ICMCTF2014 Session B1-1: PVD Coatings and Technologies

Liquid culture methods and plate counting methods are used to assess the antimicrobial performance of specimens. The antimicrobial rate against Escherichia coli (E. coli) under Japanese Industrial Standard JIS Z2801: 2000 is over 95%. The results show that the surface of SS 304 stainless steel substrate can be modified by deposited Zr-Cu-Ni-Al TFMG, and their improved anti-microbial efficiency against E. coli is attributed to their amorphous rough surface, and released copper ion.

Finally a Zr-Cu-Ni-Al TFMG with appropriate composition to exhibit improved hardness, thermal stability, and antimicrobial ability was revealed and discussed.

Growth of thin films by means of physical vapor deposition requires elevated substrate temperatures to ensure high adatom mobilities necessary for film densification. With no external heating applied during deposition resulting layers are underdense and exhibit poor mechanical properties. Bombardment of the growing film surface with gas ions accelerated in the intentionally applied electric field of the substrate helps to eliminate porosity through collisional increases in adatom mean free paths. [1] However, at higher incident ion energies, necessary to obtain densification, a steep price is extracted in the form of residual ion-induced compressive stress resulting from both recoil implantation of surface atoms and trapping of rare-gas ions in the lattice.

Here, we propose a new PVD method to grow dense, hard and stress-free thin films at low substrate temperature T_s, i.e., with no external heating applied. We use hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS and DCMS) [2,3] to grow Ti_1‑xTa_xN alloys. The Ta target driven by HIPIMS serves as the pulsed source of energetic Ta⁺/Ta²⁺ metal-ions, as determined by the in-situ ion mass spectrometry, while the Ti target operates in DCMS mode resulting in a continuous flux of metal atoms to sustain the high deposition rate. Substrate bias V_s is applied in pulses synchronized to the metal-ion phase of the HIPIMS discharge and the amplitude is varied from 20 to 280 V to investigate the effect of the bombarding Ta-ion energy on film properties. The densification of the magnetron sputtered film is achieved by pulsed bombardment with heavy Ta ions that are constituents of the alloy films and thus the excessive stresses are eliminated. The deposition rate is high (defined by the DCMS cathodes) and no external heating is used. We show that with as little as 8 mol% of TaN incorporated in the film, Ti_0.92Ta_0.08N alloys with high hardness can be obtained with T_s not exceeding 130 °C during the 1 h-long deposition; XTEM and STEM images reveal that upon Ta ion irradiation, the intracolumnar porosity observed in the reference TiN layer is greatly reduced. The films hardness and modulus of elasticity increase from 7.8 and 211 GPa for the reference TiN film deposited at T_s < 120 °C to 24.1 and 360 GPa for Ti_0.92Ta_0.08N layers prepared with V_s = 120 V.

Saunders and Miodownik [1] reported a model to predict metastable phase formation by estimating the migration distance of atoms. This model was critically appraised for the immiscible Cu–W system using both experimental and theoretical means. Cu–W thin films were synthesized by DC combinatorial magnetron sputtering. By applying X-ray diffraction, the phase formation was studied with respect to magnetron power density and substrate temperature. Then, a metastable Cu–W phase diagram was constructed. At 150 ^oC, it is observed that a two phase region containing bcc and fcc phases forms for Cu concentrations ranging from 73.6 and 82.4 at. %. This range broadens as the substrate temperature increases.

The random bcc and fcc Cu–W configurations were studied by ab initio calculations applying special quasirandom structures (SQS) and coherent potential approximation (CPA) approaches. The predicted lattice parameters and solubility limits are consistent with those determined by experiment.

[1] N. Saunders and A. Miodownik, J. Mater. Sci. 22 (1987) 629.

Despite its numerous advantages (flexibility, simple setup, coating quality), PLD is still very little utilized in real industrial coating and thin-film processes. The conventional PLD techniques, relying mainly on low repetition rate lasers and point sources, do not allow a large-scale or large-area coating with the high throughput, reliability, homogeneity, and reproducibility required in industrial processes.

Recently, thin-film coating technology has been developed which is based on ultra-short pulsed laser deposition (USPLD) enabled by the cutting edge, industrial laser technology utilized in machining. The industrial production capability and scalability of the technology is based on producing a line source of plasma instead of static point source of conventional PLD techniques. The technology is made possible by the high repetition rate and high average power of the new lasers combined with state-of-the-art, high-speed laser scanning technology. Together with the industrial approach which includes roll-to-roll production, the advantages of cold ablation (high-quality plasma, controlled ablation, reduced amount of particles) form a strong basis for scalable, high production rate ultra short pulsed laser deposition coating for variety of materials. Now, this technology has been made available with equipment. Here, we demonstrate the results produced using the equipment and the development of special coatings, especially B-C-N materials and composites based on, DLC, oxides, and metals, with the main focus in applications requiring wear resistance, tribological properties, optical quality, and/or biocompatibility.