Fabrication and magnetic properties of prepatterned epitaxial nanodots

Abstract

Nanoscale pillar structures have been fabricated from semiconductor materials using reactive ion etching with gold colloids as etch masks. Different metallic multilayer systems including ferromagnetic metals have been grown on these structures using molecular beam epitaxy. This yields nanoscale circular magnetic dots on top of the pillars and an antidot arrangement for the continuous film in the trenches between the pillars. The growth modes of these systems have been investigated using scanning electron microscopy and scanning transmission electron microscopy including electron energy loss spectroscopy. It is established that there is no exchange interaction between the magnetic material on top of the pillars and in the trenches. Furthermore the magnetic material on top of the pillars grows with the same epitaxy as the continuous film in the trenches indicating that there is the same crystallographically well-defined surface on top of the pillars as in the trenches. The magnetic properties have been investigated using specially adapted magneto-optical Kerr effect. It has been found that the magnetic dots on top of the pillars exhibit the same angular dependence of the anisotropy as the magnetic film in the trenches. This strong angular dependence together with the size of the switching field is indicative of single domain structures with reversal via coherent rotation.