Microstructure and thickness dependent magnetic properties of nanogranular Co-Zn-O thin films for microwave applications

Co-based granular thin films with in-plane anisotropy were deposited on Si substrate by magnetron sputtering. The films have a phase structure of Co nanocrystallites and amorphous Zn-O inter-granular phases. The Co nanograins with uniform size of 8-10 nm are evenly distributed in the amorphous matrix. This structure gives the films relatively high resistivities. The as-deposited films with thickness larger than 100 nm have low coercivity (<10 Oe) along both easy and hard directions. The dynamic properties in the frequency range up 5 GHz for the films with various thicknesses have been investigated. High values of permeability (μ′ up to 560 and μ″ up to 1000) and ferromagnetic resonance frequency (FMR) up to 4.1 GHz have been obtained in these films. The FMR frequency decreases with increasing thickness, because of the increases in real and imaginary permeabilities. The high frequency characteristics have complicated dependences on the resistivity, anisotropy field, and magnetization. The microwave properties of Co-Zn-O films can be adjusted in a relatively wide range by changing film thickness, which makes these films promising for absorber applications.     

Exploring the potential of high power impulse magnetron sputtering for growth of diamond-like carbon films

Amorphous carbon films are deposited employing high power impulse magnetron sputtering (HiPIMS) at pulsing frequencies of 250 Hz and 1 kHz. Films are also deposited by direct current magnetron sputtering (dcMS), for reference. In both HiPIMS and dcMS cases, unipolar pulsed negative bias voltages up to 150 V are applied to the substrate to tune the energy of the positively charged ions that bombard the growing film. Plasma analysis reveals that HiPIMS leads to generation of a larger number of ions with larger average energies, as compared to dcMS. At the same time, the plasma composition is not affected, with Ar⁺ ions being the dominant ionized species at all deposition conditions. Analysis of the film properties shows that HiPIMS allows for growth of amorphous carbon films with sp³ bond fraction up to 45% and density up to 2.2 g cm^− 3. The corresponding values achieved by dcMS are 30% and 2.05 g cm^− 3, respectively. The larger fraction of sp³ bonds and mass density found in films grown by HiPIMS are explained in light of the more intense ion irradiation provided by the HiPIMS discharge as compared to the dcMS one.     

Effect of hydrogen flow on the properties of hydrogenated amorphous carbon films fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition

The hydrogenated amorphous carbon films (a-C:H, so-called diamond-like carbon, DLC) have exceptional physical and mechanical properties and have wide applications. In the present study, amorphous hydrogenated carbon films (a-C:H) have been deposited on a Si (100) substrate at different hydrogen flow using electron cyclotron resonance chemical vapor deposition (ECR-CVD). The flow of hydrogen changed from 10 sccm to 40 sccm and the flow of acetylene was fixed at 10 sccm. The microstructure and properties of the a-C:H were measured using visible Raman spectra, Fourier transform infrared (FTIR) spectroscopy, UV-VIS spectrometer,surface profilometer and nano-indentation. The results showed that the sp³ content and sp³-CH₂ structure in the amorphous hydrogenated carbon films increased with the hydrogen flow. The deposition rate decreased with the hydrogen flow. The residual stress and the nano-hardness of the amorphous hydrogenated carbon films increased with the hydrogen flow. Consequently, the a-C:H film become more diamond-like with the increase of hydrogen flow.     

Hexagonal diamond formation on steel substrates by negative bias microwave plasma enhanced chemical vapor deposition

This paper reports for the first time the synthesis of hexagonal diamond thin films on high-speed steel substrates by multi-mode microwave plasma enhanced chemical vapor deposition. Before deposition of the films, the substrate surface was treated by scratching with diamond powder. The deposited films were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy. The XRD patterns of (100) and (101) planes and the Raman peaks at ~ 1317-1322 cm^− 1 were observed, confirming the formation of hexagonal diamond phase in the prepared films. The effects of voltage bias on the phase formation, microstructure and hardness of the films were also studied by setting the voltage to 0, − 70, − 150 and − 190 V. The highest hardness of 23.8 GPa was found in the film having clusters of size about 550 nm deposited under a bias voltage of − 150 V. These clusters were built up of grains of size about 14 nm.     

X-ray reflectivity studies on DLC films deposited by microwave ECR CVD: Effect of substrate bias

Diamond like carbon (DLC) films were deposited at room temperature on Si (111) substrates by microwave electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) process using plasma of methane diluted with argon gas. During deposition, dc self bias (− 25 V to − 200 V) on substrate was varied by application of RF power to the substrate. The influence of substrate bias on density of the deposited films was studied by X-ray reflectivity (XRR). The results from these measurements are further correlated with the results from UV and visible Raman spectroscopy. DLC film is modeled as a structure having three different layers such as low density surface, bulk and interface with the substrate. This three-layer model is used to fit the measured XRR data to evaluate the surface, interface and interlayer roughness, thickness and density of these films. The surface roughness obtained from XRR is correlated with the results from Atomic Force Microscopy (AFM) measurements. The observed results are explained based on the subplantation model for DLC film growth.     

Study of growth processes and mechanical properties of nanoscale multilayered C/C films

The growth processes of carbon films deposited using two techniques (sputtering and RF plasma assisted chemical vapor deposition, PACVD), and the effects of stacking these films in a multilayered structure on their mechanical and adhesion properties were studied. The films deposited by the two techniques differed in composition, structure and hardness. They are termed “hard C” and “soft C” according to their synthesis process, sputtering and PACVD respectively. By means of stress measurements and angle-resolved X-ray photoelectron spectroscopy, the growth mechanism of the films was characterized when they were deposited on a silicon substrate and when one kind of carbon film was deposited onto the other kind, in order to simulate a multi-layer film formation. This study evidenced the effect of converting the individual layer surfaces into interfaces when building a multilayer film. On one hand, this conversion appeared to increase the compressive stress of the multilayer films for the lowest periodicity (14 nm and 7 nm of half-period). On the other hand, a strong correlation between the stress resulting from multilayering and the film elasto-plastic properties was found. A hardening effect, put in evidence by applying a nano-indentation “plasticity index”, was obtained for the most layered films (i.e. with the lowest modulation period) and this effect is discussed in relation with the existing models for multi-layer strengthening. The film adhesion to polyethylene terephtalate (PET) substrates was investigated. A beneficial effect of multi-layering on film adhesion was significant only when the half-width period went down to 14 nm and 7 nm. The adhesion improvement cannot be related to a reduced internal stress, since the most stressed films were also the most adherent. Instead the compressive stress found in the films with the lowest periodicity is thought to induce a stronger bonding of the soft C layer (polymer-like) to the PET substrate and to the hard C layers, through chain entanglement across the interface.     

Structure and mechanical properties of nickel/carbon nanocomposite films formed by microwave plasma-assisted deposition technique from argon-acetylene gas mixture

The structure and mechanical properties of nickel/hydrogenated amorphous carbon (Ni/a-C:H) films formed by microwave plasma-assisted deposition technique were investigated as a function of the carbon content using various methods: Rutherford backscattering spectroscopy (RBS), Raman spectroscopy and tribometry. The size of carbon clusters determined by Raman spectroscopy in Ni/a-C:H films deposited in gas mixtures containing 40 and 60% of C₂H₂, and in nickel free a-C:H films was 1 and 4 nm, respectively. However, the amorphous Ni/a-C:H films deposited from a gas mixture containing 60% of C₂H₂ exhibited the lowest friction coefficient (∼ 0.04), at the same time the nanohardness of these films was ∼ 7 GPa.     

Cathodic arc plasma deposition of nano-multilayered ZrN/AlSiN thin films

Thin films of ZrN/AlSiN were deposited on SKD 11 tool steel substrate using Zr and AlSi cathodes in an Ar/N₂ gas mixture in a cathodic arc plasma deposition system. The influence of the AlSi cathode arc current and the substrate bias voltage on the mechanical and structural properties of the films was investigated. X-ray diffraction, electron probe micro-analysis, high resolution transmission electron microscopy, nanoindentation and profilometry were used to characterize the films. The ZrN/AlSiN thin films had a multilayered structure by rotating the substrate in which nano-crystalline ZrN layers alternated with amorphous AlSiN layers. The hardness of the films increased as the AlSi cathode arc current was raised from 35 to 40 A, and then decreased with a further increase of the current. The hardness of the films increased with the increase of the bias voltage from − 50 to − 100 V. Further increase in the bias voltage decreased the hardness. The films exhibited a maximum hardness of 38 GPa. With the increase of bias voltage, the residual stress of the films correlated well with the hardness.     

Corrosion protection of ultra-thin ta-C films for recording slider applications at varied substrate bias

Ultra-thin tetrahedral amorphous carbon (ta-C) films have been prepared by filtered catholic vacuum arc system for recording slider applications. In order to study the corrosion behavior of the slider coatings deposited at different substrate bias, the micro-structure and surface properties of the ta-C films were respectively investigated in terms of Raman spectroscopy, atomic force microscopy, water contact angle and corrosion measurements. Results showed that a very smooth ta-C film with lowest surface energy and highest sp³ bonding content was obtained at the medium bias voltage of 100 V. However, as to the protection against corrosion, the optimum bias was found to be greater than that giving the maximum diamond-like properties.     

Influence of growth temperature on the optical and structural properties of ultrathin ZnO films

This study investigates the effect of growth temperature on the optical and structural properties of ultrathin ZnO films on the polished Si substrate. Thickness of the ultrathin ZnO films deposited by atomic layer deposition (ALD) method was about 10 nm. Photoluminescence (PL), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques were used to measure the properties of ultrathin ZnO films. Experimental results showed that the ultrathin ZnO film deposited at 200 °C had excellent ultraviolet emission intensity, and the average roughness of the film surface was about 0.26 nm.     

Characteristics and tribological performance of DLC and Si-DLC films deposited on nitrile rubber

The characteristics and tribological performance of DLC and Si-DLC films with and without Si–C interlayers were studied in this paper. The films were deposited on nitrile rubber using a closed field unbalanced magnetron sputtering ion plating system. The film properties and characteristics were determined by scanning electron microscopy (SEM), hydrophobicity studies, Raman spectroscopy and tribological investigations. Tribological performance of these films was investigated using a pin-on-disc tribometer under applied loads of 1 N and 5 N under conditions of dry and wet sliding. The effect of immersing the films in water on tribological performance was also examined. The results show that the morphology of the films had a crack-like network. At a substrate bias of − 30 V, the coatings were characterised by a very dense non-columnar microstructure. The highest value of the ratio of intensities of the D and G peaks (I_D/I_G) was 1.2 for Si-DLC film with Si–C interlayer. The lowest value of 0.7 was observed for DLC film. The contact angle (CA) of water droplets showed that the films were hydrophobic. These results are interpreted in terms of hybridisation of carbon in these coatings. The tribological investigation showed a dependence on both the tribological condition under investigation and the atomic percentage of Si in the films. At 5 N normal load the lowest wear depth was observed for DLC films.     

The effect of applied substrate negative bias voltage on the structure and properties of Al-containing a-C:H thin films

Al-containing hydrogenated amorphous carbon (Al-C:H) films were prepared using a magnetron sputtering Al target in the CH₄ and Ar mixture atmosphere with various applied substrate pulse negative bias voltages. The hydrogen content and internal stress of the film decrease dramatically with the substrate pulse bias voltage increase. However, the hardness values of the films keep at high level (∼ 20 GPa) without any obvious changes with the increase of the applied substrate pulse bias voltages. The Al-C:H film prepared at applied substrate high bias voltage shows a long wear life and low friction coefficient.     

Deposition of nanolayered CrN/AlBN thin films by cathodic arc deposition: Influence of cathode arc current and bias voltage on the mechanical properties

Thin films of CrAlBN were deposited on SKD 11 tool steel substrate using Cr and AlB cathodes in a cathodic arc plasma deposition system. The influence of AlB cathode arc current and substrate bias voltage on the mechanical and the structural properties of the films was investigated. The CrAlBN thin films had a multilayered structure in which the nano-crystalline CrN layer alternated with the amorphous AlBN layer. The hardness of the films increased as the AlB cathode arc current was raised from 35 to 45 A, and then decreased with further increase of the current. The hardness of the films increased rapidly with the increase of the bias voltage from − 50 to − 150 V. Further increase in the bias voltage decreased the hardness. The maximum hardness of 48 GPa was obtained at the bias voltage of − 150 V. With the increase of bias voltage, a good correlation between the residual stress and the hardness of the films was observed.     

UNCD/a-C nanocomposite films for biotechnological applications

Ultrananocrystalline diamond/amorphous carbon nanocomposite films (UNCD/a-C) have been deposited by microwave plasma chemical vapor deposition from a 17% CH₄/N₂ mixture. The films consist of diamond nanocrystallites of 3-5 nm embedded in an amorphous carbon matrix of 1-1.5 nm width. In a first series of experiments it is shown that as-grown UNCD/a-C films are hydrogen-terminated, conductive and very stable. Furthermore, by plasma- and photochemical treatments the H-termination can either be improved or replaced by terminating OH or F functionalities, whereas chemical room temperature processes to change the termination failed. A second set of investigations concerns the functionalization of differently terminated UNCD surfaces. Processes are discussed to bind DNA on H-terminated UNCD and to deposit an anti-fouling poly(ethylene glycol) layer on OH-terminated films. A third series of experiments shows that UNCD surfaces are not prone to unspecific interactions with highly-fouling proteins such as bovine serum albumin (BSA) but nevertheless some interaction will take place. However, the amount of adsorption and also the ratio of BSA and fibrinogen adsorption, which is of importance for the hemocompatibility of a surface, can be adjusted by the surface termination. Finally, it will be shown that continuous as-grown UNCD surfaces are bioinert and not cytotoxic for a variety of different cell lines.     

Influence of bias on properties of carbon films deposited by MCECR plasma sputtering method

The mirror-confinement-type electron cyclotron resonance(MCECR) plasma source has high plasma density and high electron temperature. It is quite useful in many plasma processing, and has been used for etching and thin-film deposition. The carbon films with 40 nm thickness were deposited by MCECR plasma sputtering method on Si, and the influence of substrate bias on the properties of carbon films was studied. The bonding structure of the film was analyzed by the X-ray photoelectron spectroscopy(XPS), the tribological properties were measured by the pin-on-disk(POD) tribometer, the nanohardness of the films was measured by the nanoindenter, and the deposition speed and the refractive index were measured by the ellipse meter. The better substrate bias was obtained, and the better properties of carbon films were obtained.     

In situ accelerated micro-wear — A new technique to fill the measurement gap

A novel accelerated microtribological capability was implemented on a commercial ultra-low drift nanomechanical test system (NanoTest) by modification of the instrument's hardware. 10 and 25 μm spheroconical and Berkovich diamond probes were used in this study. To compare the accelerated micro-wear capability with existing nano-scratch tests, a range of thin film samples previously characterised were evaluated, including 80 nm ta-C film deposited on Si, 150 nm a-C:H thin film deposited on Si, metal-containing molybdenum disulphide (MoST) 70-150 nm, 70 nm a-C:H and 1 μm a-C films deposited on Si, multilayered 20 nm Si3N4/20 nm NiCr/80 nm Si3N4 multilayer coating deposited on float glass and additionally bulk Cu sample. Operational principles of the experimental setup are explained and reliability of the method is validated with a number of experiments. Results are presented and discussed following four experimental sections of this paper: (i) constant load micro-wear of various films on Si, (ii) constant load micro-wear kinetics of bulk Cu, (iii) ramped load micro-wear of thin films and (iv) tangential force calibration.     

Plasma biasing to control the growth conditions of diamond-like carbon

It is well known that the structure and properties of diamond-like carbon, and in particular the sp³/sp² ratio, can be controlled by the energy of the condensing carbon ions or atoms. In many practical cases, the energy of ions arriving at the surface of the growing film is determined by the bias applied to the substrate. The bias causes a sheath to form between substrate and plasma in which the potential difference between plasma potential and surface potential drops. In this contribution, we demonstrate that the same results can be obtained with grounded substrates by shifting the plasma potential. This “plasma biasing” (as opposed to “substrate biasing”) is shown to work well with pulsed cathodic carbon arcs, resulting in tetrahedral amorphous carbon (ta-C) films that are comparable to the films obtained with the conventional substrate bias. To verify the plasma bias approach, ta-C films were deposited by both conventional and plasma bias and characterized by transmission electron microscopy (TEM) and electron energy loss spectrometry (EELS). Detailed data for comparison of these films are provided.     

高功率等离子磁控溅射法制备含钛类金刚石碳膜(英文)

为了改善类金刚石碳膜的性能,采用高功率等离子磁控溅射法将含钛非晶碳薄膜沉积在304不锈钢基材上,气源为C2H2-Ar混合气体,金属钛为阴极靶材。为了改善附着力和降低残余应力,制备了含Ti/TiC/DLC多层结构的镀膜。利用GDS、XRD、SEM、Raman光谱法、纳米压痕仪和盘-销摩擦计研究基材偏压及基材与靶材的距离对薄膜性能的影响。结果表明,薄膜具有优良的粘合强度和韧性。     

Microstructure and tribological properties of the a-C:H films deposited by magnetron sputtering with CH4/Ar mixture

Hydrogenated amorphous carbon (a-C:H) films were deposited on steel and silicon wafers by unbalanced magnetron sputtering under different CH₄/Ar ratios. Microstructure and properties of the a-C:H films were investigated via Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Atomic force microscopy (AFM) and substrate curvature method. The results revealed that CH₄/Ar ratio played an important role in the H content but acted a little function on the sp³/sp² ratio of the films. Also, the internal stress of those films was relatively low (< 1 GPa), and the deposition rate decreased firstly and then increased with the decrease of the CH₄ fraction. The film deposited under CH₄/Ar = 1/1 (55 sccm/55 sccm) with moderate sp³ C-H / sp³ C-C had the best tribological properties. The composition, microstructure and properties of the a-C:H films were strongly dependent on the deposition process and composition of reactant gases.     

Adhesion improvement of hydrogenated diamond-like carbon thin films by pre-deposition plasma treatment of rubber substrate

For reduction of friction and enhancement of wear resistance of dynamic rubber seals, thin films of hydrogenated diamond-like carbon (DLC) have been deposited on hydrogenated nitrile butadiene rubber (HNBR) via magnetron-enhanced plasma chemical vapor deposition (ME-PCVD). Pre-deposition plasma treatment of HNBR substrate is proved to be crucial for the improvement of film performance due to enhanced interfacial adhesion. The columnar structure and the crack network formed during deposition enhance the flexibility of DLC thin films and exhibit strain tolerance up to 5%. Below 50% stretch strain and after unloading, thin DLC films of ∼ 300 nm thickness still adhere on the rubber substrates and no spallation or delamination is observed. The thin DLC film deposited on Ar-plasma pre-treated rubber at − 400 V substrate bias potential exhibits a very low coefficient of friction of 0.175 (compared to > 1 of uncoated HNBR rubber). After tribotests even under high normal load of 3 N, almost no wear can be seen on the films. Such tribological property is even better than that of 1 µm thick DLC or Me-DLC coated rubbers.