The microstructures of Tl2Ba2Ca1Cu2O8 (Tl-2212) films are very strongly influenced by the processing parameters used to synthesize the superconducting phase and also control the microwave surface resistance values that are of key importance in the application of these materials in high-frequency devices. We report here on detailed studies of how the mesotexture of Tl-2212 films develops during synthesis at 820 and 855 °C. Our key observation is that the microstructure, and hence the superconducting properties, are controlled by the mechanism by which stress is relieved in the films and that apparently perfectly epitaxial films do not have the best microwave performance because in these samples the stress is relieved by macroscopic defects rather than local, low-angle grain misorientations.

An as-deposited Al–Cu–Fe–Cr film was annealed in flowing argon to study development of a quasicrystalline approximant microstructure. Sputter profile x-ray photoemission spectroscopy analysis showed oxygen incorporation reached approximately 70 at.% at the surface of the film, declined monotonically, and stabilized at ∼10 at.% at a depth of 160 nm. Synchrotron grazing incidence x-ray scattering was used to probe the structure of the coating at various penetration depths by altering the angle of the incident x-ray beam. An amorphous structure was observed near the termination surface, which coexisted with a compressively strained crystalline aluminum. These phases were the dominant microstructure to a depth of 110 nm. Below 150 nm, the film was primarily O1 decagonal approximant. Cross-section transmission electron microscopy elucidated a columnar growth morphology with associated porosity in the interstices between the columns. The resulting development of the Al–Cu–Fe–Cr decagonal approximant coatings from the precursor is reported.

Quasicrystalline films were formed by RF sputtering from a powder composite target onto Inconel substrates, which produces a polymorphic nanoquasicrystalline grain structure, ~2.5 - 10 nm. Subsequent annealing at 500°C for 4 hours, at base pressures of below 5*10-5 Torr, and with Ar flow to 5 - 10 mT, fully develops the quasicrystalline structure with decagonal phase predominating, except near the termination surface. Analysis by XPS indicated extensive oxygen incorporation and limited aluminum enrichment at the termination surface. These results are correlated with structure and strain analysis via synchrotron grazing incidence x-ray scattering (GIXS). By varying the incident angle, hence the x-ray penetration depth, the evolution of an amorphous and crystalline crystalline secondary phases at the surface of the film has been detected. Residual strain analysis shows that this second phase induces a compressive residual strain of 0.10% as measured from the displacement of the major quasicrystalline peaks in the surface layers of the film.

Nanoindentation experiments have been performed to assess the mechanical behavior of chromium nitride (CrxNy) thin films sputtered in different deposition geometries and with varying Ar and N2 pressures. The hardness and elastic modulus of chromium nitrides are of great interest with regard to their applications. In the present work, two different deposition geometries, i.e. multi-substrate and confocal, were used to sputter (DC magnetron) a CrxNy layer on Si (100) wafers at varying nitrogen flow rates. The results of the nanoindentation experiments indicate that, over a similar argon and nitrogen regime, the CrxNy films grown in a multi- substrate geometry exhibit higher hardness and elastic modulus on the average than those grown in the confocal geometry. Furthermore, it was found that in the multi-substrate geometry the hardness and elastic modulus of the films were significantly higher than those in the confocally deposited films for a specific regime of the nitrogen flow rate (10-14 sccm). Finally, observations of the mechanical properties trends could be correlated with a higher degree of anisotropic stress for films grown in the multi-substrate in comparison to the confocal geometry.

Thallium based high temperature superconducting films were formed on LaAlO3 (LAO) substrates by thalliation of sputtered amorphous precursor films by reaction with Tl2O. High resolution strain measurements and diffraction topographic imaging studies were performed using the synchrotron at Stanford Synchrotron Radiation Laboratory (SSRL). From these results, we have reached preliminary conclusions regarding the effect of film strain and substrate twinning on the superconducting properties of Tl-2212 films on LAO substrates. High- resolution strain measurements showed a correlation between film strain and microwave properties. The relative strain in samples in which Q>105 at 5.55 GHz (at 50 K) was approximately 30% lower than that in samples in which Q<104 when tested under the same conditions. Examination of samples where Q<104 at 5.55 GHz (at 50 K) by SEM also indicated microstructure defects that are typical in films with a high level of residual stress. White beam x-ray diffraction topographic analysis was used to quantitatively measure the degree of twinning in the substrate. The results will discuss the relationship between the measured Q values of the microwave cavity and the strain state, microstructure and defect morphology in the superconducting film/substrate couple.

Analysis of the phase relationships of Al-Cu-Fe-Cr based sputtered films, before and after various annealing treatments, was carried out via grazing incidence x-ray scattering (GIXS) at SSRL on beamline 7-2. The “as-deposited” films were composed primarily of nanoscale grains whose structure were mainly quasicrystalline (QC) and its approximants, plus a nano-crystalline phase was also observed in one sample. None of these precursor films exhibited any degree of amorphous character. GIXS studies, in the symmetric and asymmetric modes, revealed that grain growth due to the post-deposition heat treatments caused a decagonal QC phase to evolve and dominate the crystalline phases, which composed the film. These ≍10 µm thick films were created by sputter deposition with a DC magnetron source via an Al-Cu-Fe-Cr powder pressed target, giving a nominal sample composition of Al75Cu4Fe8Cr10O3. Two types of annealing treatments were performed using an Argon atmosphere. Anneal of a precursor film for 4 hours at 500°C showed a large fraction of decagonal and approximant phases, while anneal of a precursor film for 2 hours at 400°C and 2 hours at 550°C showed a large fraction of the crystalline phase.

The evolution of texture in thin films must be fully understood in order to take advantage of favorable crystallographic orientations in a material for a given application. The development of an out-of-plane texture (preferred crystallographic orientation in the growth direction) and an in-plane texture (preferred crystallographic orientation in the plane of growth) in sputter deposited, thin mo films on Si was studied using transmission electron microscopy and diffraction, and conventional x-ray pole figures. For a range of deposition parameters, a strong (110) out-of-plane texture developed within 1000Å, while a strong in-plane texture did not develop until a thickness of about 1 μm.

It is important that inherent strains (or stresses) be controlled during thin film processing. This study used grazing incidence x-ray scattering (G1XS) to determine the strain gradient present in a ∼1700 Å sputtered molybdenum thin film. In particular, the gradient in the hydrostatic strain was Measured. This observation corresponded to assessing the average change in the lattice parameter as a function of depth throughout the thickness of the film. In addition, the strain ellipsoids, which represent the state of strain in three dimensions, were calculated as a function of film depth. It was shown that the strain varied throughout the ∼1700 Å Mo film thickness and that the principal strains were anisotropic, with one principal strain much larger than the others in Magnitude.