Filtered Arc Deposition Technique Research Articles

Plasma distribution properties of vacuum ribbon-like cathodic arc plasma fliter and Raman studies of diamond-like carbon films perpared by it

As is well known, most filtered cathodic vacuum arc deposition technology adopts filters with various geometries to remove macro particles in the last three decades, but almost all of them have a circular cross-section. Compared with the traditional toroidal duct filters, the rectangular graphite cathodic arc source can have a larger area which can be an arc source of a ribbon-like cathodic arc plasma filter, which has a higher coating efficiency due to its larger area arc source and may be more suitable for a larger scale industrial production. Thus, the research on the plasma distribution properties within the vacuum ribbon-like cathodic arc plasma filter is of great significance. In this paper, a rectangular graphite cathodic arc source is used to produce the ribbon-like cathodic arc plasma. Within the filter, a 90 curved magnetic duct with a rectangular cross-section is used as the arc filter. The ribbon-like cathodic arc plasma is transmitted from cathode to the deposition area along the magnetic line produced by external coils. A Faraday cup ion energy analyzer and a Langmuir probe are used to characterize the distribution properties of the filtered plasma at 15 places on the exit plane. Ion energies and ion density at these positions are obtained. For the special retrograde motion of the cathode spot on the rectangular target surface, the ion energies and ion density data are not stable. In order to obtain representative values, the net results are the average value of 3 measurements. Diamond-like carbon (DLC) films are deposited by the ribbon-like cathodic arc plasma filter at the same exit plane and their structures are characterized by Raman shift. To compare the distinctness of the 15 Raman spectrums, each Raman spectrum of the DLC films is normalized and shown in a figure. Meanwhile, the thicknesses of all the DLC films are measured by step profiler. Results show that the ion energies are of Maxwell distributions at all the 15 places on the exit plane. The ion energies vary from 0 to 60 eV, most being in the range from 20 to 30 eV. The arc voltage is 30 eV, which exactly coincides with the ion energies. While Raman spectra of the DLC films show an obvious correspondence relationship with the ion energies as well as the ion density and the DLC film thickness. The nano-hardness of the DLC films lies in a range of 25-43 GPa. Although the ion energies, ion density, DLC film thickness and nano-hardness are slightly different at different locations, they are not significant. Owing to the relatively evenly distributed properties of the ribbon-like arc plasma this may open great opportunities for a large area filtered arc deposition technique.

TiCN coatings deposited by large area filtered arc deposition technique

Nanocrystalline TiCN coatings were deposited from Ti targets under the atmosphere of mixed N2 and CH4 gases using a novel large area filtered arc deposition technique at a temperature of 350 °C. The microstructure, crystalline structure, bonding structure, coating composition, hardness, modulus, plasticity, and adhesion of the deposited TiCN coatings were systematically characterized using optical microscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy, nanoindentation, Rockwell adhesion test, and scratch adhesion test, respectively. By adding 5% CH4 gas into the chamber, only 2.31 at. % of C was incorporated into the TiN coating to form Ti–C bonds. However, XRD results show a drastic change in the preferred orientation of the TiN grains from strong (111) to strong (220) orientation, as well as a decrease in grain size. Nanoindentation tests indicate a significant increase in hardness and elastic modulus. The plasticity and toughness of the TiCN coatings are comparable to that of the TiN coatings. Adhesion tests show that the TiCN coatings possess excellent adhesion on both 316 and 440a stainless steel substrates.

Influence of Si content on the structure and internal stress of the nanocomposite TiSiN coatings deposited by large area filtered arc deposition

TiSiN coatings were deposited by using a large area filtered arc deposition technique from TiSi targets with different Si content. The influence of the Si content in the targets on the surface morphology, composition, bonding structure, crystalline structure and internal stress of the TiSiN coatings were systematically studied by using scanning electron microscopy, x-ray photoelectron spectroscopy, x-ray diffraction and the substrate curvature method, respectively. It was found that by increasing Si content in the TiSi targets to 20 at%, the Si content in the coatings increases linearly to 7.7 at%. Both XRD and XPS results indicate that all the TiSiN coatings consist of a nanosized TiN phase and an amorphous Si3N4 phase except for the coatings with Si content of above 4.5 at%, in which 5% of amorphous TiSi2 phase exists. With increasing Si content in the coating, the coatings change orientation from the (1 1 1) to the (2 2 0) preferred orientation. The TiN grain size decreases linearly to 5.4 nm with an increase in Si content up to 4.5 at%, and then increases slightly with a higher Si content in the coatings. The substrate curvature method shows that the increase in the Si content from 0 to 4.5 at% results in a rapid increase in the internal stress in the coating from 2.2 to 3.9 GPa, but a further increase in the Si content leads to a slight decrease in the internal stress in the coating. The decrease in the grain size with increasing Si content contributes to the increase in the internal stress in the TiSiN coatings.

Nanocomposite TiSiN coatings deposited by large area filtered arc deposition

Nanocomposite TiSiN coatings were successfully synthesized at a temperature and N2 partial pressure of 350 °C and 0.02 Pa, respectively, from TiSi alloy targets with Si content of 20 at. % by using a large area filtered arc deposition technique. Scanning electron microscopy, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to investigate the surface morphology, crystalline structure, grain size, composition, and bonding structure of the deposited coatings. Nanoindentation was used to characterize the mechanical properties of the deposited coatings. It was found that adding Si into TiN coatings reduces the grain size significantly from 16.9 to 5.8 nm, changes the orientation from (111) to (220) preferred orientation, and increases the hardness and Young’s modulus from 33 and 376 GPa to 51 and 449 GPa, respectively. XPS and XRD results show that the Si/Ti atomic ratio in the coatings is 0.17 and the deposited TiSiN coatings consist of nanosized TiN grains encapsulated by amorphous Si3N4 layer, corresponding to the superhigh hardness of the TiSiN coatings. The high plasma density, ion energy, and ion reactivity of the filtered cathodic arc plasma contribute to the formation of the nanocomposite TiSiN coatings at low temperature and low N2 partial pressure.

Internal stresses in TiN/Ti multilayer coatings deposited by large area filtered arc deposition

A series of TiN/Ti multilayer coatings with fixed TiN layer thickness and different Ti layer thicknesses were deposited using a large area filtered arc deposition technique. X-ray diffraction was used to investigate the crystalline structure, lattice strain, and crystallinity of the deposited coatings. A substrate curvature method was used to measure the internal stress in the multilayer coatings. The influence of the Ti interlayer thickness on the crystalline structure and internal stress in the coatings was systematically studied. It was found that a cubic TiN phase and hexagonal Ti phase exist in all the multilayer coatings. The TiN and Ti layers in the multilayer coatings exhibit a strong (111) and (002) preferred orientation, respectively. With the increase in the Ti layer thickness, the d-spacing decreases and the peak width increases for both TiN (111) and Ti (002) peaks, indicating a decrease in the lattice strain and an increase in the crystallinity of both TiN and Ti phases. It is suggested, that the reduction in the defect density in both TiN and Ti layers and the relaxation of the stain by the diffusion of the Ti atoms in the underneath Ti layer contribute to the decrease in the total internal stress with increasing Ti layer thickness.

Thermal stability and oxidation resistance of TiCrAlYO coatings on SS430 for solid oxide fuel cell interconnect applications

Chromia-forming ferritic stainless steels are being considered for interconnect applications in planar solid oxide fuel cell (SOFC) stacks because of their low cost and physical properties. At high temperatures, ferritic steels lack environmental stability in the SOFC operating environment, and gradually degrade the cell stack performance. In this study, an effective, dense and well adherent TiCrAlYO coating was deposited on an SS430 alloy using the filtered arc deposition technique. High-energy ion backscattering was used to characterize the composition and the thermal stability of the coatings. The chromium volatility of the coated steel plates at 800 °C was also measured using ion beam analysis. Significant reductions in oxidation rates as well as reduced Cr volatility were observed for the coated alloys.

Electron field emission from diamond-like carbon films and a patterned array by using a Ti interfacial layer

Electron field emission from diamond-like carbon (DLC) films deposited on Si, Ti/Si, and Au/Si substrates by a filtered arc deposition technique was studied. As compared to DLC/Si and DLC/Au/Si, electron field emission from DLC/Ti/Si was enhanced, showing an increased emission current density and emission site density (∼1.2×103/cm2). An emission site density up to 2.2∼2.2×103/cm2 was obtained after the DLC/Ti/Si had been annealed at 430 °C for 0.5 h. A patterned DLC/Ti/Si array fabricated by the oxygen reactive ion beam etching technique showed further field emission enhancement. An emission site density up to 3.2∼3.5×103/cm2 and a threshold field as low as 2.1 V/μm were achieved. It was shown that the low potential barrier at the interface and high local geometric electric field enhancement around the edges produced by reactive ion beam etching were possible causes of the enhancing effects. It could also be explained by Geis’ metal-diamond-vacuum triple junction emission mechanism.

Dissolution and soldering behavior of nitrided hot working steel with multilayer LAFAD PVD coatings

Soldering and corrosive dissolution are the primary causes of die non-performance in permanent mold and die casting production of net shape parts for the transportation industry. At worst, these corrosive reactions result in core pin or sprue dissolution, and at the least, some soldered cast metal remains behind when the casting is ejected. The objective of this work was to explore the possibility of surface engineering of the die steel surface to reduce the dissolution and soldering tendencies of the surface. This paper presents a duplex surface treatment approach for dissolution resistance that consists of nitrided hot working die steel substrate coated by multi-layer titanium-based coatings applied by the large area filtered arc deposition technique. The dissolution behavior of the coating candidates is evaluated by measuring weight loss after dipping them in molten aluminum for a predetermined time. Results are compared with those of single layer coatings and surface treatments. The chemisorption and adhesion behavior is evaluated by measuring ejection force of the soldered material. The duplex coating is found to significantly reduce both the dissolution and adhesion tendencies of the coated steel surface.

Optical constants of tetrahedral amorphous carbon films in the infrared region and at a wavelength of 633 nm

The optical constants of tetrahedral amorphous carbon (ta-C) films in the infrared region and at a wavelength of 633 nm were investigated. The ta-C films were prepared by the filtered arc deposition technique under different carbon ion energies of 22–320 eV. The ta-C films contained high sp3 bonding of 82%–93% and had very smooth surfaces. The optical band gap was found to be controlled essentially by the presence and arrangement of the sp2 sites in the ta-C films. The real and imaginary parts, ε1 and ε2, of the dielectric constant, refractive index, n, and extinction coefficient, k, of ta-C films were determined from measurements of infrared reflection and spectroscopic ellipsometry. The results indicated that in our region of investigation ta-C films exhibited a fine transparency at a wavelength of 633 nm, especially in the infrared region. Both n and k, and consequently, ε1 and ε2, showed considerable variation in ion energy, and had minimum values approaching those of diamond for film prepared at an ion energy around 220 eV. The dependence of the optical constants on the sp3 content of ta-C films indicated that with increased sp3 content, ta-C film possessed a dielectric constant, refractive index and extinction coefficient much closer to that of diamond.

Low-temperature annealing effect on electron field emission of tetrahedral amorphous carbon films

The low-temperature annealing effect on electron field emission of tetrahedral amorphous carbon (ta-C) films was investigated. Ta-C films prepared by a filtered arc deposition technique were annealed at 400 °C for 60-120 min in a nitrogen atmosphere. The density and sp3 content in as-grown film were 3.3 g cm-3 and ~90%, respectively. After annealing, no obvious changes in film density or sp3 content were observed. The threshold electric field of electron emission of annealed ta-C films increased. Through annealing the clustering of sp2 bonded carbon would occur, resulting in bandgap reduction and the eventual increase of the emission barrier. After a given annealing period, the degree of clustering increased, and was responsible for the threshold electric field increasing further. The results implied that the control of the sp2 bonding configuration in addition to the sp3 bonding is important in obtaining good emission properties for ta-C films.

Electron field emission from a patterned diamond-like carbon flat thin film using a Ti interfacial layer

A 200-nm-thick diamond-like carbon film was prepared on Ti-deposited Si (ρ<0.01 Ω cm) using a filtered arc deposition technique. Field-emission properties of it are enhanced as compared to films deposited on Si, showing an increased current and emission site density (∼1.2×103/cm2). A patterned diamond-like carbon flat thin film on Ti-deposited Si fabricated by the oxygen reactive ion-beam etching technique shows further enhanced field-emission properties. An emission site density of 3×103/cm2 was obtained. Field emission could be observed at a field value as low as 2.1 V/μm. It is shown that the low potential barrier at the interface and high local geometric electric field enhancement around the edges produced by reactive ion-beam etching are possible causes for the enhanced effects. It can also be explained by the Geis’ metal–diamond–vacuum triple junction emission mechanism.