The atomically smooth SrTiO(3) (100) with steps one unit cell in height was obtained by treating the crystal surface with a pH-controlled NH(4)F-HF solution. The homoepitaxy of SrTiO(3) film on the crystal surface proceeds in a perfect layer-by-layer mode as verified by reflection high-energy electron diffraction and atomic force microscopy. Ion scattering spectroscopy revealed that the TiO(2) atomic plane terminated the as-treated clean surface and that the terminating atomic layer could be tuned to the SrO atomic plane by homooepitaxial growth. This technology provides a well-defined substrate surface for atomically regulated epitaxial growth of such perovskite oxide films as YBa(2)Cu(3)O(7-delta).

The atomically ultrasmooth surfaces with atomic steps of sapphire substrates were obtained by annealing in air at temperatures between 1000 and 1400 °C. The terrace width and atomic step height of the ultrasmooth surfaces were controlled on an atomic scale by changing the annealing conditions and the crystallographic surface of substrates. The obtained ultrasmooth surface was stable in air. The topmost atomic structure of the terrace was examined quantitatively by atomic force microscopy and ion scattering spectroscopy as well as a theoretical approach using molecular dynamics simulations.

We have identified the surface polar structure of wurtzite-type ZnO films by coaxial impact-collision ion scattering spectroscopy. High-quality ZnO epitaxial films were prepared on sapphire (␣-Al 2 O 3 ) ͑0001͒ substrates by laser molecular beam epitaxy using a ZnO ceramic target. The ͑0001͒ crystallographic plane ͑the O face͒ was found to terminate the top surface of the ZnO film by comparing spectra of the films with those of well-defined ͑0001͒ and ͑0001͒ surfaces of bulk single crystals. The preferential ͓0001͔ growth direction of ZnO films is discussed from the viewpoints of the chemical interaction at the interface and surface stability against sublimation.

A perovskite single-crystal substrate, NdGaO3 (001), was thermally annealed in air to give an atomically defined surface structure. From analysis with coaxial impact-collision ion scattering spectroscopy, the terminating atomic layer was identified to be NdO1+δ , i.e., the A-site oxide monolayer in perovskite ABO3. This result is contrary to the B-site oxide (BO2−δ) termination observed in other perovskite surfaces, such as wet etched SrTiO3 and LaAlO3 or annealed (LaAlO3)0.3–(Sr2AlTaO6)0.7 (LSAT).

Growth and characterization of N-polar GaN films on SiC by metal organic chemical vapor deposition J. Appl. Phys.Nondestructive determination of the polarity of GaN has been achieved by the use of coaxial impact-collision ion scattering spectroscopy analysis. The polarity of a GaN film with a smooth surface on non-nitrided c-plane sapphire was identified ͑0001͒ ͑Ga face; ϩc͒. GaN films with a 20 nm buffer layer on nitrided sapphire had (0001 ) ͑N face; Ϫc͒ polarity and a hexagonal faceted surface. The influence of both the buffer layer and of substrate nitridation on the polarity of wurtzite ͕0001͖ GaN films deposited by two-step metal organic chemical vapor deposition ͑MOCVD͒ has been investigated. The polarity of the buffer layer on a nitrided sapphire substrate was altered by varying its thickness or the annealing time. It was found that the polarity of the GaN film is determined by the polarity of the annealed buffer layer; MOCVD-GaN films on buffer layers with ϩc and Ϫc polarity have either ϩc ͑smooth surface͒ or Ϫc ͑hexagonal facet͒ polarity, respectively.