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Article Dans Une Revue Physical Review B: Condensed Matter and Materials Physics (1998-2015) Année : 2009

Phase transition and surface morphology of MnAs/GaAs(001) studied with in situ variable-temperature scanning tunneling microscopy

Résumé

The MnAs phase transition from the hexagonal ferromagnetic alpha to the orthorhombic paramagnetic beta phase has been investigated in situ by variable-temperature scanning tunneling microscopy (STM) as a function of epilayer thickness. The alpha-beta phase coexistence leads to the formation of a self-organized stripes pattern of alternating alpha and beta regions. The morphology evolution of the alpha-beta periodic array of domains has been imaged in detail. The period and corrugation of this pattern are linear functions of the epilayer thickness with a domain periodicity nearly five times larger than film thickness. Also, STM local imaging through the phase-coexistence region (10-45 degrees C) shows unambiguously the absence of mass transport during the transition. The self-organization of alpha-beta stripes is consistent with an elastic-energy equilibrium state of the heteroepitaxial system at each temperature, as previously proposed for the origin of the modulated structure [V. M. Kaganer et al., Phys. Rev. B 66, 045305 (2002)]. Independently of self-organized alpha-beta regions, the surface displays anisotropic mounds that are elongated along MnAs a axis. This facetting process leads to a peculiar, highly anisotropic surface with oriented facets and submicron periodic modulation along the hexagonal c axis. Smoother surfaces with larger terraces are obtained following postgrowth annealing. These results suggest that a careful control of the growth temperature and annealing procedure can be used to tailor the surface morphology for specific applications requiring anisotropic templates.
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hal-01240964 , version 1 (09-12-2015)

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R. Breitwieser, Franck Vidal, I. L. Graff, Massimiliano Marangolo, Mahmoud Eddrief, et al.. Phase transition and surface morphology of MnAs/GaAs(001) studied with in situ variable-temperature scanning tunneling microscopy. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2009, 80 (4), pp.045403. ⟨10.1103/PhysRevB.80.045403⟩. ⟨hal-01240964⟩
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