From the Very First Stages of Mn Deposition on Ge(001) to Phase Segregation

Abstract

In this work, we have combined scanning tunneling microscopy (STM) with highresolution transmission electron microscopy (HR-TEM) to investigate the initial stages of Mn deposition on Ge(001) surfaces. The growth temperature has been chosen to be (353 ± 5) K, which is typical for the synthesis of Ge 1−x Mn x thin films. At the early stage of the Mn deposition, two distinct kinds of islands are observed even for Mn coverage much smaller than a monolayer with an average size of respectively 1-2 nm and 4-5 nm. Small islands were found to nucleate in the hollow between the Ge dimer rows and they were formed by consuming Ge from two adjacent rows. This indicates that Mn-Ge alloying has been taken place even at the early stage of the Mn deposition. When the Mn coverage increases, coarsening between small islands with newly deposited ad-atoms occurs, giving rise to the formation of monosized islands. Interestingly, these nanostructures have an average size of 4-5 nm and separated by a spacing of 7-8 nm that are similar to the spatial ordering of nanocolumns resulting from spinodal decomposition in (Ge,Mn) thin films. HR-TEM analyses indicate that those 1 nanoislands are epitaxial, defect free and perfectly coherent with the Ge substrate. A subsequent anneal will result in the formation of Mn 5 Ge 3 islands.

Self-Assembly of GeMn Nanocolumns in GeMn Thin Films

“…After the first report of ferromagnetism in the Ge 1 − x Mn x system with T C = ~116 K [16], the synthesis of Ge 1 − x Mn x DMSs has been the subject of numerous investigations [26][27][28][29][30][31][32][33][34][35][36]. Since it has been shown in Ref.…”

Influence of fabrication parameters on the magnetic and structural properties of Mn5Ge3

“…Moreover, the full control of the magnetic easy axis by using different annealing procedure could help to improve the spin polarization efficiency in spintronic devices. Up to now, by using conventional SPE, Mn 5 Ge 3 on Ge (001) generally grows in the form of nano-islands due to energy-unfavorable growth of the (001) Mn5Ge3 /(001) Ge interface and inevitable segregation of Mn on the Ge (001) substrates during the annealing process [12][13][14][15]. To avoid the formation of nano-islands of Mn 5 Ge 3 on Ge (001), the ultrafast-SPE was used to modify the kinematic and thermodynamic process during annealing in this work.…”