Pt Thin Films with Nanometer-Sized Terraces of (100) Orientation

Pulsed laser deposition was used to grow thin layers of Pt on (001)-oriented MgO substrate. The deposition temperature was varied from -25 to 600 degrees C, and the film thickness was varied from ca. 7 to 45 nm. The crystalline quality, orientation, and epitaxial relationship of Pt thin films on (001)-oriented MgO substrate were investigated by atomic force microscopy and X-ray diffraction as well,as through electrochemical probe reactions that are sensitive to the surface crystallographic orientations (H adsorption/desorption) and the width of the (100) terrace (NH3 electro-oxidation reaction). All thin (7 nm thick) Pt films exhibit only one diffraction peak (the (001) peak) and a 4 fold in-plane symmetry, indicating epitaxial growth is achieved independently of the deposition temperature. Moreover, the pole figure indicates that all films exhibit a Pt(001)[010]// [010] (001)MgO cube-on-cube epitaxial relationship, which is consistent with the AFM images. The films are prepared with nearly 60% of (100) sites, and the maximum width of the (100) terraces is nine atomic rows, attained at 325 degrees C.