Dresden 2014 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 49: Atomic Layer Deposition

DS 49.8: Vortrag

Freitag, 4. April 2014, 11:45–12:00, CHE 91

Simulation of the deposition and growth of nano-crystalline MgF2 films via the low-temperature atom beam deposition method — Sridhar Neelamraju, •Johann Christian Schön, and Martin Jansen — MPI for Solid State Research, D-70569 Stuttgart

We model the deposition of magnesium difluoride (MgF2) clusters on a sapphire substrate and the subsequent growth of ordered MgF2-phases via the low-temperature atom beam deposition method. For the modeling procedure we use empirical potentials to describe the interactions within the substrate and the MgF2 deposit, and between the deposited atoms and the substrate. First, we established that primarily MgF2- and Mg2F4-clusters form in the gas phase, and thus the deposition could be described by the adsorption of such molecules on the substrate at low temperatures [1]. Next, the deposited MgF2-layers are annealed, and the structure of the resulting amorphous and nano-crystalline compounds is analyzed and compared with the results (pair distribution functions) of the experimental deposition [2]. We show that the appearance of an (at standard conditions) kinetically unstable CaCl2-type phase in the experiment [3] is due to the concurrent existence of a nano-crystalline CdI2-type modification of MgF2 predicted in earlier theoretical studies [4].

[1] S. Neelamraju et al., J. Chem. Phys. 137:194319 (2012); S. Neelamraju et al., Phys. Chem. Chem. Phys. 14:1223 (2012) [2] X. Mu et al., J. Appl. Cryst. 46:1105 (2013) [3] A. Bach et al., Inorg. Chem. 50:1563 (2011) [4] M.A.C. Wevers et al., J. Solid State Chem. 136:223 (1998)