Power Impulse Magnetron Sputtering Deposition Research Articles

The comparative study of electrical, optical and catalytic properties of Co3O4 thin nanocrystalline films prepared by reactive high-power impulse and radio frequency magnetron sputtering

This paper deals with the investigation of optical and electrical properties of Co3O4. Their impact on catalytic activity in ethanol dehydrogenation is observed. The change in conductivity is provided by intentionally heating the samples in-situ, variation of oxygen flow rate, introduction of the forming gas (10% H2 in N2) and the application of different deposition regimes. Pure Co3O4, as well as deposited catalysts under a forming gas atmosphere are studied. The deposition of the samples on glass and stainless steel substrates is carried out by means of magnetron sputtering. Both radio-frequency and high power impulse magnetron sputtering deposition technologies are applied. By means of these deposition regimes we managed to obtain films with different conductivity and crystalline structure. The morphology of the films is studied by scanning electron microscopy. The crystalline structure and the surface chemical composition of Co3O4 are investigated using X-ray diffraction and X-ray photoelectron spectroscopy. Electrical and optical properties of catalysts are studied by resistance and optical spectroscopy measurements. The catalytic activity of the films is tested on the reaction of ethanol dehydrogenation by means of selected ion flow-drift tube mass spectrometry.

Electric and magnetic fields synergistically enhancing high power impulse magnetron sputtering deposition of vanadium coatings

The high power impulse magnetron plasmas (HIPIMS) were employed as a novel deposition technique, which had the benefit of providing a high ionization degree. In contrast, due to the ion return effect, the deposition rate was relatively low compared to the conventional direct current. In this paper, the external electric field and external magnetic field enhanced simultaneously the HIPIMS ((E-MF)-HIPIMS) to achieve higher deposition rate of the coatings. The vanadium coatings were deposited by the (E-MF)-HIPIMS at equivalent average target powers. The substrate peak ion current density measured in the (E-MF)-HIPIMS mode was increased by a factor of 4 to the discovered current density for the HIPIMS conditions when the anode voltage was set to 70 V. The enhanced ion flux bombardment from the highly ionized (E-MF)-HIPIMS plasma led to the formation of a smoother surface and a denser structure. At the same average target power for the vanadium coatings depositions, the (E-MF)-HIPIMS exhibited higher deposition rates compared to the conventional HIPIMS by approximately 73%. The (E-MF)-HIPIMS sputtered vanadium coating exhibited significantly higher-sized film and substrate interface bonding strengths than compared to the HIPIMS by the Rockwell adhesion testing. In addition, the (E-MF)-HIPIMS sputtered vanadium coating exhibited an improved friction coefficient and improved corrosion resistance compared to the substrate and the HIPIMS sample. The improvement occurred due to the enhanced particle ionization and intense ion bombardment.

Rolling contact fatigue of bearing components coated with carbon nitride thin films

Bearing rollers were coated with CNx films using high power impulse magnetron sputtering deposition in order to reduce their rolling-contact fatigue as investigated using a Micro-Pitting Rig tribometer under poly-alpha-olefin lubricated conditions. Coated rollers with a ~15nm thick W adhesion layer to the substrate, exhibit the best performance, presenting mild wear and no fatigue after 700 kcycles. The steady-state friction coefficient was ~0.05 for both uncoated and coated rollers. Uncoated rollers show run-in friction in the first 50 kcycles, because of steel-to-steel contact, which is absent for coated rollers. Analytical transmission electron microscopy and X-ray photoelectron spectroscopy show that the presence of a CNx coating prevents steel-to-steel contact of the counterparts, prior to the elastohydrodynamic lubrication, reducing their wear and increasing the lifetime expectancy.

Method to control deposition rate instabilities—High power impulse magnetron sputtering deposition of TiO2

The authors describe how changes in shutter state (open/closed) affect sputter plasma conditions and stability of the deposition rate of Ti and TiO2 films. The films were grown by high power impulse magnetron sputtering in pure Ar and in Ar/O2 mixture from a metallic Ti target. The shutter state was found to have an effect on the pulse waveform for both pure Ar and reactive sputtering of Ti also affecting stability of TiO2 deposition rate. When the shutter opened, the shape of pulse current changed from rectangular to peak-plateau and pulse energy decreased. The authors attribute it to the change in plasma impedance and gas rarefaction originating in geometry change in front of the magnetron. TiO2 deposition rate was initially found to be high, 1.45 Å/s, and then dropped by ∼40% during the first 5 min, while for Ti the change was less obvious. Instability of deposition rate poses significant challenge for growing multilayer heterostructures. In this work, the authors suggest a way to overcome this by monitoring the integrated average energy involved in the deposition process. It is possible to calibrate and control the film thickness by monitoring the integrated pulse energy and end growth when desired integrated pulse energy level has been reached.

Friction at single-asperity contacts between hydrogen-free diamond-like carbon thin film surfaces

This work investigates the friction and adhesive forces at the single-asperity contact between hydrogen-free diamond-like carbon (DLC) coated surfaces in humid air and in argon. High power impulse magnetron sputtering deposition has been used to produce hydrogen-free DLC thin films on commercial silicon AFM tips and silicon wafers. The structure and surface morphology of the deposited DLC films has been investigated by X-ray photoelectron spectroscopy and tapping AFM, investigations that showed very smooth DLC films with about 29% of sp3 C−C bonds. The as-deposited hydrogen-free DLC thin films were hydrophilic (water contact angle about 65°) due to incorporation of a small amount of oxygen (about 9% of C=O bonds) at the film surfaces. The friction force measurements show that at low normal loading force the contact friction is much lower in the humid air than in the argon, while at large values of the loading force the contact friction does not depend on the measurement medium. A qualitative friction model based on the concept of dry and wet friction regimes, when the layer of water adsorbed on DLC film surfaces plays the role of lubricator, is proposed to explain these findings.

Angle-resolved investigation of ion dynamics in high power impulse magnetron sputtering deposition system

The high power impulse magnetron sputtering deposition system (HiPIMS) equipped with 5cm in diameter titanium target has been investigated by means of time-resolved modified Katsumata probe. The probe allows for determination of the ion velocity distribution function. However, the modified Katsumata probe is unable to resolve the mass of ions. On the other hand, compact construction of modified Katsumata probe allows us to place the probe in an arbitrary position with respect to planar magnetron. The present construction of modified Katsumata probe allows reaching the acceptance angle of about 15°. The ion velocity distribution function (IVDF) in forward direction is then directly proportional to the derivative of measured ion current with respect to the retarding potential. An angle-resolved study of HiPIMS system operating in the reactive atmosphere has been carried out. The effect of oxygen partial pressure on measured IVDF at different angles within the plasma pulse has been investigated. The total pressure was held at 1Pa together with the constant pulse-on time of 100μs, pulse frequency of 100Hz and mean discharge current of 500mA for all the experiments. The results revealed inhomogeneous ion fluxes in different directions from the target especially for reactive atmosphere. The IVDFs measured at angle 45° demonstrated significantly enhanced energy tail in contrast to dc magnetron or mid-frequency pulsed-dc magnetron. Furthermore, higher oxygen partial pressure indicated broader IVDF for all the angles together with a slight shift of IVDF peak to negative values indicating the negative plasma potential.

Endurance of aircraft gas turbine mainshaft ball bearings—Analysis using improved fatigue life theory. I. Application to a long-life bearing : Ioannides, E., Harris, T.A. and Ragen, M.J. Tribology (Trans. ASME) Apr. 1990 112, (2), 304–308

Bearing rollers were coated with CNx films using high power impulse magnetron sputtering deposition in order to reduce their rolling-contact fatigue as investigated using a Micro-Pitting Rig tribometer under poly-alpha-olefin lubricated conditions. Coated rollers with a ~15 nm thick W adhesion layer to the substrate, exhibit the best performance, presenting mild wear and no fatigue after 700 kcycles. The steady-state friction coefficient was ~0.05 for both uncoated and coated rollers. Uncoated rollers show run-in friction in the first 50 kcycles, because of steel-to-steel contact, which is absent for coated rollers. Analytical transmission electron microscopy and X-ray photoelectron spectroscopy show that the presence of a CNx coating prevents steel-to-steel contact of the counterparts, prior to the elastohydrodynamic lubrication, reducing their wear and increasing the lifetime expectancy.