Existence and atomic arrangement of microtwins in hexagonal MnAs ferromagnetic epilayers grown on GaAs (100) substrates with monolayer InAs Buffers

Abstract

Selected-area electron-diffraction pattern (SADP) and high-resolution transmission electron microscopy (HRTEM) measurements were carried out to investigate the existence and the atomic arrangement of microtwins in hexagonal MnAs ferromagnetic epilayers grown on GaAs (100) substrates with monolayer InAs buffer layers by using molecular beam epitaxy. The magnetization curve as a function of the magnetic field at 5 K showed that the MnAs thin films were ferromagnetic, and the magnetization curve as a function of the temperature revealed that the ferromagnetic transition temperature was as high as 325 K. The SADP and HRTEM results showed that an epitaxial relationship was formed among the hexagonal MnAs layer, the InAs layer, and the zincblende GaAs substrate. Microtwins existed between the MnAs grain boundaries on top of the InAs layers. Based on the SADP and HRTEM results, we present a possible atomic arrangement of the microtwins for the MnAs-InAs-GaAs heterostructure. (C) 2005 American Institute of Physics.