A lowenergy electron diffraction investigation of the surface deformation induced by misfit dislocations in thin MgO films grown on Fe (001) The deposition of MgO on the Fe͑001͒ surface at room temperature and at elevated temperatures has been carried out using molecular beam epitaxy ͑MBE͒. MgO is observed to grow epitaxially with a 45°rotation between the Fe͑001͒ and MgO͑001͒ unit cell axes. The growth mode has been studied as a function of temperature using reflection high-energy electron diffraction ͑RHEED͒, while the chemical and structural characteristics of the MgO film have been studied using Auger electron spectroscopy and high resolution electron microscopy. The relaxation of the in-plane lattice parameter during growth at room temperature has been measured in situ using RHEED and ex situ using glancing incidence x-ray diffraction and during growth at elevated temperatures by means of RHEED. Pseudomorphic growth is observed up to a thickness of 4-5 monolayers, after which the in-plane lattice parameter starts to evolve towards the MgO bulk parameter as 1/2͗011͘ misfit dislocations are introduced at the Fe/MgO interface. The degree of relaxation as a function of epilayer thickness is compared with that expected for an equilibrium dislocation spacing in an array of dislocations of alternating orientation, and with that predicted by Freund's criterion for the blocking of a threading segment by an orthogonal misfit dislocation ͓J. Appl. Phys. 68, 2073 ͑1990͔͒.
The elastic deformation of the surface of thin MgO films grown on Fe(001) induced by the presence of misfit dislocations at the Fe/MgO interface has been put into evidence using low-energy electron diffraction. Satellite spots surrounding the fundamental Bragg reflections appear once the critical thickness is exceeded and undergo a shift in position as thickness of MgO increases, gradually blending in with the fundamental reflections. The evolution of the position of the spots is in good agreement with kinematical diffraction calculations in which the surface deformation is determined from the displacement field of a single misfit dislocation using both isotropic and anisotropic elasticity theory.
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