A study of growth and the relaxation of elastic strain in MgO on Fe(001)

Abstract

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.

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

“…Additionally, the dislocation lines exhibit a deviating electronic structure due to a lower amount of interfacial coupling, which also contributes to the image contrast. Similar dislocation networks have been observed for NiO on Pd(001) 206 and MgO on FeO(001) 207,208 via STM and for MgO, 209 NiO, 142 and CoO …”

Enhanced magnetoresistance by monoatomic roughness in epitaxial Fe/MgO/Fe tunnel junctions

“…This growth is known to be layer by layer with a lattice spacing mismatch: a MgO / √ 2 a Fe = 1.036. In that case, as usually observed [30], two growth regimes can be distinguished, as indicated by the vertical arrow. For a deposited MgO thickness less than 5 ML (as evaluated by the intensity oscillations), the growth is so-called pseudomorphic, that is, the deposited layers are strained by the buffer and the lattice parameter is almost constant [ Fig.…”

Preparation of nanometer-scale iron dots on insulating layer

“…This technique has already been studied in the case of Fe/MgO systems and good quality of the layers was demonstrated [21]. All our samples were prepared on MgO (001) substrates.…”

“…On the other hand, the lattice mismatch between Fe and MgO is only A Fe layer with a nominal thickness of 1 nm was deposited on top of this polycrystalline layer, so that the final structure of the samples is: (Fe, 1 nm/Au, 50 nm/Fe, 10 nm/MgO, 0.8 nm/Fe, 1 nm). Due to the large surface energy difference between Fe (2.9 J/m 2 ) and MgO (1.16 J/m 2 ) [21], 3D Volmer-Weber growth occurred. The mean diameter of the iron particles determined from the STM image ( Fig.…”