Temperature dependence of the epitaxial growth of Pt on basal-plane sapphire

We have investigated the temperature-dependent growth characteristics of epitaxial Pt(111) on Al2O3(0001) using in-situ scanning tunneling microscopy. For temperatures near the onset of epitaxy (600°C), the Pt films grown by ion-beam sputtering, are flat and well-ordered. With increasing substrate deposition temperature, the surfaces grow rougher and at 700°C display island-on-island growth with up to 12 monosteps visible. When subjected to a post-deposition anneal of 950°C, the Pt becomes very smooth and the initial growth temperature becomes less important. Finally, we show that the Pt provides an excellent seed layer on which to grow and investigate metals such as Co and Cu.