Hirofumi Fukumoto

Heteroepitaxial growth of Y2O3 films on silicon

Yttria (Y2 O3 ) films have been grown on Si (100) and Si (111) substrates heated at 800 °C by vacuum evaporation. X‐ray diffraction and reflection high‐energy electron diffraction observations reveal the heteroepitaxial growth of Y2 O3 films on Si (100) and Si (111) substrates. The (111) oriented Y2 O3 films are grown directly on Si (111) substrates. The (100) oriented Y2 O3 films are grown on the thin (Y2 O3 )0.09 (ZrO2 )0.91 layer predeposited on Si (100) substrates instead of direct growth on Si (100) substrates.

Heteroepitaxial growth of Y/sub 2/O/sub 3/ films on silicon

Yttria (Y2 O3 ) films have been grown on Si (100) and Si (111) substrates heated at 800 °C by vacuum evaporation. X‐ray diffraction and reflection high‐energy electron diffraction observations reveal the heteroepitaxial growth of Y2 O3 films on Si (100) and Si (111) substrates. The (111) oriented Y2 O3 films are grown directly on Si (111) substrates. The (100) oriented Y2 O3 films are grown on the thin (Y2 O3 )0.09 (ZrO2 )0.91 layer predeposited on Si (100) substrates instead of direct growth on Si (100) substrates.

Growth of crystalline zirconium dioxide films on silicon

Zirconium dioxide (ZrO2) films have been grown on Si(100), Si(111), and SiO2/Si substrates heated at the range from room temperature to 800 °C by vacuum evaporation. X‐ray diffraction and reflection high‐energy electron diffraction observations reveal the epitaxial growth of tetragonal ZrO2(200) films on Si(100) substrates at 800 °C. The epitaxial imperfection is caused by preferentially oriented tetragonal ZrO2(002) grains. The crystalline system of ZrO2 films depends on the substrate temperature. The crystalline perfection and the orientation of tetragonal ZrO2 films grown at 800 °C depend on the substrate orientation.

Heteroepitaxial Growth of Yttria-Stabilized Zirconia (YSZ) on Silicon

Yttria-stabilized zirconia (YSZ) films have been grown on Si(100) substrates heated at 800°C by vacuum evaporation. X-ray diffraction and reflection high-energy electron diffraction observations reveal the heteroepitaxial growth of cubic YSZ (200) films on Si(100) substrates. The reflection high-energy electron diffraction of the films show that the and directions in the plane of cubic YSZ nearly coincide with the and directions of the Si substrate, respectively. Accordingly, (200)-oriented cubic YSZ could be exactly (<1%) lattice-matched to (100)-oriented Si substrates.

Electrical characteristics of metal‐insulator‐semiconductor diodes with ZrO2/SiO2 dielectric films

Thin films of ZrO2 vacuum‐deposited on Si(100) substrates were oxidized in dry O2 at 800 °C and then analyzed by infrared absorption and Auger electron spectroscopy. It was found that the SiO2 layer was formed at the ZrO2/Si interface. Mo/ZrO2/SiO2/p‐Si(100) metal‐insulator‐semiconductor diodes were electrically characterized. The static dielectric constant of the ZrO2 layer decreases from 21.1 e0 to about 15.5 e0 due to the crystallization of amorphous ZrO2 during the oxidation. The SiO2 layer formed at the ZrO2/Si interface was found to lower the leakage current through the dielectric film.

As-Grown Preparation of Superconducting Epitaxial Ba2YCu3Ox Thin Films Sputtered on Epitaxially Grown ZrO2/Si(100)

High-Tc superconducting Ba2YCu3Ox thin films have been epitaxially grown on Si(100) substrates with the epitaxially grown tetragonal ZrO2 or cubic yttria-stabilized zirconia (YSZ) as a buffer layer. The thin films were prepared by rf magnetron sputtering of the stoichiometric Ba2YCu3Ox target below 700°C. An adequate positive substrate bias was necessary to ensure surface smoothness and to show the superconducting transition above liquid nitrogen temperature without any post-treatment. The highest Tc(onset) and Tc(end) observed were 88 K and 84 K, respectively.

Strain measurements in heteroepitaxial yttria‐stabilized zirconia on Si by ion beam channeling

Yttria‐stabilized zirconia (YSZ) films have been epitaxially grown on Si(100) substrates at 800 °C by vacuum evaporation. By post‐annealing in dry O2 at 800 °C, SiO2 layer was formed at the YSZ/Si interface. Strain in heteroepitaxial cubic YSZ films has been measured by ion beam channeling. The strain was found to be tensile. This tensile strain is caused as the sample is cooled down after growth due to the difference in thermal expansion coefficients between YSZ and Si. The tensile strain is increased by annealing in dry O2, due to the SiO2 layer formed at the YSZ/Si interface. The tensile strain is also introduced in the near‐interface region of Si substrate under SiO2.

Evaluation of crystalline quality of heteroepitaxial yttria-stabilized zirconia films on silicon by means of ion beam channeling

Yttria‐stabilized zirconia (YSZ) films have been deposited by vacuum evaporation on Si(100) substrates heated at 800 °C. Rutherford backscattering spectra of the YSZ films show that they are epitaxially grown on the Si(100) substrate, which is consistent with x‐ray diffraction and reflection high‐energy electron diffraction observations. The spread of crystallite orientation in the epitaxial film is estimated to be 0.22°, by analyzing the angular dependence of the total backscattering yield. The dominant defect is suggested to be a stacking fault by dechanneling ion energy dependence measurements and 30% of the oxygen atoms are displaced from the oxygen sublattice site.

Structural Changes of Amorphous GeTe2 Films by Annealing (Formation of Metastable Crystalline GeTe2 Films)

Amorphous GeTe 2 films with the thickness ∼ 0.5 µm, prepared by sputtering technique, transform into the crystalline GeTe 2 films with the isomorphic structure to β-cristobalite, cubic SiO 2 , at T a (annealing temperature)=200°C. The cubic phase of GeTe 2 is metastable and decomposes into the mixed crystal of GeTe and Te at T a =250°C.

Characterization of epitaxial yttria‐stabilized zirconia/Si interface by ion beam channeling

Yttria‐stabilized zirconia (YSZ) films which have high crystalline quality and no dislocation near the YSZ/Si interface, have been epitaxially grown on Si(100) in spite of the relatively large lattice mismatch between YSZ and Si. The formation of the SiO2 layer at the YSZ/Si interface during the YSZ deposition takes an important part as a buffer layer in the epitaxial growth of YSZ films on Si.