X. Queralt

Preparation of SrTiO3 thin films on Si(100) substrates by laser ablation: Application as buffer layer for YBa2Cu3O7 films

SrTiO3 thin films have been deposited on Si(100) by pulsed laser ablation. The films were characterized by x‐ray diffractometry, field emission scanning electron microscopy, and secondary ion mass spectrometry. The films show the (h00) or (hh0) preferential orientations depending on the substrate temperature and oxygen partial pressure during the deposition. Depth profiles indicate that films grow without an important reaction with the substrate. Superconducting YBa2Cu3O7−x thin films were successfully deposited by laser ablation on Si(100) substrates coated with SrTiO3 buffer layer. This indicates that SrTiO3 is a good material as a buffer layer for deposition of YBa2Cu3O7−x on silicon.

Superconducting YBa2Cu3O7 films deposited on Si (100) substrates with CeO2 buffer layers by laser ablation

Abstract Superconducting YBa 2 Cu 3 O 7 (YBCO) thin films have been deposited on Si (100) substrates with CeO 2 buffer layers by laser ablation. The films were characterized by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS) and four-point electrical resistivity. Secondary ion mass spectrometry results indicate low interdiffusion between Si, CeO 2 and YBCO. The best YBCO films are textured with c -axis perpendicular to the substrate and their resistance exhibits a normal state metallic behavior with zero resistance around 84 K. The crystalline and electrical properties of YBCO films were related with the substrate temperature. A minimum substrate temperature is necessary to deposit good superconducting YBCO films. Moreover, there is a maximu temperature to obtain c -orientation, although the electrical properties are not degraded yet.

Erbium oxide thin films on Si(100) obtained by laser ablation and electron beam evaporation

Abstract Erbium oxide thin films have been obtained by laser ablation and electron beam evaporation techniques on Si(100) substrates. The samples were grown under different conditions of oxygen atmosphere and substrate temperature without any oxidation process after deposition. The crystal structure has been studied by X-ray diffraction. Films obtained by laser ablation are highly textured in the [ hhh ] direction, although this depends on the conditions of oxygen pressure and substrate temperature. In order to study the depth composition profile of the thin films and the interdiffusion of erbium metal and oxygen towards the silicon substrates, X-ray photoelectron spectroscopy analyses have been carried out.

Deposition of YBa2Cu3Ox by laser ablation on Si(100) using different buffer layers

Abstract Superconducting YBa 2 Cu 3 O x (YBCO) thin films have been obtained on Si(100) substrates with yttria-stabilized zirconia (YSZ), CeO 2 and SrTiO 3 buffer layers. The YBCO and the buffer films were deposited by laser ablation. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and four-contact electrical resistivity. X-ray diffraction spectra show well oriented buffer layers and secondary ion mass spectrometry results indicate low interdiffusion between YBCO, buffer layers and Si. YBCO films with the c -axis perpendicular to the substrate are obtained for the three materials used as buffers. The best films show a normal state metallic behaviour with zero resistance around 84 K. The crystalline and electrical properties of the films are related with the substrate temperature. The substrate temperature range for the best properties depends on the nature of the buffer layer.

YBa2Cu3O,7 − x superconducting thin films by sequential evaporation on alumina substrates

Abstract Superconducting Y-Ba-Cu-O thin films have been formed on alumina substrates by sequential evaporation of ten Cu Y 2 O 3 BaF 2 layered structures and subsequent heat treatments. The best film showed a superconducting onset temperature of 92 K and a zero resistance at 50 K. The film properties were studied using electrical measurements, scanning electron microscopy, x-ray diffraction and secondary ion mass spectrometry.

Deposition of Er2O3 thin films on Si(100) by laser ablation

Abstract Er 2 O 3 thin films have been grown on Si(100) substrates by laser ablation. Films have been deposited in an ultra-high vacuum system under different conditions of oxygen pressure and substrate temperature. The crystalline structure, determined by X-ray diffractometry, depends on the deposition parameters. The best films have the simple cubic phase ( a = 10.548 A ) of Er 2 O 3 with hhh preferential orientation, without peaks corresponding to other phases or orientations. Depth composition has been studied by means of secondary ion mass spectrometry, in order to determine the depth homogeneity of the film and the interaction with the substrate.

CeO 2 /YSZ and SrTiO 3 /YSZ Double Buffer Layers Deposited on Si(100) by Laser Ablation

Yttria stabilized zirconia (YSZ), SrTiO 3 and CeO 2 thin films have been widely used as buffer layers in YBa 2 Cu 3 O 7-x (YBCO) deposition on silicon substrates. YBCO superconducting properties are limited by lattice mismatches between YSZ and YBCO, and chemical interaction of CeO 2 and SrTiO 3 with silicon. In order to avoid these problems we have deposited CeO 2 /YSZ/Si(100) and SrTiO 3 /YSZ/Si(100) bilayers by laser ablation. Wide temperature and pressure ranges have been studied. The influence of the intermediate layer on the CeO 2 and SrTiO 3 films properties has been studied. Previous studies were performed on films of each material on Si(100) and YSZ(100) single crystals. The surface of the films and bilayers is smooth without microcracks and only few droplets are found. Only small interdiffusion is observed in all the cases. Texture of the films changes with deposition conditions. Epitaxial growth of CeO 2 has been found both on YSZ(100) single crystals and YSZ buffers on Si(100).

Laser Ablation Deposited YBa 2 Cu 3 O x , Thin Films on YSZ/Si(100)

Superconducting YBa 2 Cu 3 O x (YBCO) thin films have been deposited on Si(100) substrates with yttria-stabilized zirconia (YSZ) buffer layers by laser ablation. Buffers have been obtained by laser ablation as well. The films have been characterized by scanning electron microscopy, x-ray diffractometry, secondary ion mass spectrometry, and four-contact electrical resistivity measurements. Secondary ion mass spectrometry results indicate very low interdiffusion between Si, YSZ and YBCO. The best YBCO films are textured with c axis perpendicular to the substrate and their resistance shows a normal state metallic behavior with zero resistance at temperatures higher than 80 K. The properties of YBCO films have been related with the substrate temperature and oxygen partial pressure during deposition.

Superconducting Y-Ba-Cu-O thin films on silicon and Al2O3 substrates

Abstract YBaCuO superconducting thin films have been prepared by sequential evaporation of copper, Y 2 O 3 and BaF 2 layers on Si[100] and polycrystalline Al 2 O 3 substrates. Such sequences were evaporated 1, 10 or 30 times on Si[100] with a 0.5 μm ZrO 2 buffer layer. The effects of different buffer layers were studied for Al 2 O 3 substrates by means of the deposition of ZrO 2 , copper, silver and BaTiO 3 layers with thicknesses of 20, 100 and 500 nm. The film properties were studied using electrical measurements, scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectrometry and secondary ion mass spectrometry. The best properties were obtained for the obtained on ZrO 2 /Si[100] with a single evaporation sequence. The studies of the different buffers reveal a strong dependence of the film properties on the nature and thickness of the buffer, with the best results for films deposited on a silver layer.

Superconducting Y-Ba-Cu-O thin films on Si and Al 2 O 3 substrates

YBaCuO superconducting thin films have been prepared by sequential evaporation of Cu, Y 2 O 3 and BaF 2 layers on Si[100] and polycrystalline Al 2 O 3 substrates. One, ten and thirty-sequences were evaporated on Si[100] with a 0.6 μm ZrO 2 buffer layer. The effects of different buffer layers were studied for Al 2 O 3 substrates by means of the deposition of ZrO 2 , Cu, Ag and BaTiO 3 layers with thicknesses of 20, 100 and 500 nm. The film properties were studied using electrical measurements, scanning electron microscopy, x-ray diffractometry, electron microprobe analysis and secondary ion mass spectrometry. The best properties were found in the film obtained on ZrO 2 /Si[100] with one-sequence. The studies of the different buffers show a strongly dependence of the film properties on the nature and thickness of the buffer, with the best results for films deposited on an Ag layer.