Co2TiSi films were grown by molecular beam epitaxy on GaAs(001) and analyzed using reflection high-energy electron diffraction, and electron microscopy. In addition, X-ray diffraction was combined with lattice parameter calculations by density functional theory comparing the \textit{L21} and \textit{B}2 structures and considering the influence of non--stoichiometry. Columnar growth is found and attributed to inhomogeneous epitaxial strain from non-random alloying. In films with thicknesses up to 13~nm these columns may be the origin of perpendicular magnetization with the easy axis perpendicular to the sample surface. We found \textit{L21} and \textit{B}2 ordered regions, however the [Co]/[Ti]--ratio is changing in dependence of the position in the film. The resulting columnar structure is leading to anisotropic \textit{B}2--ordering with the best order parallel to the axes of the columns.
@article{arxiv.1907.05238,
title = {Structural properties of Co$_{2}$TiSi films on GaAs(001)},
author = {B Jenichen and J Herfort and M Hanke and U Jahn and X Kong and M T Dau and A Trampert and H Kirmse and S C Erwin},
journal= {arXiv preprint arXiv:1907.05238},
year = {2019}
}