Epitaxial growth of Pt on basal-plane sapphire: a seed film for artificially layered magnetic metal structures

The epitaxial growth of Pt on basal-plane sapphire, i.e. sapphire (0001), by molecular beam epitaxy is described. Growth is monitored in situ using X-ray photoelectron diffraction (XPD), reflection high energy electron diffraction (RHEED) and low energy electron diffraction (LEED). The structural perfection of thin ( < 250 Å) films of Pt is studied using X-ray diffraction and electron microscopy. We find that Pt nucleates on the sapphire surface at 600°C as islands which are rotationally twinned about the Pt[111] axis. The epitaxial relationship is: Pt[111]‖Al 2O 3[0001] and Pt(110)‖Al 2O 3 (101̄0). Island coalescence occurs at a thickness of $ ̃ 15 Å and X-ray diffraction shows that the Pt films have a high structural perfection. Such films are nearly ideal as seed films for a variety of epitaxial magnetic multilayers and alloys.