POSSIBILITY OF THE METASTABLE Al3Si PHASE FORMATION IN COMPOSITE Al-Si FILMS OBTAINED BY ION-BEAM AND MAGNETRON SPUTTERING
Abstract
This article describes the peculiarities of the phase composition and the electronic structure of composite Al0.75Si0.25 films on a silicon substrate Si(100) obtained by magnetron and ion-beam sputtering. As a result of magnetron sputtering, Si nanocrystals with the sizes of ~25nm and metastable ordered solid solution Al3Si are formed in an Al matrix. Al3Si is characterized by a Рm3m cubic crystal structure with a primitive cell parameter a = 4.085Å. The films obtained by ion-beam sputtering contain only the ordered solid solution Al3Si.
The Al3Si phase formation is accompanied by changes of the Al 3s-states density distribution. There is a linear dependence of the density-of-states distribution from energy instead of a parabolic dependence in the lower and middle part of the valence band (as in the case of pure metal). A similar effect was observed for Si 3s-states.
In addition, the interaction between Al and Si atoms leads to the decrease of Al 3s-states density near the Fermi level. This is a result of electrons transitioning from Al atoms to the more electronegative silicon atoms.
In case of magnetron films, selective etching of aluminium leads to the formation of nanoporous sponge structure. And the selective etching of ion-beam films does not cause well-developed morphology formation.
Subsequent pulsed photon annealing (PPA) of the ion-beam films (at 145-216 J/cm2) leads to the partial disintegration of Al3Si phase with the formation of metallic aluminium and silicon nanocrystals. The size of Si nanoparticles depends on PPA regimen and equals to 50-100 nm. Subsequent etching of the sample subjected to PPA leads to the formation of a nanoporous structure.
ACKNOWLEDGMENTS
The work was supported by the Ministry of Education and Science of the Russian Federation in the framework of the state order to higher education institutions in the sphere of scientific research for years 2017 - -2019. Project No. 3.6263.2017/VU.
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