Pulsed Filtered Vacuum Arc Deposition Research Articles

Nanodiamond embedded ta-C composite film by pulsed filtered vacuum arc deposition from a single target

Detonation Nanodiamonds (DNDs) are known to have sp3 core, sp2 shell, small size (few nm) and are gaining importance as multi-functional nanoparticles. Diverse methods have been used to form composites, containing detonation nanodiamonds (DNDs) embedded in conductive and dielectric matrices for various applications. Here we show a method, wherein DND-ta-C composite film, consisting of DNDs embedded in ta-C matrix have been co-deposited from the same cathode by pulsed filtered cathodic vacuum arc method. Transmission Electron Microscope analysis of these films revel the presence of DNDs embedded in the matrix of amorphous carbon. Raman spectroscopy indicates that the presence of DNDs does not adversely affect the sp3 content of DND-ta-C composite film compared to ta-C film of same thickness. Nanoindentation and nanowear tests indicate that DND-ta-C composite films possess improved mechanical properties in comparison to ta-C films of similar thickness.

Microstructure and magnetic properties of FePt:Ag nanocomposite films on SiO 2/Si(1 0 0)

FePt:Ag nanocomposite films were prepared by pulsed filtered vacuum arc deposition system and subsequent rapid thermal annealing on SiO 2/Si(1 0 0) substrates. The microstructure and magnetic properties were investigated. A strong dependence of coercivity and ordering of the face-central tetragonal structure on both Ag concentration and annealing temperature was observed. With Ag concentration of 22% in atomic ratio, the coercivity got to 6.0 kOe with a grain size of 6.7 nm when annealing temperature was 400 °C.

Structure evolution, magnetic domain structures and magnetic properties of CoPt–C nanocomposite films

CoPt–C nanocomposite thin films with various carbon concentrations were prepared by a pulsed filtered vacuum arc deposition technique. Annealing was performed in vacuum for 1 h at various temperatures. The structure evolution and magnetic properties of the films were characterized by non-Rutherford backscattering spectrometry, X-ray diffraction, magnetic force microscopy and vibrating sample magnetometer. The as-deposited samples are magnetic soft with face-central-cubic phase CoPt nanocrystals encapsulated in carbon matrix. After annealing at a sufficiently high temperature, depending on the carbon composition, the CoPt nanocrystals transform to a face-centered-tetragonal phase. For the film with a particular composition of (Co 0.44Pt 0.56) 0.55C 0.45, the coercivity is observed to increase with increasing annealing temperature, up to a value of 7 kOe at an annealing temperature of 750°C, and the grain size increases from 9 to 20 nm.

Superparamagnetic Co 36C 64 granular film

Nanocomposite Co–C thin films of about 15 nm thick were prepared by pulsed filtered vacuum arc deposition. The films were characterized by X-ray photoelectron spectroscopy, non-Rutherford backscattering spectrometry, X-ray diffraction, and magnetic force microscopy. The as-deposited films were amorphous. After annealing at 350°C for 1 h in vacuum (<10 −3 Pa), the films were found to consist of nanocrystalline Co grains encapsulated in carbon. The superparamagnetism of the annealed Co 36C 64 film was demonstrated by the measurement of DC susceptibility and magnetic hysteresis using a SQUID magnetometer. The superparamagnetic relaxation blocking temperature was marked to be about 12 K by the peak of the zero-field-cooled magnetization under a field of 100 Oe. The magnetic properties of these annealed granular Co–C films transform from superparamagnetism to ferromagnetism when the Co concentration increases.

Structure, magnetic and electrical properties of soft magnetic Co–C amorphous thin films

Amorphous Co x C 1− x thin films, with x in the range of 60–75% in atomic percentage, have been prepared by pulsed filtered vacuum arc deposition. The structures of the films were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The in-plane magnetic hysteresis loops were measured by a superconducting quantum interference device magnetometer at room temperature. The electrical transport properties were measured by the four-probe technique at various temperatures ranging from 20 to 300 K. The films were found to be magnetically soft with coercivities in the range of 2 to 12 Oe, resistivities in the range of 130 to 300 μ Ω cm, and magnetic saturation flux densities in the range of 6 to 13 kG. The films also showed good thermal stability in their structural, electrical and magnetic properties upon annealing up to 200 °C in a vacuum furnace.

Field electron emission characteristics of nitrogenated tetrahedral amorphous carbon films

The electron field emission characteristics of the nitrogenated tetrahedral amorphous carbon (ta-C:N) films deposited by a pulsed filtered vacuum arc deposition system at various conditions were investigated. The wider region of N content in the films (0–21 at.%) allow us to study systematically the effects of N content and the other related parameters on field emission characteristics of the films. It was found that the field emission for both batches of ta-C:N samples depended upon the N content and this effect dominated the effects of the other parameters, such as sp 3 content, resistivity of the films, band gap of the films, and Fermi level position. The threshold field was found to first increase with increasing N content up to 5 at.%, then started to decrease up to a minimum of approximately 4 V/μm at 10 at.%. When the N content became higher than 10 at.%, the threshold field was found to increase again. Such complicated variation of the threshold field with the N content of the ta-C:N films was discussed in terms of a three-step field emission model.

Synthesis and structure of nitrogenated tetrahedral amorphous carbon thin films prepared by a pulsed filtered vacuum arc deposition

Nitrogenated tetrahedral amorphous carbon (ta-C:N) thin films have been prepared by a pulsed filtered vacuum arc deposition system at various conditions. The chemical composition and structure of the ta-C:N films were investigated by Non-Rutherford backscattering spectroscopy, Auger electron spectroscopy, Raman, and Fourier transform infrared transmission measurements. It was observed that the amount of N atoms incorporated into the ta-C:N films, as well as the fraction and size of the sp 2 clusters, increased with increasing nitrogen pressure during deposition. On the other hand, the substrate negative bias voltage has different effects on the composition and structure of the films. The N content initially rises with increasing substrate negative bias voltage and then starts to decrease as it is further increased, while the sp 2 fraction increases monotonically with the increase of negative bias voltage. No or very few CN bond exists in the films. With increasing N content the components of the single CN and disorder activated CC diminish. The compressive stress in the films is found to decrease sharply with the increase of nitrogen content, and then keep almost constant when the N content is increased further.

Magnetic properties of (Pr0.17Co0.83)69C31 nanocomposite films prepared by pulsed filtered vacuum arc deposition

Nanocomposite (Pr0.17Co0.83)69C31 thin films were prepared by pulsed filtered vacuum arc deposition. Rapid thermal annealing was performed at various temperatures in argon. The variations of the structure and magnetic properties of these films with various annealing temperatures were studied systematically. The sample annealed at 700 °C for 1 min shows a large coercivity of 5.2 kOe and a small grain size of 7.8 nm. The overall small negative ΔM of this film indicates that virtually all the Pr0.17Co0.83 grains are isolated single domain particles with only weak dipolar interactions among them. These results indicate that (Pr0.17Co0.83)69C31 nanocomposite thin films would be a promising candidate for high-density magnetic recording medium applications.

Optical properties of nitrogenated tetrahedral amorphous carbon films

The chemical composition, structural, and optical properties of nitrogenated tetrahedral amorphous carbon (ta-C:N) films deposited by a pulsed filtered vacuum arc deposition system were characterized by non-Rutherford backscattering spectroscopy, Raman spectroscopy, and ultraviolet-visible spectroscopy. It was observed that the amount of nitrogen atoms incorporated into the ta-C:N films, as well as the sp2 fraction of the films, increased with increasing nitrogen pressure PN during deposition. As a result, the optical band gap of the ta-C:N films also decreased with increasing PN. At a fixed nitrogen partial pressure of 4×10−3 Pa, the nitrogen content was found to first increase with increasing substrate negative bias voltage (−Us), up to a maximum of about 14.5 at. % at −Us of 100 and 150 V, then decreases with further increase of −Us. The sp2 fraction however increased monotonically with increasing −Us. The optical band gap of the ta-C:N films initially increased with increasing −Us, up to a maximum at a certain −Us, and then decreased with further increase in −Us. The variation of the optical band gap with the negative substrate bias voltage was discussed in terms of the different sp2-bonded carbon configurations existing in the films and the graphitization of the ta-C:N films, as indicated by the Raman and density measurement results.

Structural and electrical properties of Co xC 1− x nanogranular films prepared by pulsed filtered vacuum arc deposition

Co x C 1− x ( x=0.18, 0.25, 0.39) nanogranular films were prepared by pulsed filtered vacuum arc deposition. Subsequent thermal annealing was performed in a vacuum furnace (∼8×10 −4 Pa) at various temperatures. The microstructural evolution of the films was characterized by non-Rutherford backscattering spectrometry, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that the as-deposited films with various Co concentrations are amorphous. Upon annealing, nanocrystalline Co grains were formed, while the carbon content remained amorphous. The electrical resistance of the films was measured as a function of temperature between 20 and 300 K, using a conventional four-point probe DC technique. While the as-deposited films were metallic in the measured temperature range, annealed films showed complicated transport properties, depending on both the Co concentration and the annealing temperature. Experimental results are compared to the general predictions of theories of weak localization and/or electron–electron interaction on the metallic side of the metal-insulator transition, and thermally assisted hopping or tunneling on the insulating side of the transition.

Characterization of CoPt-C and FePt-C Nanocomposite Films Prepared by Pulsed Filtered Vacuum Arc Deposition

AbstractCoPt-C and FePt-C nanocomposite thin films were prepared by a pulsed filtered vacuum arc deposition technique. Thermal annealing was performed in vacuum at various temperatures. The dependence of the magnetic properties on the carbon fraction and annealing temperature was studied. Both x-ray diffraction and magnetic force microscopy analyses confirmed the formation of nano-crystallites of face-centered-tetragonal phase of CoPt or FePt in the carbon matrix after annealing at a sufficiently high temperature. For the film with a particular composition of Fe43Pt35C22, the coercivity and the grain size were observed to increase with increasing annealing temperature, up to a value of 3.5 kOe at an annealing temperature of 650°C, and with a grain size about 10.5 nm.

Magnetically Soft Co-C Granular-like Amorphous Thin Films With High Resistivity and High Saturation Flux Density

AbstractGranular-like amorphous CoxC1-x nanocomposite thin films, with x in the range of 60-75% in atomic percentage, have been prepared by pulsed filtered vacuum arc deposition. The structures of the films were characterized by non-Rutherford backscattering spectrometry, transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy. The in-plane magnetic hysteresis loops were measured by a superconducting quantum interference device magnetometer at room temperature. The electrical transport properties were measured by the four-probe technique at various temperatures ranging from 20 to 300 K. The films were found to be magnetically soft with coercivities in the range of 2 to 12 Oe, resistivities in the range of 130 to 300 μΩcm, and magnetic saturation flux densities in the range of 6 to 13 kG. The films also showed good thermal stability in their structural, electrical and magnetic properties upon annealing up to 200°C in a vacuum furnace.

Structural and magnetic properties of Co 65C 35 nanocomposite films prepared by pulsed filtered vacuum arc deposition

In this paper, the Co 65C 35 nanocomposite film was prepared by pulsed filtered vacuum arc deposition. Subsequent thermal annealing was performed in a vacuum furnace (∼8×10 −4 Pa) at various temperatures. The films were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and magnetic force microscopy (MFM). The magnetic properties were measured by a SQUID magnetometer. The as-deposited film was found to be amorphous and soft ferromagnets. No obvious magnetic domain structures can be observed in the MFM image, indicating the low anisotropy in the amorphous film. After annealing at a temperature between about 300°C and 350°C, the as-deposited amorphous films went through a meta-stable stage at which a cobalt carbide phase and hexagonal close-packed (hcp) crystalline cobalt co-existed. Upon increasing of annealing temperature to 400°C, the carbide phase decomposed into hcp crystalline cobalt nanograins and graphite-like carbon. Clear MFM images with obvious long-range magnetic structures can be obtained in the annealed films. The strengthened MFM images contrast implied the enhanced magneto-crystalline anisotropy owing to the nanocrystallization of Co grains within the films. The magnetic hardening was demonstrated by the round-shaped magnetic hysteresis loops.

Magnetic properties and structure evolution of amorphous Co–C nanocomposite films prepared by pulsed filtered vacuum arc deposition

The magnetic properties and structure evolution of CoxC1−x (x=44, 65, 71 at. %) nanocomposite films prepared by pulsed filtered vacuum arc deposition were studied. The as-deposited films consist of amorphous Co clusters in a-C and are soft ferromagnets. The low coercivity in the amorphous films is due to the very low anisotropy of the amorphous Co clusters. After annealing in vacuum at 350 °C for 1 h, the Co clusters crystallize and these films become magnetically harder. The magnetic hardening is attributed to the enhanced magnetic anisotropy of the nanocrystals. Their saturation magnetization reduces slightly. This is attributed to the reduction of the density of states at the Fermi level caused by the crystallization of the amorphous Co clusters.

Microstructure evolution, magnetic domain structures, and magnetic properties of Co–C nanocomposite films prepared by pulsed-filtered vacuum arc deposition

Co-based nanocrystals encapsulated in carbon have potential applications in ultra-high-density magnetic recording media. In this work, CoxC1−x (x=60, 65, and 70 at. %) nanocomposite films were prepared by pulsed-filtered vacuum arc deposition. Subsequent thermal annealing was performed in vacuum at various temperatures. The films were characterized by non-Rutherford backscattering spectrometry, transmission electron microscopy, Raman spectroscopy, atomic-force microscopy, and magnetic-force microscopy. The as-deposited films were found to be amorphous. After annealing at appropriate temperatures, the films were found to be consisting of hexagonal close-packed nanocrystalline Co grains encapsulated in graphite-like carbon. Clear magnetic-force microscopy images were only observed in those films annealed at sufficiently high temperatures, indicating that there was perpendicular magnetic anisotropy in these films. The magnetic hysteresis loops of the films were measured by a superconducting quantum interference device magnetometer. The optimum annealing temperature for the maximum coercivity was found to depend on the cobalt concentration. For a Co65C35 sample about 20 nm thick after annealing at 350 °C in vacuum for 1 h, the saturation magnetization was 500 emu/cm3, the coercivity was 460 Oe, and the ratio of the remanence to the saturation magnetization was 0.68 at 300 K. Our results are consistent with those of the sputtered Co–C films recently reported in the literature.

Superparamagnetic Behavior of Granular Co-C Films Consisting of Nanocrystalline Cobalt Encapsulated in Carbon

ABSTRACTNanocomposite Co-C thin films of about 15 nm thick were prepared by pulsed filtered vacuum arc deposition. The films were characterized by x-ray photoelectron spectroscopy, non-Rutherford backscattering spectrometry, x-ray diffraction, magnetic force microscopy and magnetic measurements. The as-deposited films were amorphous. After annealing at 350°C for one hour in vacuum (&lt; 10−3 Pa), the films were found to consist of nanocrystalline Co grains encapsulated in carbon. The superparamagnetism of the annealed Co36C64 film was demonstrated by the measurement of DC susceptibility and magnetic hysteresis using a SQUID magnetometer. The superparamagnetic relaxation blocking temperature was marked to be about 12K by the peak of the zero-field-cooled magnetization under a field of 100 Oe. The magnetic properties of these annealed granular Co-C films transform from superparamagnetism to ferromagnetism when the Co concentration increases.