Cathodic Arc Process Research Articles

DETERMINATION OF DENSITY-OF-STATES OF NANOCLUSTER CARBON THIN FILMS MIS STRUCTURE USING CAPACITANCE–VOLTAGE TECHNIQUE

Nanocluster carbon thin films (NC) were deposited at room temperature by cathodic arc process. These films were clustered, amorphous and disordered in nature which is verified using Raman spectroscopy. Density of defect states (DOS), which influences electronic and optical properties, were determined from the capacitance–voltage (C–V) characteristic of Al / NC / c - Si metal–insulator–semiconductor (MIS) structure near the Fermi level of undoped samples. Dielectric constant of the films was also estimated using the same technique. The DOS were found to be varying from 5.68 × 1016 to 4.9 × 1019 cm-3. The dielectric constant varied between 2.76 to 11.8.

Effect of TiAlN PVD coatings on corrosion performance of WC–6%Co

The present study has been carried out to evaluate the corrosion performance of three different (Ti1–xAlx)N/TiN multilayers coatings commercially deposited on WC–Co inserts. Two of these coatings were nanostructured, and all of them presented different Ti/Al atomic ratios varying from 2 : 3 up to 7 : 3 and were deposited by employing a commercial physical vapour deposition cathodic arc process. X-ray diffraction analysis indicated that the grain size for both the TiAlN and TiN layers in the coatings architecture, varied between approximately 9 to 14 nm. The corrosion performance was evaluated in a 3 wt-%NaCl solution using both open circuit potential and potentiodynamic polarisation measurements. Scanning electron microscopy and energy dispersive spectroscopy surface characterisation before and after corrosion testing allowed the determination that all the coatings under study show a corrosion current density of approximately one order of magnitude smaller than the uncoated substrate, indicating thus their beneficial effect from the corrosion protection viewpoint.

Effect of high substrate bias and hydrogen and nitrogen incorporation on spectroscopic ellipsometric and atomic force microscopic studies of tetrahedral amorphous carbon films

The influence of substrate bias and hydrogen/nitrogen incorporation on the optical properties [studied by spectroscopic ellipsometry (SE)] and surface morphology [studied by atomic force microscopy] of tetrahedral amorphous carbon (ta-C) films, deposited by S bend filtered cathodic vacuum arc (FCVA) process, is reported. SE spectra of the imaginary part of the dielectric constant are used to estimate carbon bonding ratios. In ta-C films, optical constants increase with substrate bias and hydrogen/nitrogen incorporation. The optical band gap (Eg) and sp3 content increase up to −200V substrate bias and then decrease. Eg increases with hydrogen incorporation but is unchanged by nitrogen incorporation.

Non-enzymatic glucose detection using nitrogen-doped diamond-like carbon electrodes modified with gold nanoclusters

Highly sensitive electrochemical electrodes for glucose detection were developed by using Au nanoclusters (NCs) to modify nitrogen-doped diamond-like carbon thin films (DLC:N/Au). The DLC:N/Au electrodes were prepared with a filtered cathodic vacuum arc process followed by electrodeposition and characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy. The size of the Au NCs covered by Au oxide ranged between 10 and 70 nm with a density of 108–109 clusters per cm2. Glucose oxidation at the DLC:N/Au electrodes started from about –0.5 V due to the high catalytic activities of the Au NCs in NaOH solutions, and the catalytic ability of the electrodes depended on the amount of Au NCs deposited on the electrode surfaces. A linear detection range of glucose with the DLC:N/Au electrodes was identified from about 0.25 to 30 mM (covering blood glucose levels in diabetic patients) with a detection limit of 60 μM. The experimental results showed that the non-enzymatic glucose sensors based on the DLC:N/Au electrodes had high sensitivity and good reproducibility and stability.

Effect of high substrate bias and hydrogen and nitrogen incorporation on density of states and field-emission threshold in tetrahedral amorphous carbon films

This article reports the influence of substrate bias during growth and of hydrogen and nitrogen incorporation on density of states [N (EF)] and field-emission threshold (Eturn-on) in tetrahedral amorphous carbon (ta-C) films, deposited using an S-bend filtered cathodic vacuum arc process. The variation in negative substrate bias from −20 to −200 V was found to initially lead to a small decrease in N (EF) and Eturn-on, and a small increase in the emission current density (J) at 12.5 V/μm in the case of as-grown ta-C films; beyond −200 V substrate bias there is a reversal in the trend. The values of N (EF)=1.3×1017 cm−3 eV−1, Eturn-on=8.3 V/μm, and J=6.19 mA/cm2 were observed at −200 V substrate bias. However at −300 V the properties were not very different from those at −200 V substrate bias and so with a view to use the higher energy, hydrogen and nitrogen incorporation studies were carried out in this condition. It was observed that there was further enhancement in properties with hydrogen and nitrogen incorporation. The best properties measured with in the range of hydrogen and nitrogen incorporation in the present study were N (EF)=8.0×1016 cm−3 eV−1, Eturn-on=7.6 V/μm, and J=23.7 mA/cm2, respectively.

Properties of boron and phosphorous incorporated tetrahedral amorphous carbon films grown using filtered cathodic vacuum arc process

This paper reports the electrical, mechanical, structural and field emission properties of as grown and also boron and phosphorous incorporated tetrahedral amorphous carbon (ta-C) films, deposited using a filtered cathodic vacuum arc process. The effect of varying boron and phosphorous content (up to 2.0 at.% in to ta-C) on the conductivity ( σ D), activation energy (Δ E 1), hardness, microstructure, emission threshold ( E turn-ON) and emission current density ( J) at 12.5 V/μm of ta-C: B and ta-C: P films deposited at a high negative substrate bias of −300 V are reported. It is observed that both boron and phosphorous incorporation leads to a nearly an order increase in σ D and corresponding decrease in Δ E 1 and a slight increase in hardness as compared to as grown ta-C films. In the case of field assisted electron emission, it is observed that E turn-ON increases and J decreases. The changes are attributed to the changes in the sp 3/sp 2 ratio of the films due to boron and phosphorous incorporation. The effect of boron on ta-C is to give a p-type effect whereas the effect of phosphorous gives n-type doping effect.

Characterization of Boron- and Phosphorous-Incorporated Tetrahedral Amorphous Carbon Films Deposited by the Filtered Cathodic Vacuum Arc Process

This paper reports the X-ray photoelectron spectroscopy (XPS), X-ray-induced Auger electron spectroscopy (XAES), and Raman studies of boron- and phosphorous-incorporated tetrahedral amorphous carbon (ta-C) films deposited by the filtered cathodic vacuum arc process. A systematic study of the influence of varying boron (B) and phosphorous (P) content on the properties of the as-grown ta-C films deposited at high negative substrate bias (-300 V) is reported by analyzing the C 1s, B 1s, and P 1s core levels using photoelectron spectroscopy. The sp3 and sp2 contents in the films were determined by measuring the width of the X-ray-induced Auger peaks. B incorporation in ta-C films up to 2.0 at. % increases the sp2 content and decreases the sp3 content by 3.6%, whereas P incorporation up to 2.0 at. % results in an increase of sp2 content and decrease of sp3 content by ∼ 30%. The valence band spectra show changes in the Fermi level as B and P are incorporated into the ta-C films. The characteristic Raman spectra confirm the high sp3 content in the deposited films. Thus, the study demonstrates, in the case of high negative substrate bias films, that a pronounced decrease in sp3 fraction or the diamond-like nature of the ta-C films occurs upon P incorporation in comparison to that upon B incorporation.

Effect of Silane Flow Rate on Structure and Corrosion Resistance of Ti–Si—N Thin Films Deposited by a Hybrid Cathodic Arc and Chemical Vapour Process

Ti–Si–N thin films with different silicon contents are deposited by a cathodic arc technique in an Ar+N2 +SiH4 mixture atmosphere. With the increase of silane Bow rate, the content of silicon in the Ti–Si–N films varies from 2.0 at. % to 12.2 at. %. Meanwhile, the cross-sectional morphology of these films changes from an apparent columnar microstructure to a dense fine-grained structure. The x-ray diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) results show that the Ti–Si–N film consists of TiN crystallites and SiNx amorphous phase. The corrosion resistance is improved with the increase of silane Bow rate. Growth defects in the films produced play a key role in the corrosion process, especially for the local corrosion. The porosity of the films decreases from 0.13% to 0.00032% by introducing silane at the Bow rate of 14sccm.

ANALYSIS OF CLUSTER DIMENSION AND MORPHOLOGY OF ROOM TEMPERATURE GROWN NANOCARBON USING CATHODIC ARC AND ITS INFLUENCE ON FIELD ASSISTED ELECTRON EMISSION

Low temerpatuere grown nanocluster carbon thin films grown using a continuous cathodic arc process at room temperature are found to be interesting material for wide range of and nanoelectronic application. Reported is the study of the influence of background gases such as helium and nitrogen on the nanoclsuter dimension and morphology and a possible influence of the -4 same to field assisted electron emission properties. The Helium partial pressure was changed from 5x10 to 50 Torr under two -4 -3 different nitrogen partial pressure conditions namely 1x10 Torr and 1x10 Torr respectively. Raman and SEM data for these samples were used to estimate the cluster dimension structural and morphological properties. The surface morphology of the films grown, varied from atomic smooth surface to clusters with varying sizes (50–200 nm). A methodology for the estimation of cluster dimension from the Raman data was established and the estimated data compared with dimensions derived from SEM images. Effort was made to look at the possible correlation of between process parameters, estimated parameters and field assisted electron emission data. The curve fitting analysis and the observed correlation, indicates possibility of establishing Raman Spectroscopy as an instantaneous characterization approach for the evaluation of nanocarbons.

Alignment and switching behaviors of liquid crystal on a-SiOx thin films deposited by a filtered cathodic arc process

A new method is described for the preparation of silicon oxide layers, which produces vertical alignment of liquid crystal with controlled pretilt angles, by a reactive filtered cathodic arc deposition under oblique incidence geometry. The pretilt angle is dependent on the angle of deposition, but is not simply caused by the surface roughness. The achievable pretilt angle by this method is ∼5.5°, which allows uniform switching behavior under an applied electric field.

Electrochemical performance of diamond-like carbon thin films

Diamond-like carbon (DLC) thin films used in this study were intended for their electrochemical properties. The DLC films were deposited by a filtered cathodic vacuum arc (FCVA) process on p-type silicon (100) substrates biased at different pulse voltages (0–2000 V). The chemical bonding structures of the DLC films were characterized with micro-Raman spectroscopy and the electrochemical properties were evaluated by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The DLC films showed high impedance, high polarization resistance and high breakdown potential in a 0.5 M H 2SO 4 aqueous solution, which were attributed to the high sp 3 content and uniformity of the films. The excellent chemical inertness of the DLC films made them promising corrosion resistant coating materials.

Molybdenum disulfide as a lubricant and catalyst in adaptive nanocomposite coatings

Nanocomposite YSZ–Ag–Mo–MoS 2 coatings with different MoS 2 additions (0–100 at.%) were deposited with a hybrid pulsed laser/magnetron sputtering/filtered cathodic arc process. Wear testing was performed from 25 to 700 °C for each of the coatings. Electron microscopy and other characterization techniques were used to examine the surfaces and wear tracks of the coatings and to determine the mechanisms resulting in the measured tribological properties. Adaptive coatings containing 8 at.% MoS 2 demonstrated a friction coefficient of 0.2 throughout the temperature range examined here, compared to 0.4 for YSZ–Ag–Mo with no MoS 2. Characterization of the YSZ–Ag–Mo–8% MoS 2 coating revealed that MoS 2 and silver provided lubrication at temperatures ≤ 300 °C, while silver molybdate phases and MoO 3 were effective lubricants at higher temperatures. Silver molybdate was not observed in the coatings containing 0% MoS 2. The role of sulfur in the formation of silver molybdate is briefly discussed.

Use of silane for the deposition of hard and oxidation resistant Ti–Si–N coatings by a hybrid cathodic arc and chemical vapour process

Ti–Si–N coatings were deposited on M2 steel substrates using a hybrid cathodic arc and chemical vapour deposition process. Silane was used as the silicon precursor. Whatever the films silicon content, only TiN grains were detected by X-ray diffraction. The mean grain size was estimated to be lower than 10 nm. The silicon content strongly influenced the TiN preferred orientation. Depth sensing indentation showed that films with Si/Ti = 0.08 exhibited a hardness close to 43 GPa. Silicon addition into TiN-based coatings induced an improvement of their oxidation resistance. The film properties were comparable to those obtained for Ti–Si–N coatings deposited using a Ti–Si target, indicating that the hybrid process was suitable for the deposition of hard and oxidation resistant Ti–Si–N coatings.

Reflectance and photoluminescence spectra of as grown and hydrogen and nitrogen incorporated tetrahedral amorphous carbon films deposited using an S bend filtered cathodic vacuum arc process

The study of reflectance and photoluminescence (PL) spectra of as grown and also hydrogen and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films, deposited using an S bend filtered cathodic vacuum arc process is reported here. First the effect of negative substrate bias on the properties of as grown ta-C films and next the effect of varying hydrogen and nitrogen partial pressure at a high substrate bias of −300 V on the properties of hydrogen and nitrogen incorporated ta-C (ta-C:H and ta-C:N) films are reported for the first time. The values of the optical band gap (Eg) evaluated using the reflectance spectra were found to decrease with the increase of the substrate bias in the as grown ta-C films. Hydrogen incorporation up to 1.9×10−2 Pa partial pressure in as grown ta-C films increased the values of Eg and beyond which the values of Eg decreased while the nitrogen incorporation up to 3.0×10−1 Pa partial pressure has no effect on the Eg values. The PL spectra indicated a strong peak at ∼2.66 eV in as grown ta-C films deposited at −20 V substrate bias. This main peak was found to shift to higher energy with the increase of the substrate bias up to −200 V and thereafter the PL peak shifted towards the lower energy. Other peak at 3.135 eV starts appearing and this is found to start shifting to higher energy for films deposited at higher substrate bias. The intensity of the main PL peak was enhanced at low temperature and several other peaks started appearing in place of the broad peak at ∼3.16 eV. The peak width and area of both the main peak were found to decrease with the increase of substrate bias in as grown ta-C films and with the increase of the hydrogen and nitrogen partial pressure used in depositing ta-C:H and ta-C:N films. The current models on the source of luminescence in amorphous carbon have been discussed.

Comparison of hydrogenated and unhydrogenated carbon films obtained by FCVA onto Ti6Al4V: Structure, hardness and biocompatibility study

This work compares hydrogenated and unhydrogenated carbon films as surfaces for implants. Thin films are deposited by a filtered cathodic vacuum arc (FCVA) process in a variable methane pressure in order to obtain very close sets of deposition conditions for the hydrogenated and unhydrogenated films. Ti6Al4V alloy is used as substrate. The structure is investigated by XRR, ERDA-RBS and Raman spectroscopy. The mechanical and physico-chemical properties such as adherence load, hardness and wettability are studied for the two sets of coatings on the metallic substrate. The biological approach is a study of the cytocompatibility of these films with MC3T3-E1 osteoblast-like cells and in particular the adhesion kinetics. The carbon coatings influence neither the morphology nor the early adhesion behaviour of these target cells on the substrates. This is probably due to similar hydrophilic surface energies of the tested control and carbon-coated test samples.

Characterisation of Titanium Nitride Thin Films Deposited by Cathodic Arc Plasma Technique on AISI D6 Tool Steel

TiN thin film has been produced on the surface of AISI D6 tool steel by using a titanium interlayer. In this work, the morphology, the microstructure and interface depth profile of TiN films deposited at two substrate temperatures (220 oC and 450 oC) in the coating process are presented and discussed. The AISI D6 tool steel substrates were coated with titanium thin film as the underlayer and with TiN thin film as the top layer. They were deposited by conventional cathodic arc process. The surfaces of TiN films were observed by scanning electron microscopy (SEM). The microstructure of these samples was analysed by X-ray diffractometry (XRD). The influence of the substrate temperature on the TiN film-Ti film-AISI D6 interface region were investigated by energy dispersive spectrometry (EDS) and its cross section were observed using backscattered electron image (BEI). The results showed that TiN films deposited at 220 oC formed a film of strongly (111) preferred orientation, while in 450 oC formed a film of (111) and (220) preferred orientation. The thickness of the TiN films increased with increasing substrate temperature. The results show that the interface region of the TiN film-Ti film-AISI D6 substrate system was significantly improved when higher substrate temperature during deposition is used.

Residual stresses of diamond and diamondlike carbon films

This paper evaluated the internal stresses of different diamond and diamondlike carbon (DLC) coatings. For the diamond coatings, the stresses were determined using micro-Raman spectroscopy and x-ray diffraction (XRD), while the stresses of DLC films were determined with bent plate method. The internal stress was related to the structural properties of the coatings. Direct current plasma jet, combustion flame, and microwave chemical-vapor deposition processes were used to prepare the diamond coatings on the tungsten carbide or molybdenum substrates, while the DLC films were deposited on the silicon wafers with filtered cathodic vacuum arc process. From the Raman spectra of the diamond coatings, the compressive internal stresses were determined, which were related to the microstructure of the coatings. The results from XRD were comparable with those obtained from micro-Raman spectroscopy. Higher compressive residual stresses in the DLC films were noticed, which were also related to their chemical bonding nature as well as their microstructures.

Deposition of nanocomposite TiN-Si3N4 thin films by hybrid cathodic arc and chemical vapor process

A hybrid technique is described for the synthesis of nanocomposite TiNSi3N4 thin films based on the reactive deposition of Ti produced from a cathodic arc source and Si from a liquid tetramethylsilane (TMS), precursor. The technique combines both the physical vapour of Ti and chemical vapour of silicon in a nitrogen background pressure in a single system. The influence of the TMS flow rate on the structure and mechanical properties has been investigated. The film structure was found to comprise of TiN crystallites and amorphous Si3N4. The X-ray diffraction data showed that with increasing TMS flow, there is a decrease in the TiN crystalline size from 33 nm to 4 nm. The hardness of the films was found to be strongly dependent on the Si content and reached a maximum value of 41 GPa at ∼5% Si content at a total pressure of nitrogen and TMS of 0.8 Pa. Hardness enhancement was found to arise from the nanostructural change induced due to the addition of an amorphous Si3N4 phase into the film. Transmission electron microscopy (TEM) analysis confirmed the structure of the ncTiN/aSi3N4 composites. Films with 4 at. % or more silicon were found to maintain the hardness after annealing at 500 °C in vacuum.

Investigation of the properties of Al 1− xCr xN coatings prepared by cathodic arc evaporation

Al 1− x Cr x N coatings prepared by different deposition techniques were investigated in the past, for which excellent oxidation and wear resistance (in comparison to Ti 1− x Al x N-coatings) was found. In this work Al 1− x Cr x N films are deposited from Al 1− x Cr x targets with various composition (0< x<1) by the reactive cathodic arc process. In the current study, chemical composition, crystal structure and mechanical properties like hardness, wear rate and film stress are characterized. For determination of the phase and structure stability at higher temperatures, heat treatments in inert gas atmosphere were carried out. In oxidation experiments, it is shown that with increasing Al-content the oxidation-start temperature shifts to higher values. The different chemical composition and the results of mechanical and chemical characteristics were correlated to cutting test results.

Dual FCVA–PECVD deposition for DLC films

It is now well known that the filtered cathodic vacuum arc (FCVA) process produces ta-C films with good mechanical properties such as very high hardness. On the other hand, PECVD films are often hydrogenated, with good mechanical properties but with low hardness (soft DLC). However, the internal stress of materials, produced by both techniques, is high and restricts the DLC film thickness. A combination of these types of deposition is expected to enlarge the range of mechanical properties of DLC films by producing intermediate sp 3/sp 2 ratios and hardness. In this paper, we demonstrate the incorporation of hydrogen in ta-C films synthesised by mixing FCVA and PECVD. The hydrogen incorporation is realised by introducing a CH 4 flow during the FCVA process. We present in this paper a comparison between ta-C and ta-C:H in terms of average mass density and hardness of the films in order to study the hydrogen influence on structure and properties.