Deposition Of Diamond-like Carbon Thin Films Research Articles

Fabrication of device equipped with rope-like axon bundles by diamond-like carbon thin film patterning deposition

The aim of this research is to fabricate plane-type devices possessing straight longer axons individually and regularly arrayed for evaluating the axon behavior of neuronal cells in vitro toward the development of brain-on-chip models, utilizing diamond-like carbon (DLC) thin film patterning deposition. The DLC thin films were deposited on a polydimethylsiloxane (PDMS) plate with a plasma CVD method under four conditions, with/without stretching of and a metal mask on the plate, and the fabricated substrates were used to culture human neuroblastoma cells, SH-SY5Y, for up to 21 days. In the case of the stretched PDMS plate with the mask covered, extremely peculiar structures were created on the DLC deposited areas of the substrate, with multiple 20 μm-thick rope-like axons aligned straight at the length of millimeter-level at intervals of about 200 μm. It was found that the rope-like axons consisted of plenty of thinner axons, and were supported by the clusters of cells at both ends. It was strongly suggested that the linear wrinkle structures created by the DLC deposition played an important role in the formation of the rope-like axons. This device can be fabricated by means of not conventional lithographic techniques, but only DLC thin film deposition.

Increased body fluid repellency and electrochemical corrosion resistance of intravascular stent materials by ICP-CVD-based DLC thin-film deposition

Intravascular stents face adhesion- and corrosion-based challenges causing In-stent Restenosis (ISR). This study analyzes the influences of thin-film Diamond-Like-Carbon (DLC) deposition on body fluid repellency and corrosion behavior in Simulated Body Fluid (SBF) at 37 °C for intravascular stent materials. The stent specimens of 316 L and 316 LVM stainless steel, Ti-Alloy, and CoCr-Alloy were coated with DLC thin-films by Inductively Coupled Plasma Chemical Vapor Deposition (ICP-CVD). The repellencies of bare and DLC-coated specimens to body fluids, including the blood, plasma, glycerol, and distilled water (DIW) were analyzed by their Contact Angles (CA). Electrochemical impedance spectroscopy (EIS) and corrosion analysis in simulated body fluid were conducted using a potentiostat system. Bare specimens exhibited hydrophilic behavior with 51° CA for distilled water and lower body fluid repellencies with 69°, 64°, and 57° CAs for total blood, blood plasma, and glycerol, respectively. DLC coating improved blood repellency to 88° CA and hydrophobic feature to 81° CA. The electrochemical corrosion analysis exhibited that ICP-CVD based DLC thin-film deposition increased the electrochemical polarization resistance of BMS specimens from 22.02 kΩ.cm2 to 386.6 kΩ.cm2 for 316 L SS, 408.8 kΩ.cm2 for 316 LVM SS, 1703.0 kΩ.cm2 for CoCr-Alloy, and 1748 kΩ.cm2 for Ti-Alloy. The obtained values reduced the corrosion rate from 447.1 μm/year to 0.241 μm/year and the mass loss rate from 357.1 mg/cm2year to 0.165 mg/cm2year. This study concludes that DLC thin-film structures can lower the risk of ISR by adhesion and corrosion inhibition in BMS specimens, and they have a potential application in fluid-repellent and anti-corrosive drug-free stents.

Fabrication of plane-type axon guidance substrates by applying diamond-like carbon thin film deposition

This research aims to fabricate plane-type substrates for evaluating the axon behaviors of neuronal cells in vitro toward the development of brain-on-chip models by applying the functions of diamond-like carbon (DLC) thin film deposition, which helped to eliminate the costly and time-consuming lithography process by utilizing a shadow mask. The DLC thin films were partially deposited on stretched polydimethylsiloxane (PDMS) substrates covered with a metal mask by the plasma chemical vaper deposition method, and using the substrates culture teats with human neuroblastoma cells (SH-SY5Y) were performed. Three patterns of interconnection structures of axons were created on the substrates with disordered and regular linear wrinkle structures with several μm size formed by the depositions. The patterns were characterized by the structure that the aggregations of axons formed on the linear DLC thin film deposited areas were separately placed in regular intervals and connected each other by plenty of axons, which were individually taut in a straight line at about 100 to over 200 μm in length. The substrates expected of uses for evaluation of axon behaviors are available without fabricating guiding grooves by conventional soft lithographic methods requiring multiple stages and their treating times.

Interconnection of Mesenchymal Stem Cells Using Regularly Arrayed Wrinkle Microstructures Fabricated by Diamond-like Carbon Thin Film Deposition

Interconnection of Mesenchymal Stem Cells Using Regularly Arrayed Wrinkle Microstructures Fabricated by Diamond-like Carbon Thin Film Deposition

On the adhesion of diamond‐like carbon coatings deposited by low‐pressure plasma on 316L stainless steel

Diamond‐like carbon (DLC) thin films constitute proven protective coatings due to their outstanding mechanical and tribological properties, combined with a relative chemical inertness and long‐term stability. These make them particularly attractive to protect metallic medical implants from corrosion and erosion. However, lack of adhesion between DLC and metallic surfaces is a recurrent problem due to poor interactions with the native oxide layer. An effective strategy to overcome these adhesion issues consists in building interfacial layers. In this context, in this work, the use of a plasma treatment to generate shallow metallic carbide layers was investigated, to promote DLC adhesion directly on the surface of 316L stainless steel (SS). The metallic carbides presence stabilizes and promotes DLC thin film deposition. The highest adhesion was obtained on samples carburized by methane during 20 min with a bias of −700 V. Furthermore, this led to interface amorphization. In conclusion, this study shows that plasma can provide new insights for overcoming the lack of adhesion of DLC thin films on SS metallic surfaces.

Avaliação de desgaste por perda de massa de sistema extrator de moldes de injeção de termoplásticos revestidos com filme fino de DLC

O presente trabalho tem por objetivo, a deposição de filmes finos de DLC sobre componentes do sistema extrator de moldes de injeção, verificando a influência deste revestimento superficial no desgaste desses componentes, sob diferentes configurações de lubrificação superficial. Para esta avaliação, pinos extratores, atualmente produzidos em aço AISI H13 e nitretados à gás, foram revestidos com um filme fino de DLC (carbono tipo diamante, do inglês Diamond Like Carbon) e buchas extratoras foram confeccionadas em AISI P20 e AISI H13, e, posteriormente, temperadas e revenidas. O filme fino de DLC foi depositado em uma câmara com sistema PECVD (deposição química a vapor assistida por plasma, do inglês Plasma Enhanced Chemical Vapor Deposition) auxiliado por confinamento eletrostático de plasma. Um dispositivo que simula o sistema de extração de um molde de injeção foi utilizado para testar o comportamento ao desgaste dos conjuntos pino-bucha propostos, em função do aumento do número de ciclos. O desgaste nos pinos foi avaliado quantitativamente por perda de massa, após 100.000 ciclos. Os resultados da perda de massa mostram que para as amostras sem utilização de graxa lubrificante, a taxa de desgaste foi consideravelmente menor. Os pinos que menos apresentaram desgaste foram os dos conjuntos PS e HS, ambos sem utilização de graxa, com perda de 5,400 e 5,467 mg, respectivamente. Com isto, ficou evidenciado a possibilidade de utilização de pinos com revestimento de DLC sem a utilização de graxa lubrificante em sistemas extratores de moldes de injeção e que isto ainda propiciou uma redução considerável na taxa de desgaste.

Fabrication of arrayed microwells with wrinkle microstructure by ink-jet and diamond-like carbon thin film deposition process

Fabrication of microwells is an important technology to create and enhance the functions needed for the biological applications of microfluidic devices. In this paper, how to fabricate arrayed microwells on poly(dimethylsiloxane) (PDMS) substrates handily using an ink-jet processing was presented. More, the microwells having wrinkle microstructures with several μm size on the surfaces were fabricated by a combination procedure of the ink-jet and diamond-like carbon (DLC) thin film deposition. The shapes of the microwells were hexagon and circle, and the sizes were in the ranges of 100–170 μm in diagonal or diameter and 3–30 μm in depth. To investigate the effect of the microwells on cellular behaviors, mouse myoblast cells were cultured on the PDMS substrates. The results demonstrated that the microwells with wrinkle microstructures had the ability to form spherically shaped cell aggregates of around 100 μm size, which were considered to be multicellular spheroids.

The influence of gas flow rate on the structural, mechanical, optical and wettability of diamond-like carbon thin films

In this research, diamond-like carbon (DLC) thin films were deposited on silicon substrates by radio-frequency plasma enhanced chemical vapor deposition method using gas mixture of CH4 and Ar. The effect of different CH4/Ar gas ratio on the structure, refractive index, transmission and hardness of the DLC thin films were investigated by means of Raman spectroscopy, ellipsometry, Fourier transform Infrared Spectroscopy and nano-indentation methods, respectively. Nuclear resonant reaction analysis was used to measure the amount of hydrogen and carbon in the thin films. Furthermore, wettability of the thin films was achieved by measuring of water contact angle (WCA). The results indicated that the structural properties of the diamond-like carbon thin films are strongly dependent on the composition of gas mixture. Based on ellipsometry results, refractive index of the thin films varied in the range of 1.89–2.06 at 550 nm. FTIR results determined that deposition of DLC thin films on silicon substrate led to an increase of the light transmission in IR region and these films have the potential to be used in silicon optics as the antireflective coatings in this region. Nano-indentation analysis showed that the thin films hardness changed in the range of 7.5–11 GPa. On the other hand hydrogen content and fraction of C‒H bonds in the samples increased by an increase in the gas ratio of CH4/Ar. Also, WCA measurements indicated that WCA for thin films with gas ratio of 3/7 is the most and equal to 79°.

Partial formation of linear concavo-convex microstructure onto microwells by diamond-like carbon thin film deposition

By a procedure to partially deposit rigid diamond-like carbon (DLC) thin films using a mask on a soft elastomer, poly(dimethylsiloxane) (PDMS), substrate directionally stretched, areas with the regular linear pattern consisting of a periodical concavo-convex shape with several μm size were successfully formed onto microwells fabricated on the substrate. The DLC thin film depositions were performed by an inductively-coupled plasma (ICP) CVD method, and the optimal deposition conditions, mainly the substrate bias voltage of −650V, to form the linear pattern of the periodical concavo-convex shape were revealed. When an elongation strain applied on the PDMS substrate increased, the height of the concavo-convex shape increased. In addition, by an increase in the deposition time both height and width of the concavo-convex shape showed the tendency to increase. A model that the compressive stress arisen from the large mismatch of the elastic moduli between the DLC thin film and the PDMS substrate induces buckling of the film to produce the wrinkled microstructure was in close agreement with the obtained results.

Characteristics of Diamond-Like Carbon Thin Film Semiconductor for Photovoltaic Application

Diamond-Like Carbon (DLC) thin film semiconductors were produced by Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) method and characterized by nanoindentation to investigate its mechanical properties for protective coating applications. The XRD analysis showed that the films were hydrogenated amorphous carbon (a-C:H) nature. The thickness of the films was measured by Ellipsometry and Profilometry. The thickness variation with deposition rate followed a linear relationship within the various deposition parameters showed a good homogeneity formed of DLC films. The hardness value linearly varied with RF power at 30 mTorr showed an optimum pressure to form a quality DLC thin film. The optimum RF power and CM pressure was 150 watt and 30 mTorr showed the thin film hardness 18.73 ± 2.51 GPa and reduced modulus 171.04 ± 11.13 GPa and the films were investigated as hard hydrogenated amorphous carbon (a-C:H) structure. The high hardness value and the deposition parameters showed that the deposition method of RF-PECVD was a controlled deposition process especially for a-C:H DLC thin film deposition. The thickness effects on hardness of the film implied that the optimum deposition condition was an important aspect to get quality DLC films for protective coating application.

Current research and development topics on gas cluster ion-beam processes

This report reviews the developing field of ion-beam technology that employs accelerated ions consisting of clusters of a few hundreds to thousands of atoms (gas cluster ion-beam technology, GCIB). Cluster ion-surface collisions have been found to produce low-energy bombardment effects at very high density, and GCIB processes exhibit unique nonlinear effects that are useful for surface processing applications. The effects include low-energy ion bombardment, lateral sputtering, and low-temperature thin-film formation. GCIB processing has been applied to shallow junction formation; high rate etching; surface smoothing of materials including metals, dielectrics, superconductors, and diamonds; and high-k oxide and diamond-like carbon thin-film deposition. We describe the unique characteristics of GCIB-surface interactions and GCIB process applications for (i) ultrashallow junction formation and doping in Si, (ii) surface smoothing of metals, (iii) selective smoothing of silicon-on-insulator SiC, and other compound semiconductor films, (iv) integrated circuit back-end-of-the-line processing, and (v) high-quality multilayer thin-film formation for reliable and durable optical filters.

Effect of diamond-like carbon thin film deposition on the resistance of polycarbonate to radiation-induced degradation

The effects of high-energy gamma irradiation on the characteristics of polycarbonate specimens (Lexan plate) deposited with a thin film of diamond-like carbon (DLC) were investigated. A plasma enhanced CVD method was adopted in depositing a thin DLC film on the polycarbonate specimens. Both specimens, with DLC film and without it, were exposed to the gamma radiation emitted from a Co-60 source to the level of 10 6 rad for comparing their properties. The concentration of free radicals in the undeposited specimen rapidly decreased to 4.4% of the initial value, while that in the specimen deposited with DLC film remained at 60%. It is suggested that DLC inhibits the oxidation reaction between free radicals and oxygen in the surrounding air. This study shows experimental evidence that the resistance to radiation-induced oxidation of a polymer can be enhanced by depositing a thin layer of DLC.

Optical emission study of the laser plasma plume produced during diamondlike carbon thin film preparation

We have studied the application of the diamondlike carbon (DLC) film as a protective coating layer for high temperature superconducting thin films. Recently, the DLC film was proposed as an attractive material for field electron emitter device. We report on spectroscopic properties of the KrF laser plasma plume produced during the DLC thin film deposition. Optical emission measurements showed appearance of such neutral and ionic species as H, C, C +, CH, CH +, C 2H +. Strong emission from neutral and ionic molecules CH, C 2, C 2H + produced by the reaction in the gaseous phase has been observed with the ambient hydrogen gas pressure increase. The calculated velocities of CH and C 2H + molecules at the distances of 10–20 mm from the target are found to be 5.0×10 3 m/s and 9.1×10 3 m/s, correspondingly. The properties of the DLC thin films are strongly affected by the laser plasma plume dynamics. The DLC film deposited on MgO (100) at room temperature and 200 mTorr hydrogen pressure was almost transparent in the visible light range and had an optical band energy gap of 2.0 eV, which is about half of that of a diamond.

Diamond-like carbon thin film deposition using a magnetically confined r.f. PECVD system

Abstract Diamond-like carbon thin films have been deposited at low temperatures, using local magnetic confinement in a r.f.-powered plasma-enhanced chemical vapour deposition process. The increased plasma density and temperature obtained by magnetically confining the plasma, increases the ionization of the hydrocarbon gas in the deposition chamber. The modified plasma is characterized together with the material properties of the deposited films. A model is proposed to explain the dissociation of species in the plasma and the plasma temperature based on the observed results. Doping of the films using nitrogen gas fed in with the hydrocarbon is also investigated.