A TEM study of ZnO layers deposited by MBE and RF magnetron sputtering

The structure of MBE-grown ZnO layers was investigated along with RF sputtered layers at around 600 ∘C followed by a higher temperature anneal. The ZnO layers were either deposited directly on sapphire or on top of a GaN template. After the MBE growth on (0001)GaN, the analysed layers contain a large density of defects and the interface is not completely coherent on some 2-3 monolayers. In the case of RF sputtering, the samples comprised an Mn-doped part towards the surface on top of about a 150 nm pure ZnO layer. They exhibit a columnar structure and the adjacent domains are rotated from one another up to 90∘, putting [101¯0] and [11¯20] directions parallel. At high Mn concentration this columnar structure is blurred by the formation of Mn-rich precipitates for which we report on the structure, composition and crystallographic relationships with the surrounding matrix.