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Investigates the annealing effects of Y-Ba-Cu-O superconductor thin films. Ion implantation of the films; Microcrystal growth of the annealed films; Discussion on monitoring of the buildup of structural disorder in the film.

The preparation of La0.8Sr0.2MnO3 (LSMO) films on LaAlO3 (LAO) and SrTiO3 (STO) substrates was examined by an excimer laser MOD processes (ELMOD). Epitaxial LSMO films on the LAO substrate were obtained by the ArF laser irradiation at a fluence of 100 mJ/cm2 for 10, 30, 60 and 90 min with heating at 500 °C. In the case of the STO substrate with heating at 500 °C, epitaxial LSMO was obtained by the ArF laser irradiation at 70 mJ/cm2 whereas no film was formed at 100 mJ/cm2. The effects of the laser fluence, irradiation time and film thickness on the temperature dependence of the resistance and TCR (defined as 1/R·dR/DT) of the LSMO films on the LAO substrate were investigated. It was found that the resistance of the 80 nm thick LSMO film that was irradiated by the ArF laser at a fluence of 100 mJ/cm2 for 60 min showed a metallic temperature dependence from 310 to 100 K, and the maximum temperature coefficient of resistance of the film (TCR: defined as 1/R·dR/DT) was 3.4% at 265 K. In the case of the STO substrate, the resistance of the 80 nm thick LSMO film that was irradiated by the ArF laser at a fluence of 70 mJ/cm2 for 60 min showed a Tc at 280 K, and the maximum TCR of the film was 2.9% at 220 K. The formation mechanisms of the epitaxial LSMO films obtained by the ELMOD process also are discussed. [Copyright &y& Elsevier]

Time-resolved ion current measurements for laser ablation of Fe in nitrogen gas were performed. The current due to electrons, N, Fe ion and Fe neutral was observed at the substrate. At nitrogen pressures between 1 × 10−3 Torr and 1 × 10−1 Torr, the amount and the velocity of the Fe ion arriving at the substrate increased as the nitrogen pressure was increased. The velocity of the Fe ion was approximately 60 km/s and the maximum amount of it was estimated to be not more than 0.3 percent of the ejected Fe species. The Fe-N thin films prepared in this nitrogen pressure region showed the highest (200) orientation and increase of the crystallite size. It is considered that the Fe ion arriving at the substrate has the effect of enhancing the mobility of deposited species, resulting in the generation of the highest oriented Fe-N thin film composed of the largest crystallites. [ABSTRACT FROM AUTHOR]

Discusses the effect of copper concentration on the structure and microwave properties in yttrium barium copper oxide (YBCO) thin films. Composition and electrical properties of YBCO films; Epitaxial relationship between the film and substrate.

Semiconducting β-FeSi2 thin films were epitaxially as-grown on Si(111) substrates at a substrate temperature of 600 °C, which is at least 200 °C lower than ordinary annealing temperatures, by using the facing targets direct-current sputtering (FTDCS) method using an FeSi2 target without annealing. The deposited film exhibits a smooth surface with a surface roughness root mean square of 1.47 nm. The direct and indirect optical band gaps estimated from the experiment were in agreement with those of the single crystalline bulk. Temperature dependence of the electrical conductivity implied Co incorporation from the FeSi2 targets with a purity of 3N. The FTDCS method, in which a substrate is free of plasma and energetic neutral atoms diffused into the substrate owing to low Ar pressure sputtering, is effective for the direct epitaxial growth of β-FeSi2 thin films with smooth surfaces. [ABSTRACT FROM AUTHOR]

Various optical measurements confirm that optical absorption in uniform thin films made from nanocrystalline iron disilicide (nc-FeSi2) with a 3–5 nm radius is larger by about 10% than that of single crystalline β-FeSi2. It is also found that the hydrogenation of nc-FeSi2 changes strongly its optical characteristic energies. The nanocrystalline state appears characteristically in the imaginary part of dielectric constants of β-FeSi2 around 2–3 eV. [ABSTRACT FROM AUTHOR]

Ferromagnetic Fe3Si thin films with an extremely smoothsurface morphology can be epitaxially grown on Si(111) at roomtemperature by facing target direct-current sputtering. The epitaxial relationship is Fe3Si(111)‖Si(111) with Fe3Si[110]‖Si[110]. By the application of the extinction rule of x-ray diffraction, the generated Fe3Si was confirmed to possess a B2 structure and not a DO3 one. The film showed a saturation magnetization value of 960 emu/cm³, which was slightly lower than that of bulk DO3-Fe3Si. It was observed that the magnetization easy axis was along the [110] direction in the film plane [ABSTRACT FROM AUTHOR]

La0.8Sr0.2MnO3 (LSMO) films were prepared on LaAlO3 substrates by excimer laser metal organic deposition (ELMOD) at 500 °C. The temperature dependence of resistance of the LSMO films was investigated by changing the laser fluence, irradiation time, and film thickness. It was found that the resistance of the LSMO films 80 nm in thickness that were irradiated by an ArF laser at a fluence of 100 mJ/cm2 for 60 min showed a metallic temperature dependence, and the maximum temperature coefficient of resistance of the films (defined as 1/R×dR/dT) was 3.4% at 265 K. [ABSTRACT FROM AUTHOR]

Amorphous iron silicide was reported to be semiconducting as well as β-FeSi[sub 2], and it has received considerable attention from both the physical and engineering points of view. However, there have been few studies and its basic properties are still unknown. We could grow the semiconducting nanocrystalline iron disilicide thin films by pulsed-laser deposition using an FeSi[sub 2] target. They consist of crystallites with diameters ranging from 3 to 5 nm. The carrier density and the mobility at 300 K were 1.5×10[sup 19] cm[sup -3] and 35 cm/V s, respectively. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Variable-emittance radiators based on the metal—insulator transition of (La, Sr)MnO[sub 3] thin films have been developed. The emittance property of the films was evaluated from infrared reflectance spectra; that is, the (La, Sr)MnO[sub 3] thin films show low emittance at low temperature but high emittance at high temperature. Moreover, the emittance property significantly changes at the metal—insulator transition temperature, where the material changes from a highly reflective (i.e., low emissive) metal to a less reflective (i.e., high emissive) insulator. The (La, Sr)MnO[sub 3] thin films fitted on a spacecraft surface can, therefore, be used to automatically control the emissive heat transfer from the spacecraft without the need for any electrical power. The developed radiators also greatly reduce the weight and production cost of the thermal control devices. The dependence of the emittance property on film thickness reveals that 1500-nm-thick films can be used for variable-emittance radiators. [ABSTRACT FROM AUTHOR]

Examines the in-plane anisotropic transport properties in epitaxial Bi[sub 2](Sr,Ca)[sub 3]Cu[sub 2]O[sub x] films grown on tilted (001)SrTiO[sub 3] substrate. Observation on the substrate surface; Alignment of film b axis with incommensurate modulation; Resistivity of the transport along the a axis.

Studies the in situ epitaxial growth of Bi[sub 2](Sr,Ca)[sub 3]Cu[sub 2]O[sub x] films by ion beam sputtering on cleaved MgO substrates. Crystallographic structures; Symmetry of the epitaxial films; Types of equivalently misoriented domains; Epitaxial relationship between the domains and the cleaved substrates.

As-grown crystallized Bi2Sr2Ca1Cu2Ox phase films were prepared on MgO(100) substrates by rf magnetron sputtering. The as-grown film showed the Tc onset of 92 K and the Tc end of 82 K. By annealing in the furnace at 480 °C after deposition, superconducting property and the c-axis lattice constant varied with atmosphere during annealing. The film after annealing in air at 480 °C exhibited the highest superconducting transition with the Tc onset of 93 K and the Tc end of 85 K. The Tc onset increased when the c-axis lattice constant was increased, suggesting that the Tc onset increases with decreasing the oxygen content of the film. [ABSTRACT FROM AUTHOR]

Superconducting Bi-Sr-Ca-Cu-O thin films have been prepared on (100) MgO substrates at about 600 °C by coevaporation. The c-axis lattice constant of this system was controlled to the values of 24–43 Å by changing film composition. Superconducting transition temperatures of these films were affected by substrate temperature and by a post-deposition annealing at a low temperature. The highest zero resistance temperature (Tc, zero) of the as-grown Bi2(Sr,Ca)3Cu2Ox film was 79 K. The best Bi2(Sr, Ca)4Cu3Ox film showed an onset temperature of 105 K and Tc, zero zero of 78 K after annealing at 400 °C for 1 h. [ABSTRACT FROM AUTHOR]

Thin film with a high Tc single phase was prepared on a (100)MgO substrate at a substrate temperature of about 620 °C by coevaporation of Bi2O3, Sr, Ca, and Cu metal. The resistive superconducting transition with onset Tc of 80 K was observed for this film. By post-deposition annealing at 850 °C, the high Tc phase was transformed into a low Tc phase, while films annealed at a higher temperature such as 890 °C maintained the high Tc phase. These results indicated that the high Tc phase can exist only at the high-temperature region (∼890 °C) while the stable phase existing at the low-temperature region (∼850 °C) is the low Tc phase. [ABSTRACT FROM AUTHOR]

Epitaxial films of Y-Ba-Cu-O were obtained on a Si substrate, using an epitaxial intermediate layer consisting of BaTiO3(or SrTiO3)/MgAl2O4. MgAl2O4 was epitaxially grown on the Si(100) substrate by chemical vapor deposition. Then, SrTiO3 or BaTiO3 was also epitaxially grown on the MgAl2O4 layer by means of rf magnetron sputtering. Epitaxial Y-Ba-Cu-O films were prepared on BaTiO3(SrTiO3)/MgAl2O4/Si substrates by rf magnetron sputtering. Preparation of an Y-Ba-Cu-O film directly on MgAl2O4/Si was also studied, but only a randomly oriented polycrystalline film has been obtained so far. Resistive superconducting transitions with zero resistance at 65 K on SrTiO3/MgAl2O4/Si and at 70 K on BaTiO3/MgAl2O4/Si were observed. [ABSTRACT FROM AUTHOR]

Thin films of the Bi2(Sr1-xCax)n+1CunOy (n=2, 3) system were prepared on (100)MgO substrates by coevaporation of Bi2O3, Sr-Ca alloy, and Cu metal. The lattice constant of the c axis of the low Tc (∼85 K) phase (n=2) decreased with increasing Ca composition x. The superconducting transition temperatures of both the low Tc phase and high Tc (∼110 K) phase (n=3) decreased with increasing x. These tendencies indicated that both the low Tc phase and the high Tc phase have a mutual solubility between Ca and Sr atoms in this Bi system and that the Tc ’s of these two phases are related to the c-axis lattice constant. [ABSTRACT FROM AUTHOR]

Superconducting Y1Ba2Cu3O7-δ films were prepared by TEA-CO2 pulsed laser evaporation. On SrTiO3(100) the a axis was oriented perpendicular to the substrate surface, while the <110> axis was oriented perpendicular to the substrate surface on SrTiO3(110). Sharp resistive superconducting transitions with zero resistance at 86 K on SrTiO3(110) and at 83 K on SrTiO3(100) were observed. [ABSTRACT FROM AUTHOR]

The as-grown crystallized films of low Tc phase (Tc∼80 K) in a Bi-Sr-Ca-Cu-O system were prepared by rf magnetron sputtering and were annealed in argon or oxygen atmosphere below 500 °C. Superconducting properties and the c-axis lattice constant varied according to the annealing temperature and atmosphere. These results suggest that the oxygen content in the film is varied by low-temperature annealing and that the variation of oxygen content affects the superconducting and structural properties. By cooling the sample in the chamber in 760 Torr oxygen, the as-grown film with Tc end at 74 K was obtained. [ABSTRACT FROM AUTHOR]

Transition temperature (Tc) control and annealing effects of Bi2.0Sr1.4Ca1.8Cu2.2Oy superconducting thin films implanted by 200 keV Ne+ have been investigated. Tc end points for 0.4-μm-thick Bi2.0Sr1.4Ca1.8Cu2.2Oy films for 0, 1×1012, and 1×1013 ions/cm2 doses are 78, 76, and 54 K, respectively. The ion dose, to achieve a nonsuperconductor for Bi2.0Sr1.4Ca1.8Cu2.2Oy films, is two or more orders of magnitude lower than that for YBa2Cu3O7-x films. The c-lattice constant increases were observed for the implanted films. Moreover, it was confirmed that the superconducting characteristics for the implanted films are recovered by annealing in O2 atmosphere. [ABSTRACT FROM AUTHOR]

Dependence of solid-phase growth of β-FeSi2 thin films on the crystal orientation of Si substrates has been investigated by using a-Fe (thickness: 20 nm)/c-Si(100), (110) and (111) stacked structures. X-ray diffraction (XRD) measurements suggested that the substrate orientation dependence of the formation rate of β-FeSi2 was as follows: (100)>(111)>(110). This dependence can be explained on the basis of the lattice mismatch between β-FeSi2 and Si substrates, i.e., the lattice mismatch between β-FeSi2(100) and Si(100), β-FeSi2(110) or (101) and Si(111), and β-FeSi2(010) or (001) and Si(110) of 1.4–2.0%, 5.3–5.5% and 9.2%, respectively. The substrate orientation dependence of solid-phase growth becomes relatively remarkable for very thin films. [Copyright &y& Elsevier]