B. S. Kwak

Metalorganic chemical vapor deposition of PbTiO3 thin films

PbTiO3 thin films have been grown successfully for the first time by using purely metalorganic precursors, namely, titanium isopropoxide and tetraethyllead. A scanning electron micrograph showed dense and noncolumnar growth with good surface morphology. Temperature‐dependent x‐ray diffraction studies provide evidences for a reversible tetragonal to cubic phase transition around 540 °C. At room temperature, the dielectric constant is about 180.

Metalorganic chemical vapor deposition of BaTiO3 thin films

We report the results of a recent study on the {ital in} {ital situ} deposition of single phase BaTiO{sub 3} thin films by using the metalorganic chemical vapor deposition technique. The effects of growth parameters on the characteristics of the thin films were investigated in the substrate temperature range of 550--800 {degree}C. Barium {beta}-diketonate and titanium isopropoxide were used as the metal sources. Growth rates ranging from submicron to several microns per hour have been deposited on various substrates in an inverted vertical warm-wall reactor. X-ray diffraction data and Rutherford backscattering spectra provided the evidence for single BaTiO{sub 3} phase. Scanning electron microscopy was used to study the surface and the cross-sectional morphology of the films. Dielectric constant of the as-deposited film was around 250 at room temperature. The resistivity of the films were greater than 10{sup 9} {Omega} cm.

Metalorganic chemical vapor deposition of [100] textured MgO thin films

We report on the results of a recent study on the deposition of [100] textured MgO films on fused quartz substrates by using the metalorganic chemical vapor deposition technique. Magnesium β‐diketonate was used as the metal source and the growth rate of the film was about 0.4 μm/h at 740 °C in a horizontal warm wall reactor. X‐ray diffraction experiments provided evidence that the MgO films on fused quartz were fully textured with [100] orientation perpendicular to the substrate surface. The films had a very smooth surface morphology and optical transparency with an index of refraction of 1.71.

c‐axis oriented YBa2Cu3O7−x superconducting films by metalorganic chemical vapor deposition

Highly textured single phase superconducting YBa2Cu3O7−x films have been successfully grown on the yttria‐stabilized zirconia (100) substrates by using the metalorganic chemical vapor deposition technique. The as‐deposited films grown at 650 °C were homogeneous mixtures of the related metal oxides and carbonates. Subsequent thermal annealing under oxygen flow yielded single phase superconducting films whose thickness corresponded to the deposition rates of approximately 10 μm/h. After the post‐annealing the films deposited on the yttria‐stabilized zirconia substrates exhibited a highly textured x‐ray pattern with c axis perpendicular to the substrate surface. These films show an onset superconducting transition temperature of 93 K with the resistance becoming zero at 84 K.

Metalorganic chemical vapor deposition of Tl2CaBa2Cu2Oy superconducting thin films on sapphire

Superconducting Tl2CaBa2Cu2Oy thin films have been successfully grown on the single‐crystal sapphire (1102) substrate by using the metalorganic chemical vapor deposition technique. The growth rate of the films was about 5 μm/h. The as‐deposited film was post‐annealed in a partially sealed ceramic crucible in the presence of a Tl2Ca2Ba2Cu3Oy pellet to achieve the superconducting phase. The x‐ray data show strong diffraction from the Tl2CaBa2Cu2Oy superconducting phase in addition to the trace amounts of Ca2CuO3 and BaCO3. Superconducting transition temperatures with onset above 100 K and zero resistance at 94 K can be obtained by further heat treatment at 500 °C in oxygen.

Metalorganic chemical vapor deposition of Tl sub 2 CaBa sub 2 Cu sub 2 O sub y superconducting thin films on sapphire

Superconducting Tl2CaBa2Cu2Oy thin films have been successfully grown on the single‐crystal sapphire (1102) substrate by using the metalorganic chemical vapor deposition technique. The growth rate of the films was about 5 μm/h. The as‐deposited film was post‐annealed in a partially sealed ceramic crucible in the presence of a Tl2Ca2Ba2Cu3Oy pellet to achieve the superconducting phase. The x‐ray data show strong diffraction from the Tl2CaBa2Cu2Oy superconducting phase in addition to the trace amounts of Ca2CuO3 and BaCO3. Superconducting transition temperatures with onset above 100 K and zero resistance at 94 K can be obtained by further heat treatment at 500 °C in oxygen.

Difference Raman spectra of PbTiO3 thin films grown by metalorganic chemical vapor deposition

The technique of Raman scattering has been used to investigate the properties of ferroelectric PbTiO3 thin films grown on both single‐crystal KTaO3 and fused quartz substrates by means of metalorganic chemical vapor deposition. The ‘‘difference Raman’’ technique was employed in which substrate contributions were subtracted in order to obtain Raman spectra for the PbTiO3 films. A comparison of the Raman spectra taken at 300 and 80 K for PbTiO3 and KTaO3 reveals two different types of temperature behavior and these effects are accounted for by the soft‐mode theory.

Epitaxial lead zirconate‐titanate thin films on sapphire

Pb(Zr1−xTix)O3 thin films covering the whole compositional range x=0 to x=1 have been grown for the first time on the sapphire (1102) plane using the metalorganic chemical vapor deposition technique. The films are three‐dimensionally epitaxial and exhibit single crystal properties. The structural transitions, examined by x‐ray diffraction, are shifted slightly from the bulk single crystal values. Ferroelectric P‐E hysteresis curves and the dielectric constant of the films were investigated using interdigitated electrodes fabricated by photolithography.

Difference Raman spectra of PbTiO[sub 3] thin films grown by metalorganic chemical vapor deposition

The technique of Raman scattering has been used to investigate the properties of ferroelectric PbTiO3 thin films grown on both single‐crystal KTaO3 and fused quartz substrates by means of metalorganic chemical vapor deposition. The ‘‘difference Raman’’ technique was employed in which substrate contributions were subtracted in order to obtain Raman spectra for the PbTiO3 films. A comparison of the Raman spectra taken at 300 and 80 K for PbTiO3 and KTaO3 reveals two different types of temperature behavior and these effects are accounted for by the soft‐mode theory.

Raman scattering and x‐ray diffraction investigations of highly textured (Pb1−xLax)TiO3 thin films

Highly textured lead lanthanum titanate (PLT) thin films grown on Si(100) substrates by the metalorganic chemical vapor deposition technique are characterized using x‐ray diffraction (XRD), Raman spectroscopy, and energy‐dispersive x‐ray analysis. The texturing consisted of an alignment of the {100} crystallographic axes of the film perpendicular to the Si substrate. The tetragonality of the films was found to decrease as the lanthanum concentration increased. Raman spectra exhibited features characteristic of bulk PLT, including the observation of the soft mode. Variations of the phonon modes for PLT have been investigated as a function of La concentration and sample temperature.