Ultrathin Diamond-like Carbon Films Research Articles

Ultra-thin DLC diaphragm-based optical fiber sensor achieving a highly sensitive and broadband acoustic response.

In the design of an extrinsic Fabry-Perot interferometer (EFPI) acoustic sensor, broadband response and high-sensitivity sensing are usually conflicting and need to be carefully balanced. Here, we present a novel, to the best of our knowledge, optical fiber acoustic sensor based on an ultra-thin diamond-like carbon (DLC) film, fabricated using the plasma-enhanced chemical vapor deposition method, and transferred by a surface-energy-assisted method. The sensor exhibits a broadband response ranging from 200 Hz to 100 kHz, maintains an average sensitivity of 457.3 mV/Pa within the range of 6 to 30 kHz, and can detect weak acoustic signals down to 3.23 µPa/Hz1/2@16.19 kHz. The combination of an ultra-thin DLC film with a relatively high Young's modulus and internal stresses results in a trade-off between high sensitivity and a broadband response. This performance demonstrates that our sensor is among the most advanced in the EFPI acoustic sensor family, with significant potential for applications such as photoacoustic spectroscopy, defect diagnosis, and bio-imaging.

Characterization of Ultra-Thin Diamond-Like Carbon Films by SEM/EDX

A novel, high throughput method to characterize the chemistry of ultra-thin diamond-like carbon films is discussed. The method uses surface sensitive SEM/EDX to provide substrate-specific, semi-quantitative silicon nitride/DLC stack composition of protective films extensively used in the hard disk drives industry and at Angstrom-level. SEM/EDX output is correlated to TEM to provide direct, gauge-capable film thickness information using multiple regression models that make predictions based on film constituents. The best model uses the N/Si ratio in the films, instead of separate Si and N contributions. Topography of substrate/film after undergoing wear is correlatively and compositionally described based on chemical changes detected via the SEM/EDX method without the need for tedious cross-sectional workflows. Wear track regions of the substrate have a film depleted of carbon, as well as Si and N in the most severe cases, also revealing iron oxide formation. Analysis of film composition variations around industry-level thicknesses reveals a complex interplay between oxygen, silicon and nitrogen, which has been reflected mathematically in the regression models, as well as used to provide valuable insights into the as-deposited physics of the film.

Dependence of Optimum Thickness of Ultrathin Diamond-like Carbon Coatings over Carbon Nanotubes on Geometric Field Enhancement Factor

The generation of a field emission (FE) cathode electron source has attracted wide attention for its miniaturization, high-frequency operability, and low energy consumption. However, the FE performance of cold cathodes is limited by poor current stabilities of carbon nanotube (CNT) emitters. Coating CNTs with sp3-bonded carbon coatings is considered as a successful approach to stabilize the FE currents. High-quality ultrathin diamond-like carbon (DLC) films, which serve as sp3 carbon coatings, are deposited uniformly on CNTs by filtered cathodic vacuum arc evaporation in this research. The thicknesses of DLC coatings and the field enhancement factors of pristine CNTs affect to a large extent the FE properties. An optimum coating thickness of DLC layers corresponding to the lowest threshold field exists due to space-charge-induced band bending, at which the depletion region of the DLC layer in equilibrium is maximized. The optimum coating thickness increases with the geometric field enhancement factor of p...

Diamond-like carbon as gate dielectric for metal–insulator–semiconductor applications

Diamond-like carbon (DLC) has been studied as a dielectric material for future metal–insulator–semiconductor (MIS) technology. In this paper, ultrathin DLC films were deposited on silicon substrates by using the dc magnetron sputtering technique at various deposition voltages. The current–voltage characteristics indicated that the leakage currents of the MIS devices decreased with an increase in deposition voltages, and that a low leakage current ([Formula: see text] A/cm2) was achieved at −2 V bias voltage. The deposition voltage effects on the structures of films were investigated through Raman spectroscopy, which indicated that the sp3 bonding fraction decreased with an increase in the deposition voltage. The ramp-voltage breakdown test revealed high effective breakdown electric field ([Formula: see text]85 MV/cm) for the MIS device with the DLC film deposited at 1100-V deposition. Stress-induced leakage current measurement indicated that the DLC film exhibited excellent reliability.

Nanomechanical and nanotribological behavior of ultra-thin silicon-doped diamond-like carbon films

Diamond-like carbon (DLC) film with ultra-thin thickness displays high internal stress, thereby resulting in the failure of protection to the substrate. Incorporation of silicon into DLC films, which has higher adhesion to substrate and extraordinary thermal stability, can be potentially used in heat assisted magnetic recording (HAMR). The nanomechanical and nanotribological behavior of Si doped DLC films is investigated using molecular dynamic simulation method. Effects of the Si content and density of Si-DLC films on the frictional behavior and wear resistance of Si-DLC films are investigated. Surface profiles at the contact interface are identified before and after sliding.

Materials Selection for Ultra-Thin Diamond-Like Carbon Film Metrology and Structural Characterization by TEM

Materials Selection for Ultra-Thin Diamond-Like Carbon Film Metrology and Structural Characterization by TEM

Conductive Atomic Force Microscopy Characterization of Ultra-Thin Diamond-Like Carbon Films on Magnetic Recording Heads

Journal Article Conductive Atomic Force Microscopy Characterization of Ultra-Thin Diamond-Like Carbon Films on Magnetic Recording Heads Get access Shirley Mejia, Shirley Mejia Western Digital Corporation, Magnetic Heads Operations, Metrology & Materials Characterization, Ayutthaya, Thailand, 13160 Search for other works by this author on: Oxford Academic Google Scholar Sean P Leary, Sean P Leary Western Digital Corporation, Magnetic Heads Operations, Metrology & Materials Characterization, Ayutthaya, Thailand, 13160 Search for other works by this author on: Oxford Academic Google Scholar Guilherme P Souza, Guilherme P Souza Western Digital Corporation, Magnetic Heads Operations, Metrology & Materials Characterization, Ayutthaya, Thailand, 13160 Search for other works by this author on: Oxford Academic Google Scholar Kurt C Ruthe Kurt C Ruthe Western Digital Corporation, Magnetic Heads Operations, Metrology & Materials Characterization, Ayutthaya, Thailand, 13160 Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 21, Issue S3, 1 August 2015, Pages 1613–1614, https://doi.org/10.1017/S1431927615008843 Published: 23 September 2015

Structural stability of nanometer thick diamond-like carbon films subjected to heating for thermally assisted magnetic recording

In this study, the structural stability of ultra-thin diamond-like carbon (DLC) films subjected to heating was investigated experimentally. The thermal robustness of nanometer thick DLC films for thermally assisted magnetic recording was demonstrated, and their damage mechanisms were elucidated using chemical vapor deposition and filtered cathodic vacuum arc DLC films. In addition, the refractivity of disk substrates with heated DLC thin films was evaluated using a scanning microellipsometer. This measurement system is suggested to be an effective method for evaluating the thermal stability of DLC films. The effect of the heating duration on the thermal stability of DLC films was also investigated by this method. Further, it was suggested that DLC thin films on an air bearing surface may be affected by laser heating because this surface may be heated for a significantly longer duration owing to the magnetic head read/write operation. However, the DLC thin films on the disk substrate may not be affected as severely by laser heating.

Magnetically enhanced plasma coating of nanostructures with ultrathin diamond-like carbon films

Coating using magnetically enhanced plasma deposition gives smooth diamond-like carbon films that increase hardness and wear resistance of nanostructures.

Gas Permeation, Mechanical Behavior and Cytocompatibility of Ultrathin Pure and Doped Diamond-Like Carbon and Silicon Oxide Films

Protective ultra-thin barrier films gather increasing economic interest for controlling permeation and diffusion from the biological surrounding in implanted sensor and electronic devices in future medicine. Thus, the aim of this work was a benchmarking of the mechanical oxygen permeation barrier, cytocompatibility, and microbiological properties of inorganic ~25 nm thin films, deposited by vacuum deposition techniques on 50 µm thin polyetheretherketone (PEEK) foils. Plasma-activated chemical vapor deposition (direct deposition from an ion source) was applied to deposit pure and nitrogen doped diamond-like carbon films, while physical vapor deposition (magnetron sputtering in pulsed DC mode) was used for the formation of silicon as well as titanium doped diamond-like carbon films. Silicon oxide films were deposited by radio frequency magnetron sputtering. The results indicate a strong influence of nanoporosity on the oxygen transmission rate for all coating types, while the low content of microporosity (particulates, etc.) is shown to be of lesser importance. Due to the low thickness of the foil substrates, being easily bent, the toughness as a measure of tendency to film fracture together with the elasticity index of the thin films influence the oxygen barrier. All investigated coatings are non-pyrogenic, cause no cytotoxic effects and do not influence bacterial growth.

The Optical Property and Sensitivity of Ag Nanoparticles Deposited Ultra-Thin Diamond-Like Carbon Films

Ag nanoparticles (NPs) had most prominent local surface plasma resonance effect (LSPR) among the all metals. Diamond-like carbon (DLC) film had good biological compatibility, wear resistance, corrosion-resisting and high transmission ability in the visible and near-infrared range. Since the Ag NPs were easily oxidized in air,a new LSPR interface between them and an ultra-thin DLC films was formed by means of a plasma enhanced chemical vapor deposition (PECVD). The morphologies and properties of the Ag NPs deposited ultra-thin DLC films were studied by using Raman spectrometer, X-ray photoelectron spectrometer (XPS) , field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) and so on. And the optical tramsmission sensitivity of the new LSPR interface was also examined. The results indicated that the DLC films deposited in a shorter time had a higher sp3bond content of carbon atoms and more sensitive to refractive index of surrounding media. Moreover, to obtain the optimal morphologies and the sensing property, the deposition time for forming the DLC films should be controlled within 30 seconds.

Study on the Preparation of Silver Nanoparticles Coated with Diamond-Like Carbon Film and their Properties

Ag nanoparticles (NPs) have prominent local surface plasma resonance effect (LSPR), and Ag NPs exhibit sharpest and strongest bands among all metals. Diamond-like carbon (DLC) film have good biological compatibility and also have high transmissibility in the visible and near-infrared region. A new LSPR interface between Ag NPs and ultra-thin DLC film was formed by Plasma Enhanced Chemical Vapor Deposition. The morphologies and properties of the Ag NPs coated with DLC film were studied with SEM and AFM. The results indicated that the thickness of DLC film increased with the deposition time. LSPR peak became sharper after depositing for 1 or 2 min. DLC film was prior to nucleate on the surface of Ag NPs, and it has high content of sp2 bonds near the interface. The sensitivity of new LSPR interface deposited for 20s was about the half of the sensitivity of bare Ag NPs and the sensitivity significantly decreased with deposition time. This result is helpful to understand the behavior of the new LSPR interface and to improve its sensitivity.

B-2-4 熱アシスト磁気記録におけるヘッドディスクインターフェイスに関する研究 : DLC保護膜の構造におよぼす加熱の影響(B-2 ヘッド・ディスク・インタフェースに作用する相互作用他,口頭発表:ヘッド・ディスク・インターフェイス)

To further increase recording density of disk storage drives, thermally-assisted magnetic recording can solve the fundamental issues of thermal fluctuation and is regarded as the key technology for achieving recording density of more than 1 Tb/in^2. In this technology, it is suggested that there is critical issues for the ultra-thin liquid lubricant films and diamond-like carbon (DLC) films on the disk surfaces, because they are heated to high temperature with laser beams. In this study, we focused on the thermal stability of the three types of DLC films deposited by chemical vapor deposition (CVD), ion beam deposition (IBD) and filtered cathodic vacuum arc (FCVA) deposition. We also compared the optical properties of heated three DLC films characterized by ellipsometry, electron spectroscopy for chemical analysis and raman spectroscopy. As a result, the effects of heating temperature on the structure of DLC films were clarified.

Effect of thickness on structures of ultrathin diamond-like carbon films

Diamond-like carbon (DLC) films with different thickness were deposited by filtered cathode vacuum arc (FCVA). Vis-Raman and spectroscopic ellipsometry were employed to analyze the structure of DLC films. The wavelength of Vis-Raman is 514.5 nm. Experimental results show that structures of DLC films are affected by film thicknesses. When the film thickness increases from 2 to 30 nm, the G-peak position (G-pos) shifts to higher wavelength, the intensity ratio ID/IG and the extinction coefficient Ks decrease. It is indicated that the content of sp3 bond increases with film thickness. However, when the film thickness increases from 30 nm to 50 nm, ID/IG and Ks increase. The content of sp3 bonds decreases with film thickness.

Ultrathin Diamond-like Carbon Film Coated Silver Nanoparticles-Based Substrates for Surface-Enhanced Raman Spectroscopy

We have demonstrated that by coating with a thin dielectric layer of tetrahedral amorphous carbon (ta-C), a biocompatible and optical transparent material in the visible range, the Ag nanoparticle-based substrate becomes extremely suitable for surface-enhanced Raman spectroscopy (SERS). Our measurements show that a 10 A or thicker ta-C layer becomes efficient to protect the oxygen-free Ag in air and prevent Ag ionizing in aqueous solutions. Furthermore, the Ag nanoparticles substrate coated with a 10 A ta-C film shows a higher enhancement of Raman signals than the uncoated substrate. These observations are further supported by our numerical simulations. We suggest that biomolecule detections in analytic assays could be easily realized using ta-C-coated Ag-based substrate for SERS especially in the visible range. The coated substrate also has higher mechanical stability, chemical inertness, and technological compliance, and may be useful, for example, to enhance TiO(2) photocatalysis and solar-cell efficiency by the surface plasmons.

Structure of Ultra-Thin Diamond-Like Carbon Films Grown with Filtered Cathodic Arc on Si(001)

The structure of 3 nm and 15 nm diamond-like carbon films, grown on Si(001) by filtered cathodic arc, was studied by angle-resolved X-ray photoelectron spectroscopy (ARXPS) and transmission electron microscopy (TEM). The ARXPS data was deconvolved by employing simultaneous-fitting, which allowed for a clear deconvolution of the Si 2p and C 1s spectra into their different chemical contributions. An analysis of the take-off angle dependence of the peak intensities allowed for an independent identification of the physical origin of the chemical species. It was shown that the C 1s peak at 283.3 eV and the Si 2p peak at 99.6 eV correspond to SiC, and that the C/Si interface of the 3 nm film consists of a stoichiometric approximately 1 nm SiC layer. To quantify the sp(3)-sp(2) ratio it was necessary to take into account not only their associated C 1s XPS-peak intensities, but also their take-off angle dependence. The thickness of the films obtained through ARXPS closely agrees with cross-sectional TEM images.

The protective properties of ultra-thin diamond like carbon films for high density magnetic storage devices

With the increase of magnetic storage density, the thickness of the protective diamond like carbon (DLC) film on the surfaces of head and disk is required as thin as possible. In this paper, the structure, mechanical properties and corrosion and oxidation resistance of ultra-thin DLC films are investigated. The ultra-thin DLC films were deposited by using filtered cathodic vacuum arc (FCVA) technique. The exact thickness of the ultra-thin DLC film was determined by high resolution transmission electron microscope (HRTEM). Raman analysis indicates that the ultra-thin DLC film presents ta-C structure with high sp 3 fraction. In the wear test, a diamond tip was used to simulate a single-asperity contact with the film surface and the wear marks were produced on the film surface. The wear depths decrease with film thickness increasing. If the film thickness was 1.4 nm or above, the wear depth was much lower than that of Si substrate. This indicates that the ultra-thin DLC film with thickness of 1.4 nm shows excellent wear resistance. Corrosion tests in water and oxidation tests in air were carried out to investigate the diffusion barrier effect of the ultra-thin DLC films. The results show that the DLC film with thickness of 1.4 nm provides adequate coverage on the substrate and has good corrosion and oxidation resistance.

Parametric Studies of Pulsed Laser Deposition of Indium Tin Oxide and Ultra-thin Diamond-like Carbon for Organic Light-emitting Devices

Device quality indium tin oxide (ITO) films are deposited on glass substrates and ultra-thin diamond-like carbon films are deposited as a buffer layer on ITO by a pulsed Nd:YAG laser at 355 nm and 532 nm wavelength. ITO films deposited at room temperature are largely amorphous although their optical transmittances in the visible range are > 90%. The resistivity of their amorphous ITO films is too high to enable an efficient organic light-emitting device (OLED), in contrast to that deposited by a KrF laser. Substrate heating at $200^{\circ}C$ with laser wavelength of 355 nm, the ITO film resistivity decreases by almost an order of magnitude to $2{\times}10^{-4}\;{\Omega}\;cm$ while its optical transmittance is maintained at > 90%. The thermally induced crystallization of ITO has a preferred directional orientation texture which largely accounts for the lowering of film resistivity. The background gas and deposition distance, that between the ITO target and the glass substrate, influence the thin-film microstructures. The optical and electrical properties are compared to published results using other nanosecond lasers and other fluence, as well as the use of ultra fast lasers. Molecularly doped, single-layer OLEDs of ITO/(PVK+TPD+ $Alq_3$ )/Al which are fabricated using pulsed-laser deposited ITO samples are compared to those fabricated using the commercial ITO. Effects such as surface texture and roughness of ITO and the insertion of DLC as a buffer layer into ITO/DLC/(PVK+TPD+ $Alq_3$ )/Al devices are investigated. The effects of DLC-on-ITO on OLED improvement such as better turn-on voltage and brightness are explained by a possible reduction of energy barrier to the hole injection from ITO into the light-emitting layer.

Growth of ultrathin diamond-like carbon films by C 60 cluster assembly: Molecular dynamics simulations

The deposition of C 60 clusters to produce cluster-assembled ultrathin diamond-like carbon (DLC) films is investigated using the molecular dynamics (MD) simulations. The deposition dynamics, especially the fragmentation process of the C 60 cluster are studied. The trajectory and instantaneous velocity of each atom in the cluster reveal a close relationship between cluster deposition and atom-by-atom deposition of DLC film. The atomistic structures, sp 3 fractions, and radial distribution functions of DLC films are quantitatively studied. For relatively low energies ( E < 20 eV/atom), the C 60 structural features preserve partially. The cluster-assembled films show big cavities, non-uniform structures, and rough surfaces. For relatively high energies ( E > 20 eV/atom), the films turn out to be structurally amorphous, densely-packed and sp 3 dominated. A marked discrepancy is observed between the sp 3 fraction of cluster and atom-by-atom deposited DLC films. The kinetic energy dissipation and the oblique incidences of freed atoms are the main reason for this discrepancy.

Effect of substrate morphology on the roughness evolution of ultra thin DLC films

The effect of substrate roughness on growth of ultra thin diamond-like carbon (DLC) films has been studied. The ultra thin DLC films have been deposited on silicon substrates with initial surface roughness of 0.15, 0.46 and 1.08 nm using a filted cathodic vacuum arc (FCVA) system. The films were characterized by Raman spectroscope, transmission electron microscope (TEM) and atomic force microscopy (AFM) to investigate the evolution of the surface roughness as a function of the film thickness. The experimental results show that the evolution of the surface morphology in an atomic scale depends on the initial surface morphology of the silicon substrate. For smooth silicon substrate (initial surface roughness of 0.15 nm), the surface roughness decreased with DLC thickness. However, for silicon substrate with initial surface roughness of 0.46 and 1.08 nm, the film surface roughness decreased first and then increased to a maximum and subsequently decreased again. The preferred growth of the valley and the island growth of DLC were employed to interpret the influence of substrate morphology on the evolution of DLC film roughness.