Ion beam assisted deposition of textured magnesium oxide templates on un-buffered glass and silicon substrates

Biaxially textured magnesium oxide (MgO) templates of 10-nm thickness were successfully fabricated on glass and silicon substrates without any buffer layers using Ar⁺ ion beam assisted e-beam evaporation. With an additional layer of 100 nm homoepi MgO on top, the in-plane misorientation of ∼6.5° and out-of-plane misorientation of ∼2.0° have been obtained. Prior to growth, the substrates were bombarded with the same Ar⁺ ion beam for a certain period ranging from 5 to 35 min to provide initial substrate conditions for textured MgO formation. The ion beam induced modification of the substrate surface morphology was characterized using atomic force microscopy. Reduced surface roughness R_a from 2 to 3 nm on the original glass substrates to below 1.0 nm after 5 min ion beam bombardment was found to be an important condition for the textured MgO formation. The nearly unchanged R_a ≤ 1 nm of the silicon substrate after the ion beam bombardment, however, suggests that additional surface modification is required for the textured MgO to form.