Characteristics of phosphorus-doped diamond-like carbon films synthesized by plasma immersion ion implantation and deposition (PIII and D)

Plasma immersion ion implantation and deposition (PIII and D) is an effective approach to synthesize high quality thin films for different industrial applications. This dual implantation and deposition process can produce a graded layer that mitigates delamination and poor adhesion. In this work, phosphorus-doped diamond-like carbon (DLC) films were synthesized by PIII and D. Thin DLC films with various phosphorus concentrations were produced by using different experimental parameters. The chemical composition was determined by X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). Micrographs obtained by cross-sectional transmission electron microscopy (X-TEM) reveal good adhesion between the films and substrates. The biocompatibility was evaluated using platelet adhesive tests. The results show that the sample doped with an optimal amount of phosphorus exhibits less platelet adhesive and activation, and the overall results are better than that observed on low-temperature isotropic pyrolytic carbon (LTIC). Phosphorus-doped DLC films thus have potential applications in blood contacting medical devices.     

Effect of negative pulsed high-voltage-bias on diamond-like carbon thin film preparation using capacitively coupled radio-frequency plasma chemical vapor deposition

Mechanical properties of diamond-like carbon films by an effective addition of negative pulsed high-voltage-bias have been investigated in capacitively coupled CH₄/Ar radio-frequency plasma. The results revealed that hardness and elastic modulus of the deposited film, estimated from nano-indentation load-displacement curve for about 1 μm-thick films, increase with the increase of the absolute value of high-voltage V_NPHV for V_NPHV < 5 kV and then saturate. Elastic recovery R got the highest value (> 90%) at V_NPHV = 5 kV.     

Parametric study of nitrided AISI 304 austenite stainless steel prepared by plasma immersion ion implantation

This paper investigates the characteristics of plasma immersion nitrogen-ion implanted AISI 304 austenite stainless steel against such processing parameters as bias voltage (5-20 kV), substrate temperature (300-500 °C), and implantation fluence (1.4 × 10¹⁸-4.2 × 10¹⁸ cm^− 2). Characteristics of the as-implanted specimens under investigation included elemental depth profile, hardness depth profile, crystallographic structure, and corrosion behavior and were determined using glow discharge spectrometry (GDS), the Vickers hardness tester, X-ray diffractometry (XRD), and the potentiodynamic polarization test, respectively. The results show that nitrogen depth profiles strongly depend on these processing parameters and closely relate to the corresponding chromium depth profiles. The hardness depth profiles increase and widen as substrate temperature, bias voltage, and implantation fluence increase. In particular, an improvement in hardness is accompanied by a reduction in corrosion resistance when substrate temperature reaches 500 °C. The corrosion-resistance degrader, CrN, precipitates as substrate temperature exceeds 450 °C, a phenomenon which is clearly evident in the chromium depth profiles as well as the XRD results.     

Behavior of endothelial cells on micro-patterned titanium oxide fabricated by plasma immersion ion implantation and deposition and plasma etching

Titanium oxide films synthesized by plasma immersion ion implantation and deposition (PIII&D) were micro-patterned using argon plasma etching. Wells containing organized arrays of square holes of different depths separated by gaps of 25 μm were produced on the surface of the titanium oxide by etching for 30, 60, 90, and 120 min. The surface wettability and tension of the samples were evaluated. Human umbilical vein endothelial (HUVE) cells were cultured on both smooth and patterned surfaces. The effects of surface micro-patterning on the behavior of the HUVE cells were investigated. Our results show that the titanium oxide prepared by PIII&D has good cyto-compatibility and the micro-patterns influence both the surface energy and cell behavior. Our results demonstrate the feasibility of using micro-patterned surfaces to modulate HUVE cell behavior.     

Investigation of cytocompatibility of surface-treated cellulose nitrate films by using plasma immersion ion implantation

The alpha-particle sensitive colorless cellulose nitrate films (commercially available as LR 115 films from DOSIRAD, France) have been proposed as cell-culture substrates for alpha-particle radiobiological experiments. Cytocompatibility of the substrate is a key factor to the success of such experiments. The present work aims to investigate the cytocompatibility of surface-treated cellulose nitrate films by using plasma immersion ion implantation-deposition. The films were placed in a vacuum chamber, into which nitrogen gas was continuously bled and where the pressure was kept at 2 × 10^− 3 Torr. Implantation was carried out by igniting the nitrogen plasma at 100 W radio-frequency and applying high bias voltage in pulse with 20 μs pulse width and 50 Hz (with 20 kV or no voltage). HeLa cervix cancer cells were then cultured on both the plasma-treated and untreated cellulose nitrate films. Our tests showed that the plasma-treated films are in general more cytologically compatible.     

Secondary electron suppression in nitrogen plasma ion implantation using a low DC magnetic field

Experiments aiming at the reduction or even total suppression of secondary electrons during the plasma immersion ion implantation were carried out using a plasma device with low DC magnetic field. Comparison of ion implantations in B = 0 and another case with B = 43 G, indicated that the magnetic field was effective to suppress SE flow in the direction transversal to B but only partial suppression was attained in the longitudinal direction. However, these results are already significant since the efficiency of implantation was increased and the flow of SE to the walls became localized to the regions with B crossing the walls.     

Fabrication and characteristics of novel microelectronic structures fabricated by plasma-based techniques

A number of novel microelectronic structures have recently been produced using plasma-based techniques such as plasma immersion ion implantation (PIII) and this paper describes the recent progress made in this area in our laboratory. Conventional silicon-on-insulator (SOI) substrates utilizing a buried silicon dioxide layer suffer from self-heating effects as device dimensions shrink to the deep-submicrometer regime. Novel SOI structures using dielectric materials with higher thermal conductance such as aluminum nitride and diamond-like carbon have been produced. In the area of high-k (dielectric constant) thin films, plasma nitridation conducted on materials such as zirconium dioxide improves the recrystallization and interfacial properties. In the conventional Smart-Cut™ or ion-cut technique, high-energy hydrogen implantation is performed to effect layer transfer. Low-energy (several hundred eVs) plasma hydrogenation has recently been conducted in conjunction with damage engineering to produce wafer splitting for layer transfer. This new process allows more flexible control of the depth of hydrogen accumulation and the location of layer cleavage.     

Synchronous plasma enhancement in RF-driven plasma source for ion implantation

We report an original method to increase periodically the plasma density in RF-driven plasma source for surface treatment of materials by ion implantation. The method consists of supplementary injection of ions, electrons and metastable atoms into the processing RF plasma using very short high voltage pulsed discharges applied on a separate electrode at the same repetition rate as the negative accelerating pulses applied on the target. Thus plasma density is periodically increased by an order of magnitude so that the synchronized negative pulses applied on the target for ion implantation find a background plasma about 10 times denser. The advantages of this new method were revealed by nitrogen implanted tests on copper and brass samples.     

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.     

等离子体基离子注入沉积DLC膜的划擦行为

采用等离子体基离子注入沉积技术以乙炔和氢气为气源,在造币模具钢表面制备了类金刚石碳(DLC)膜.采用划痕试验研究了在不同工艺参数下制备的DLC膜在与钢基体的结合力及其变化规律.结果表明,DLC膜临界载荷随着注入电流增加和注入电压降低而增加;随着C2H2/H2比例的增加,临界载荷先增加后减小;随着气压的增加,临界载荷也表现出先增加后减小的趋势.结合SEM分析结果对DLC膜剥落机制进行了探讨,表明DLC膜在划擦过程中首先发生膜和基体之间的层裂剥离,然后在垂直载载作用下发生破裂.     

全方位离子注入与沉积类金刚石碳膜的结构与性能

用等离子体浸没离子注入与沉积(PIIID)复合强化新技术在AISI440C不锈钢表面制备了类金刚石(DLC)碳膜。膜层表面的原子力显微镜(AFM)形貌显示出DLC膜结构致密均匀。Raman光谱分析结果表明,制备的DLC主要是由金刚石键(sp3)和石墨键(sp2)组成的混合无定形碳膜,且sp3键含量大于10%。以纯石墨棒做阴极,C2H2为工作气体条件下合成的DLC薄膜中,sp3键含量总体上较单纯用石墨作阴极而无工作气体条件下合成的DLC薄膜中sp3键含量高。与基体相比,薄膜试样的显微硬度和摩擦磨损性能均得到了较大改善,最大硬度提高88.7%,磨损寿命延长超过4倍。     

Enhanced tribological properties of PECVD DLC coated thermally sprayed coatings

This research investigates the enhancement of the tribological properties of various thermally-sprayed coatings (APS Ni-50Cr, APS Al₂O₃-13%TiO₂ and HVOF WC-17Co) on steel substrate, achieved through the deposition of a thin DLC-based film. Higher adhesive strength between thin films and thermally-sprayed coatings compared to the simple thin film/carbon steel system was found by scratch testing. Dry sliding ball-on-disk tests performed under lower contact pressure conditions (5 N normal load, 6 mm diameter alumina ball) indicated a significant decrease in wear rates and friction coefficients of thermally-sprayed coatings when the thin DLC-based film is employed; little differences exist between the tribological behaviour of the various thin film/thermal spray coating systems and that of DLC-based film on carbon steel. Under higher contact pressure conditions (10 N normal load, 3 mm diameter alumina ball), the thin film/WC-Co system exhibited the best wear performance. These results indicate the superior tribological performance of DLC/thermal spray coating systems, especially under severe contact conditions.     

Incident ion fluence gradients on the front and backside of flat samples

Plasma immersion ion implantation (PIII) is ideal for fast and efficient treatment into three-dimensional objects, as shown by experiments and simulations. In this presentation, a direct comparison of implantations into the front and backside of flat sample (disc, square and rectangle) at 5-15 kV pulse voltage with argon ions is performed with the spatial distribution of the incident ion fluence measured by spectroscopic ellipsometry on SiO₂/Si coupons. A strong influence of the supporting rod for the fluence distribution on the backside of the low symmetry samples, i.e. square and rectangle was observed, in contrast to no influence for the disc sample.     

Effects of pulse parameters on macro-particle production in pulsed cathodic vacuum arc deposition

The effects of the pulse parameters on the production of macro-particles in vacuum arc deposition are studied. A power supply that can provide either direct current or pulsed power is used and the influence of the current and duty cycle are independently investigated. Copper is used as the cathode and glass is used as the substrate. Optical microscopy and scanning electron microscopy with image processing software are used to analyze the macro-particles deposited on the substrate. Our results show the general trend that the density of macro-particles increases with the direct current but there is no obvious correlation with the duty cycles. The lowest degree of macro-particle contamination is observed at a duty cycle of about 40.5%.     

Effects of pulsing frequencies on macro-particle contamination during pulsed vacuum arc deposition

Offering high deposition rates and being suitable for thin film fabrication, vacuum arc deposition (VAD) has been investigated extensively. However, macro-particles (MPs) emitted from the vacuum arc degrade the properties of the deposited samples and various types of magnetic filters have been proposed to mitigate macro-particle contamination. Unfortunately, the resulting deposition efficiency is inevitably compromised. In this work, we used a direct current (DC) based pulsed vacuum arc to deposit copper on a glass substrate. DC ensures continuous arc burning to achieve better stability, and the pulsed power provides high instantaneous and discontinuous energy that affects the generation of MPs. Four sets of experiments were done, and the relationship between the pulsing frequencies and MPs deposited on the substrate was studied. Our results show that the MPs tend to be smaller when the pulsing frequency increases, and the MP ratios vary with the pulsing frequencies in a different way than duty cycles. Several factors related to this phenomenon are discussed.     

Functional inorganic films fabricated by PIII(-D) for surface modification of blood contacting biomaterials: Fabrication parameters, characteristics and antithrombotic properties

One of the important considerations of antithrombotic biomaterial improvement is to control the response of blood cells and plasma proteins to the materials. Material surface characteristics can be suggested as the important factors that influence the response of blood to materials. Thus, modifying the surface characteristics of a material becomes an important way to endue it with the antithrombotic function of preventing blood cell/plasma protein activation. This article is going to summarize results from previous studies on functional inorganic films coated with blood contacting biomaterials, including fabricating condition, characteristics and antithrombotic function. The functional inorganic films of Ti-O, a-C:N:H and Si-N synthesized using PIII-D on the surface of a biomaterial can endue it with the antithrombotic function of preventing platelet adhesion/activation. The characteristics of the films changed with alteration of the fabrication condition and influenced their antithrombotic function strongly. The in vitro test results showed that improved biomaterial surfaces with special antithrombotic function can be obtained from the optimization of the fabrication condition according to the understanding of the blood-materials interaction.     

Study of adhesion of TiN grown on a polymer substrate

TiN films were deposited on polycarbonate substrates by cathodic vacuum arc using the plasma immersion ion implantation and deposition (PIII&D) method. The biaxial intrinsic stress in the film deposited using PIII&D with 3 kV applied bias was 0.3 GPa — much lower than that found in films deposited without the application of high-voltage pulsed bias. It was found that the dominant mechanism for generating stress in the TiN film was thermal stress arising from the large difference between the thermal expansion coefficient of TiN and that of the polymer. Tensile testing was used to ascertain film adhesion and a model was used to estimate the adhesion between the film and the substrate. It was found that PIII&D strongly reduced the stress in the TiN film and increased the adhesion to the polycarbonate. The ultimate shear strength of adhesion is of the same order of magnitude as that of TiN on stainless steel.     

Negative impacts of diamond magnetism on the microstructure of co-deposited composites and the effective solution

In a paper, we reported that incorporation of diamond into composite coatings could cause microstructural deteriorations (e.g., roughening the coating surface, coarsening the matrix grain and reducing the mechanical retention of diamond grains in the matrix), and suggested that all the impacts were caused by diamond magnetism resulting from metallic inclusions trapped in it. To confirm this, further microstructural observations were conducted on composites containing diamond particles that experienced different treatments before being planted, i.e., magnetization (strengthening diamond magnetism by a strong magnet) and demagnetization (weakening diamond magnetism by an alternating magnetic field), as well as on composites fabricated in the presence of an external alternating magnetic field in the vicinity of the cathode. It is shown that advance demagnetization treatment reduces the impacts while advance diamond magnetization treatment does the opposite. Moreover, the impacts could be more effectively reduced by superimposition of the external alternating magnetic field which may exert effects not only on demagnetization of the diamond grains, but also on cations' deposition process since the external magnetic field is much stronger than that produced by diamond.     

Influence of ion-bombardment-energy on thin zirconium oxide films prepared by dual frequency oxygen plasma sputtering

Thin ZrO₂ films were prepared using dual frequency oxygen reactive plasma sputtering for wear-resistance coating of ceramics products. Influences of ion-bombardment-energy E_i were investigated for improvement of film characteristics. The results revealed that the deposition rate and the hardness of the prepared ZrO₂ thin films gradually increased with increasing E_i for E_i < 220-250 eV and then decreased, whereas the water-contact-angle on ZrO₂ thin films was about 90 °, having a good water-repellent nature.