Systematic studies of the effects of pulsed laser deposition processing parameters on plume dynamics and resultant film properties have been performed. Plume angular distributions, cosm(θ), were observed to be variable between 1 > m > 15 depending on laser energy density and spot size. Under optimized conditions, epitaxial, superconducting thin films could be grown in‐situ on a variety of single‐crystal substrates. High quality, 2000 Å  ss thick films were obtained at deposition rates approaching 150 Å/sec.

A comparison of the energetics and stoichiometry of effluents from YBa2CU307‐x targets ablated by Nd:YAG (1064 nm) and excimer (248 nm) lasers is presented. NdrYAG ablative processes are characterized by specularly directed neutral atom/cluster formation with translational energies in the range of 2 ‐ 20 eV. In sharp contrast, excimer ablation leads mainly to highly forward directed atomic ions with centroid energies between 200 and 400 eV. Analysis of the energetics indicates that different mechanisms are at play but both processes are non‐equilibrium in nature.

The formation of superconducting thin films on lanthanum aluminate substrates is very important for high‐frequency applications. In this paper, we discuss the fabrication of epitaxial superconducting YBa2Cu3O7 thin films on (100)LaAlO3 substrates, which exhibit excellent dielectric properties required for high frequency applications. The films were deposited by the biased pulsed laser evaporation technique (PLE) at substrate temperatures between 500‐650°C and exhibit excellent crystallinity with best minimum ion channeling yields corresponding to approximately 3%. The superconducting transition temperatures varied from 88‐92 K with critical current densities at 77K and zero magnetic field greater than 4 ‐ 5 x 106 Amps/cm2.

In this paper we present results of studies of the effect of process variations and substrate surface conditions on the microstructure and electrical properties of laser deposited YBa2Cu3O7‐δ thin films. The principle conclusions are as follows. The film properties of YBa2Cu3O7‐δ are relatively constant over a large range of substrate temperatures (620C‐720C) and oxygen pressures (150‐800 mT). There are small compositional variations with substrate temperature similar to, but much smaller than, those seen in reactively sputtered films. The best films were grown at 670C in 400mT of oxygen and have a zero resistance Tc of 89K and Jc > 1x106A/cm2 at 77K. There are, however, variations in the Tc, Jc, and orientation of films grown on MgO under similar deposition conditions. These variations reflect differences in the nucleation and growth process of YBa2Cu3O7‐δ on MgO which can arise from subtle changes in substrate surface properties. In particular, while the films are predominantly oriented with c axis perpendicular and a,b axes in the plane of the substrate along the MgO[100] direction, there are variable amounts of grains whose in‐plane orientations are at large angles to the MgO [100] direction, leading to large angle grain boundaries in some films. These large angle grain boundaries are correlated with the presence of Josephson weak links in some small constrictions for films on MgO.

Excellent quality epitaxial and textured superconducting HoBa2Cu307.x (Ho 123) thin films have been fabricated on lattice matched (100) KTaO3 and (100) LaAlO3, and lattice mismatched (100) MgO substrates by the pulsed laser evaporation (PLE) technique. A bulk Hol23 target was evaporated using nanosecond excimer laser pulses with the evaporating material depositing on a substrate maintained in the temperature range of 550‐650°C. The temperature for zero resistance for HoBa2Cu3O7_x films deposited on various substrates at 650°C varied between 85 to 89K. The epitaxial films deposited on (100) LaA103 substrates exhibited critical current densities greater than 3.5 x 106 Amps/cm2 at 77 K. The superconducting properties of the Ho 123 films were found to be similar to Y123 films.

K(Ta,Nb)O3 (KTN) is an interesting substrate for use in studies of epitaxial superconducting film‐substrate interactions because of a moderate lattice parameter mismatch with YBa2Cu3O7‐x and great versatility in electrical properties. KTN's properties are easily modified by doping to form an n‐type semiconductor and/or a ferroelectric with variable ferroelectric Tp. As an initial step in exploring such studies we have carried out what are believed to be the first epitaxial growth experiments of YBa2Cu3O7‐x films on insulating, semiconducting and ferroelectric KTN single crystals by pulsed laser ablation. We find that c‐axis‐normal epitaxial films can be consistently grown with TSc(R = 0) > 90K , △TSC ~1.5K, and Jc > IMA/cm2 on semiconducting and/or insulating KTaO3. However, growth on KNDO3 is problematic because of stresses generated by cooling the substrate through first order structural transitions, at even moderate cooling rates.

Epitaxial YBa2Cu3O7 (YBCO) films were grown on r‐plane A12O3 {1102} by laser ablation. X‐ray diffraction shows that films are epitaxial with the c‐axis perpendicular to the substrate and the a or b axes parallel to (2201), although the full width at half maximum of the rocking curve is larger compared to those of epitaxial films on SrTiO3. The critical temperatures (zero resistance) are between 85 K and 88 K with transition widths between 0.5 K and 3 K. The 300 K resistivity of 250 μΩextrapolates to zero at zero temperature and the critical current is as high as 5 x 106 A/cm2 at 4.2 K according to magnetization hysteresis measurements. Surface resistance data shows that 2000 Å thick epitaxial films on {1102} have about 1 mΩ at 13 GHz at 4.2 K.

Superconducting Y—Ba—Cu—O thin films with critical temperatures exceeding 80 K are deposited on silicon single crystal substrates using the pulsed laser deposition technique. Deposition from a sintered Y1 Ba2Cu3O7‐ target in oxygen ambient of 0.1 — 5 mbar onto substrates kept at 700°C to 820°C results in crystalline films in which the target composition of the metallic constituents is preserved. No post deposition treatments are required to obtain high values for the zero resistance. X— ray analysis as well as Raman spectroscopy reveal that specimens prepared at optimum conditions are single phase c—axis oriented. In contrast to films prepared on LaAlO3 or SrTiO3 the surface morphology shows a granular structure. The films prepared by this technique are quite stable against chemicals used in conventional lithographic patterning, however, a strong correlation between film quality before patterning and some degradation after patterning is observed.

We report in‐situ fabrication of c‐axis textured YBa2Cu3O7‐x superconducting thin films with Tco > 77K on unbuffered silicon substrates by the biased pulsed laser evaporation (PLE) technique in the temperature range of 550‐650°C. At substrate temperatures below 550°C, no c‐axis texturing of the superconducting film was observed. The YBa2Cu3O7‐x superconducting films were fabricated by ablating a bulk YBa2Cu3O7 target by a XeCl excimer laser (λ = 308 nm, τ = 45 × 10‐9 sec) in a chamber maintained at an oxygen pressure of 0.2 torr . The thickness of the films was varied from 0.3 to 0.5 nm depending on the number of laser pulses. Extensive diffusion was observed in thin films deposited at substrate temperatures above 550°C. However, microstructurally, with increase in the substrate temperature the films exhibited larger grain size and greater degree of c‐axis texturing (measured by the ratio of the (005) and (110) X‐ray diffraction peaks). This was found to give rise to better superconducting properties with Tco exceeding 77 K for YBa2Cu3O7‐x films deposited on Si substrates at 650°C.

YSZ [ (Y2O3)x (ZrO2)1‐x ] buffer‐layers for various compositions, x, and YBCO (Y1Ba2Cu3O7‐δ) films were grown on hydrogen‐terminated Si(100) substrates by laser ablation. The structural and electrical properties of the YBCO are found to depend strongly on x, and to be optimized near x=0.1.

The electric resistance was measured in real time during laser evaporation deposition of superconducting thin films. It was found that different substrates led to different behaviors in the temporal change of the resistance. The results are consistent with the processes of nucleation, interface reaction and bulk‐like growth. Structural transformation was also observed due to oxygen backfilling at the final stage of the deposition.

The fluorescence emission spectra from the plasma plume induced by ArF excimer laser irradiation of YBa2Cu3O7‐x was studied and compared to the spectra of Y, YO, Cu, CuO, and YCuO under similar conditions. The only compound detected in the Y‐Ba‐Cu‐O ablated material spectra was YO. Spatially resolved measurements from the plasma plume emanating from the irradiated superconducting material were performed also as a function of distance from the surface.

The effect of laser ablation on the morphology and composition of the irradiated YBa2Cu3O7‐x material was studied by SEM and EDAX. It was found that the 1‐2‐3 composition ratio of the near surface region was maintained after ablation. Changes in the morphology were observed in the track region and three distinctive regions could be identified as a function of distance from the beam center.

Optical absorption in the plume produced by excimer laser ablation of Y1Ba2Cu3O7‐x under film growth conditions has been observed for the first time and used to characterize the transport of ground state Y, Ba, and Cu neutrals as well as Y+ and Ba+ ions. Spatially and temporally resolved absorption measurements (0.6 mm, 20 ns resolution) indicate significant ground state number densities at times following the laser pulse that are up to an order of magnitude longer than the duration of fluorescence from excited states. Time‐of‐flight absorbance profiles result in velocity distributions that are broadened significantly toward lower velocities and reveal a low velocity component (<10 5 cm s_1) to the ablation process which is not observed using emission spectroscopy. Electric ion probe measurements of the time dependence of Y+ ions confirm the existence of the new, slow velocity component. Electron densities >1016 cm‐3 in the white plasma close to the pellet have been estimated using spectrally broadened emission lines. The effects of oxygen ambient pressures and the detection of YO, BaO, and CuO also are reported. This technique is applicable as an situ monitor of the kinetic energy of ablated species during low temperature deposition of epitaxial 1:2:3 superconducting thin films.

Angular variation of x‐ray fluorescence due to oxygen atoms in high‐T Y‐Ba‐Cu‐O thin films is measured for the first time by using a new parallel plate avalanche chamber. This technique allows the possibility of nondestructive probing of the depth‐profile of oxygen atoms in the superconducting materials. Our preliminary results indicate that the near surface region of the Y‐Ba‐Cu‐O film may contain an oxygen‐depleted layer of thickness around 20 nm.

The fabrication of high quality thin films often depends on the early stages of the growth process during which epitaxy is established. The substrate surface structure generally plays a critical role at this stage. Many observations of the high‐Tc superconductor film‐substrate interface structure and chemistry have been made by transmission electron microscopy (TEM) of cross‐section samples. Ion‐milling induced damage, however, can be severe in these specimens. In the present study, the early stages of the growth of high Tc superconducting thin films of YBa2Cu3O7δ have been studied by TEM using a technique which requires no post‐deposition specimen preparation.

Grain boundaries in YBa2Cu3O7-δ thin films deposited on (001)-MgO by pulsed laser ablation have been characterized using selected area diffraction. In addition to twin boundaries, the presence of both low-angle and high-angle grain boundaries were characteristic of the film's microstructure. The presence of certain grain boundaries may be responsible for the weak-link Josephson behavior observed in small constrictions formed in superconducting films on MgO.

We investigate, in this study, the laser evaporation processes for the deposition of YBaCuO and BiSrCaCuO compounds, using a pulsed ArF (193 nm) excimer laser. The deposition parameters, especially those which are relevant to the geometrical configuration and optical arrangement of the experimental set-up and laser irradiation conditions are examined in details.

High To superconducting Bi-(Pb-)Sr-Ca-Cu-O thin films were ablated on MgO(l00) substrates at room temperature using a Nd:YAG laser at 1064 or 532 nm. The target materials had compositions near Bi2-xpbxSr2Ca2+yCu3+zOy (x<0.6, y,z<l) and their zero resistivity temperatures were 101 - 105 K. The amorphous films were crystallized either by annealing near 850°C or they were first melted and then annealed. The effects of laser ablation parameters and annealing conditions were investigated. The films were studied by XRD, SEM/EDS and resistivity measurements.

The best films were annealed near 850 °C and they consisted mainly of the 2223 phase. These films had T9(midpoint) at 107 K and zero resistivity at 100 K. In the melt-treated films the amount of the 2223 phase as well as Tc was lower. The superconducting phases in the annealed films were strongly oriented with their c-axes perpendicular to the substrate surface.