Nanostructured Ti–Ta thin films synthesized by combinatorial glancing angle sputter deposition

Abstract

Ti-Ta alloys are attractive materials for applications in actuators as well as biomedical implants. When fabricated as thin films, these alloys can potentially be employed as microactuators, components for micro-implantable devices and coatings on surgical implants. In this study, Ti Ta (x = 21, 30) nanocolumnar thin films are fabricated by glancing angle deposition (GLAD) at room temperature using TiTa and Ta sputter targets. Crystal structure, morphology and microstructure of the nanostructured thin films are systematically investigated by XRD, SEM and TEM, respectively. Nanocolumns of ∼150-160 nm in width are oriented perpendicular to the substrate for both TiTa and TiTa compositions. The disordered α″ martensite phase with orthorhombic structure is formed in room temperature as-deposited thin films. The columns are found to be elongated small single crystals which are aligned perpendicular to the [Formula: see text] and [Formula: see text] planes of α″ martensite, indicating that the films' growth orientation is mainly dominated by these crystallographic planes. Laser pre-patterned substrates are utilized to obtain periodic nanocolumnar arrays. The differences in seed pattern, and inter-seed distances lead to growth of multi-level porous nanostructures. Using a unique sputter deposition geometry consisting of TiTa and Ta sputter sources, a nanocolumnar Ti-Ta materials library was fabricated on a static substrate by a co-deposition process (combinatorial-GLAD approach). In this library, a composition spread developed between TiTa and TiTa, as confirmed by high-throughput EDX analysis. The morphology over the materials library varies from well-isolated nanocolumns to fan-like nanocolumnar structures. The influence of two sputter sources is investigated by studying the resulting column angle on the materials library. The presented nanostructuring methods including the use of the GLAD technique along with pre-patterning and a combinatorial materials library fabrication strategy offer a promising technological approach for investigating Ti-Ta thin films for a range of applications. The proposed approaches can be similarly implemented for other materials systems which can benefit from the formation of a nanocolumnar morphology.

Compositional and Tribo‐Mechanical Characterization of Ti‐Ta Coatings Prepared by Confocal Dual Magnetron Co‐Sputtering

“…The cross sections and surface morphology of the coatings deposited on Si substrates are presented in Figure and, respectively. A typical close‐packed columnar growth (Figure ) can be observed for all the films independently of the Ta content . It is interesting to note that the images show a dimple‐like structure indicative of the ductile fracture mechanism of the metallic coatings, very different to that observed for ceramic coatings.…”

“…Motemani et al did also observed the formation of the metastable α̋ martensite phase in the as‐deposited coatings for Ta contents between 30 and 33 at%. The phase diagrams of metastable phases for the Ti‐Ta system indicates that the martensitic transformation ( M s ) temperature decreases as a function of the concentration of the β stabilizer .…”

“…This memory effect was investigated by Motemani et al in Ti‐Ta coatings produced by magnetron sputtering. Montemani et al results indicated that by using magnetron co‐sputtering, it was possible to obtain the α″ martensitic phase in the as‐deposited room temperature films for Ta contents between 30 and 33 at%. They observed the martensitic transformation between 225–250 °C, making the material useful to produce high temperature actuators for micro‐electromechanical systems.…”

“…The martensitic phases also lead to other exotic properties, such as shape memory effects . This memory effect was investigated by Motemani et al in Ti‐Ta coatings produced by magnetron sputtering. Montemani et al results indicated that by using magnetron co‐sputtering, it was possible to obtain the α″ martensitic phase in the as‐deposited room temperature films for Ta contents between 30 and 33 at%.…”

Biomimetic Coatings Obtained by Combinatorial Laser Technologies

“…The literature proposes various approaches to fabricate combinatorial coatings, most of them being suitable only to a limited class of compounds. Among these, we can mention several physicalchemical deposition methods such as magnetron co-sputtering deposition [141], glancing angle deposition [142], co-electrodeposition [143], casting processes [144], or flow-coating methods [145]. An advanced experimental design could be envisioned in order to generate multi-compositional diagram 2D maps on high surface areas.…”