuable for further theoretical and experimental studies. In addition, our study proves the possibility of the isomer structures of the Cu5 cluster.
The soft deposition of Cu clusters on a Si （001） surface was studied by molecular dynamics simulations. The embedded atom method, the Stillinger-Weber and the Lennar-Jones potentials were used to describe the interactions between the cluster atoms, between the substrate atoms, and between the cluster and the substrate atoms, respectively. The Cu13, Cu55, and Cu147 clusters were investigated at different substrate temperatures. We found that the substrate temperature had a significant effect on the Cn147 cluster. For smaller Cu13 and Cu55 clusters, the substrate temperature in the range of study appeared to have little effect on the mean center-of-mass height. The clusters showed better degrees of epitaxy at 800 K. With the same substrate temperature, the Cu55 cluster demonstrated the highest degree of epitaxy, followed by Cu147 and then Cu13 clusters. In addition, the Cu55 cluster showed the lowest mean center-of-mass height. These results suggested that the Cu55 cluster is a better choice for the thin-film formation among the clusters considered. Our studies may provide insight into the formation of desired Cu thin films on a Si substrate.
