Optical Properties Of Diamond-like Carbon Films Research Articles

Effect of Silver Clusters Deposition on Wettability and Optical Properties of Diamond-like Carbon Films

In this study, the effect of silver clusters deposition was investigated on optical, wettability and surface properties of diamond-like carbon (DLC) films. Silver clusters and DLC films were deposited on Ni-Cu (70.4-29.6;W/W) alloy substrates by ion beam sputtering deposition (IBSD) technique. Optical and structural properties were measured using UV-visible spectroscopy and Raman spectroscopy, respectively. The wettability and surface free energy of films were determined by the contact angle (CA) measurements. Raman spectra of DLC thin film with 121±6nm thickness without accumulated Ag showed that the size of the graphite crystallites with sp 2 bands (La) was 3.36A by the ID/IG ratio equal to 0.062 with large optical band gap equal 3eV extracted from Tauc relation. The results of the deposition Ag in the various ion beam energy between 0.6 to 2keV showed the Ag clusters were accumulated uniformity on the surface of DLC films at 0.9keV. The volume percentage of silver clusters was varied from 5.0±2.01 to 16.3±1.4. The variation was caused by controlling the screen voltage and the deposition time. The CA of the deposited films increases from 79°±2 to 95°±2 as well as the reflection values in the visible and near-infrared region due to the increase in the Ag concentration in the surface of DLC films; while the surface free energy decrease from 86±1 to 66±2mJ/m2 and the optical transmittance is almost constant. Our results demonstrate that the deposition of silver particles on DLC films is potentially useful for biomedical applications having good hydrophobic characteristics without causing a destructive effect on the optical properties of DLC films.

The correlation between optical and mechanical properties of amorphous diamond-like carbon films prepared by pulsed filtered cathodic vacuum arc deposition

Diamond-like carbon (DLC) films were deposited by pulsed filtered cathodic vacuum arc (FCVA) deposition. The microstructure, mechanical and optical properties of DLC films have been investigated as functions of the variation in the substrate negative direct current bias voltage (Vbias) from 0.0 to 1.5 kV. Raman and X-ray photoelectron spectroscopy results show a correlation between the ID/IG ratio and the microstructure in terms of the sp3/sp2 ratio to Vbias. This fact shows that a significant change in the sp3 content, which is attributed to the transformation from graphite-like to diamond-like, is accompanied by a decreasing ID/IG ratio. The relatively high mass density of the films in the range of 2.51 to 2.79 g/cm3 can be obtained with biasing. The mechanical properties, i.e., the hardness and elastic modulus, were 13–25 and 114–145 GPa, respectively. The improvement of the mechanical properties is due to the formation of the compressive residual stress and the local density depending on Vbias. The relationship between the refractive index and the ID/IG ratio agree well with the microstructure and mechanical properties of DLC films. All of these results indicate a vital role of Vbias in determining the DLC properties.

Influences of Pulse Frequency on Structure and Mechanical Properties of DLC Films Synthesized by Pulsed Cathodic Arc Evaporation

Diamond-like carbon (DLC) films were prepared on the Si (100) substrates by pulsed cathodic arc plasma. The influences of given pulse frequency on the microstructure, morphology, mechanical and optical properties of DLC films were investigated by Raman spectroscopy, atomic force microscopy, Knoop sclerometer, X-ray double-crystal surface profilometer. The results showed that the variation of pulse frequency could significantly change the microstructure of DLC films, including the size and ordering of sp2carbon clusters and movement or diffusion of carbon atoms. The increasing of pulse frequency led to the variation of the relative fraction of Csp3/Csp2. The hardness and internal stress of the DLC films were affected accordingly. The results might contribute to the synthesis of DLC films with excellent structure and properties by cathodic arc evaporation.

Frictional and Optical Properties of Diamond-Like-Carbon Coatings on Polycarbonate

In this work, diamond-like-carbon (DLC) films were deposited onto polycarbonate (PC) substrates by radio-frequency plasma-enhanced chemical vapor deposition (RF PECVD), and silicon films were prepared between DLC and PC substrates by magnetron sputtering deposition so as to improve the adhesion of the DLC films. The deposited films were investigated by means of field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Subsequently, the following frictional and optical properties of the films were measured: the friction coefficient by using a ball-on-disk tribometer, the scratch hardness by using a nano-indenter, the optical transmittance by using a UV/visible spectrometer. The effects of incident power upon the frictional and optical properties of the films were investigated. Films deposited at low incident powers showed large optical gaps, which decreased with increasing incident power. The optical properties of DLC films correlated to the sp2 content of the coatings. High anti-scratch properties were obtained at higher values of incident power. The anti-scratch properties of DLC films correlated to the sp3 content of the coatings.

The Optical Properties of DLC Films Processed by Laser Radiation

Diamond-like carbon (DLC) films have being widely applied in various domains owing to their excellent optical and mechanical properties, chemical inertness and bio-compatibility[1,2]. But it generally exhibits low a laser induced damage threshold (LIDT).As to infrared protective films, DLC films were asked to be a high laser damage threshold. So far, the real reason of laser damage is unclear. In order to understand the real reason of the laser damage, it is necessary to deeply research the relationship between optical properties and laser radiation. In this paper, optical properties post irraditing by various laser energy were inverstigated. Hydrogen-free amorphous carbon films were deposited by unbalanced magnetron sputtering with a graphite target on Si substrate in this paper. The DLC films were radiated with raster scans methods by a 1064nm and 8–10 ns laser in this work. The transmittance, refractive index, extinction coefficient and surface morphology of DLC before and after radiation were examined by fourier transform infrared spectrometer, ellipsometer and talysurf respectively. The influences were considered as function of laser energy density.The optical properties before and after laser radiation were compared. It is found that as laser fluences rise from 0 to 0.5 J/cm2, the transmittance peak reduce from 67.06% to 58.27%, the refractive index decrease from 1.88 to 1.67(λ=1200), the extinction coefficient increase from 0.07 to 0.32(λ=1200), and the surface roughness become 149.28nm in this procedλure. Especially, the reasons of change were expounded in this paper.

Optical properties of diamond‐like carbon films irradiated by X‐ray photons

AbstractAmorphous diamond like carbon (DLC) films deposited at room temperature on quartz glass wafer by means of direct ion beam deposition method from acetylene gas or hexamethyldisiloxane (HMDSO) vapour mixture with hydrogen and nitrogen gas were irradiated by high energy X‐ray photon and the optical properties of irradiated DLC films were investigated. Ionizing radiation induced modification of optical properties of the DLC films of different type were studied using UV–VIS spectrometry, laser ellipsometry, Raman and IR spectroscopy, and interpreted on the basis of the obtained results. It was found, that the irradiation of amorphous hydrogenated DLC films introduced significant changes in the investigated structures; however the properties of SiOx containing DLC films remained almost stable after their exposure with high energy X‐ray photons. The influence of film deposition conditions and co‐doping on the optical properties of irradiated DLC films and the role of hydrogen in the films are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The effect of annealing on the properties of diamond-like carbon protective antireflection coatings

In addition to its similarity to genuine diamond film, diamond-like carbon (DLC) film has many advantages, including its wide band gap and variable refractive index. Therefore, as one of the diverse applications, DLC film can be utilized as a protective coating for IR windows and an anti-reflective coating for solar cells. For this study, DLC films were prepared by the radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) method on silicon substrates using methane (CH 4) and hydrogen (H 2) gas. We examined the effects of the post-annealing temperature and the annealing ambient on structural, electrical and optical properties of DLC films. The films were annealed at temperatures ranging from 300 to 900 °C in steps of 200 °C using rapid thermal annealing equipment in nitrogen ambients. The thickness of the film was observed by scanning electron microscopy (SEM) and surface profile analysis. The variation of structure according to the annealing treatment was examined using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The reflectance of DLC thin film was investigated by UV–vis spectrometry and its electrical properties were investigated using a four point probe and I– V meter. The carrier lifetime of the film was also checked.

Optical properties of DLC films deposited by the saddle field fast atom neutral beam source

A saddle field fast atom beam source (FAB) was used to produce diamond-like carbon (DLC) coatings on glass substrates by dissociation and ionisation of acetylene (C 2H 2) in a low pressure vacuum. The UV absorbance of deposited films was measured by UV–vis spectrometer. The optical band gap E g, of these films was measured by Tauc formula as a function of deposition current and pressure. The UV absorption of DLC films was found lower for the whole wave number range (400–1100 nm) at lower deposition current 0.4 A, whereas the UV absorption with photon energy does not appear to depend at deposition pressure level particularly for higher deposition current. The value of optical band gap of films was found higher for higher deposition current 0.8 A. The sp 3 content inside the film was found to be higher with higher deposition current which affected the optical band gap.

Mechanical and Optical Properties of DLC Films Prepared by DC-Magnetron Sputtering Using Sintered Diamond Target.

Diamond-like carbon (DLC) film has outstanding properties, such as high hardness, chemical resistance, and low friction coefficient under various conditions ; however, DLC films deposited by conventional methods still have a problem in low optical transmittance due to sp2 carbons remaining in the film. This paper describes sputtering deposition of DLC films using a sintered diamond target, which consist of sp3 carbons. Mechanical and optical properties of the DLC films were discussed in comparison with the DLC films prepared using a graphite target, and it was found that not only the hardness but also the transmittance of the DLC film grown from a sintered diamond target were higher than that for a film grown from a graphite target. These results indicate that the target material has the strong effect on the properties of DLC films, and high-quality DLC films can be prepared using a sintered diamond target.